One-generation reproductive toxicity study of dietary 17beta-estradiol (E2; CAS No. 50-28-2) in CD-1 (Swiss) mice

There is no information on reproductive/developmental effects in mice from dietary estrogen. Therefore, 10 adult CD-1^® mice/sex/group were administered dietary 17β-estradiol (E2) at 0, 0.005, 0.05, 0.5, 2.5, 5, 10, and 50 ppm for 2-week prebreed, mating, gestation, lactation. F1 weanlings (3/sex/litter) were necropsied and 2/sex/litter were retained, with exposure, until vaginal patency (VP) or preputial separation (PPS) and then necropsied.

Results included complete infertility at 2.5–50 ppm with normal mating indices. At 0.5 ppm (and above), F0 adult female uterus plus cervix plus vagina weights (UCVW) were increased. At 0.5 ppm: prolonged gestational length; increased F1 stillbirth index; reduced live birth index and litter size; decreased testes and epididymides weights at weaning; unaffected AGD on pnd 0 and 21; delayed PPS; increased undescended testes; unaffected prostate weight; accelerated VP; enlarged vaginas; fluid-filled uteri. At 0.05 ppm: no F0 reproductive effects, increased F1 weanling UCVW; delayed PPS. The NOEL was 0.005 ppm (1 μg/kg/day).     

Two-Generation Reproductive Toxicity Study of Dietary Tributyl Phosphate in CD Rats

Tributyl phosphate (TBP) was tested for reproductive toxicityin rats. Thirty weanlings/sex (F0) were exposed to TBP in thediet ad libitum at 0, 200, 700, or 3000 ppm for 10 weeks andthen randomly mated within groups for 3 weeks with continuedexposure. F0 parents and 10 F1 weanlings/sex/dose were necropsied,and adult reproductive organs, urinary bladders (both sexes),kidneys (males), and livers (females) were evaluated histologically.Thirty F1 weanlings/sex/dose continued exposure for 11 weeksand were bred as described above. F1 parents and P2 weanlings,10/sex/dose, were then necropsied as described above. Adulttoxicity was observed in both sexes and generations at 700 and3000 ppm; observations included reduced body weights, weightgain and feed consumption, urinary bladder epithelial hyperplasia(both sexes), renal pelvis epithelial hyperplasia only at 3000ppm (male kidneys), and centrilobular hypertrophy (female livers).At 200 ppm, transient reductions in body weight were observedin F0 and F1 females, with urinary bladder epithelial hyperplasiain F0 males and females and in F1 males. There was no evidenceof reproductive toxicity, of reproductive organ pathology, orof effects on gestation or lactation at any dose tested. Postnataltoxicity was evidenced by consistent reductions in F1 and F2pup body weights at 3000 ppm and by occasional weight reductionsin F2 litters at 700 ppm, and was associated with maternal toxicityobserved at these doses and times. Under the conditions of thisstudy, a NOAEL was not determined for adult toxicity; the NOAELfor reproductive toxicity was at least 3000 ppm and the NOAELfor postnatal toxicity was approximately 200 ppm.     

Reproductive toxicity of MCPA (4-chloro-2-methylphenoxyacetic acid) in the rat

The reproductive effects of the administration of 4-chloro-2-methylphenoxyacetic acid (MCPA) to rats were evaluated through two generations, from prior to mating, throughout mating, to gestation and lactation. MCPA was administered in the diet at doses of 0, 50, 150, or 450 ppm to 25 male and female immature rats (F0 parents) for 10 weeks. F0 parents were then mated to produce a first litter (F1a), retained only until weaning, and were subsequently remated to produce a second litter, F1b. Groups of male and female F1b animals were then dosed as were their parents for 10 weeks postweaning, and the breeding was repeated to produce F2a and F2b animals. The study concluded with the F2b weanlings. MCPA was administered continuously throughout the study. Only minimal, non-treatment-related observations were noted, which included rhinorrhea (in both treated and control animals in the F0 generation) and malocclusion and alopecia (in both the F0 and F1b generations). There were no consistent dose-related effects on reproductive function for parental animals of either sex in either generation. Statistically significant differences were noted in body weights and body weight gains in the 450-ppm dose group for both male and female pups in F2a and F2b. There were no treatment-related macroscopic or microscopic observations noted for any animal in this study. The no-observable-effect level (NOEL) for reproductive function in rats administered MCPA continuously for two successive generations was determined to be 450 ppm (approximately 22 mg/kg/day). The NOEL for general systemic toxicity, based on body weight effects in adult animals in the F1b generation was 150 ppm. The NOEL for effects on the offspring of the F1b generation, manifested as reduced pup weights and pup weight gains was also 150 ppm (approximately 8 mg/kg/day). Based upon the results of this study, MCPA, administered for two generations to Crl:CD(SD)BR Albino rats, is considered not to be a reproductive toxicant.     

Two-generation reproductive toxicity study of inhaled acrylonitrile vapors in Crl:CD(SD) rats

To assess the effects of acrylonitrile (AN) exposure on reproduction, Sprague-Dawley rats (25/sex/group) were exposed to vapor atmospheres of AN via whole-body inhalation at concentrations of 0, 5, 15, 45 (two offspring generations) and 90 ppm (one offspring generation), 6 h daily, 1 litter/generation, through F2 weanlings on postnatal day 28. After approximately 3 weeks of direct exposure following weaning, exposure of the F1 animals at 90 ppm was terminated due to excessive systemic toxicity in the males. There were no exposure-related mortalities in adult animals, no functional effects on reproduction or effects on reproductive organs, and no evidence of cumulative toxicity or of enhanced toxicity in pregnant and lactating dams or in developing animals. Adult systemic toxicity was limited to body weight and/or food consumption deficits in both sexes and generations (greater in males) at 45 and 90 ppm and increased liver weights in the 90 ppm F0 males and females and 45 ppm F1 males. Neonatal toxicity was expressed by F1 offspring weight decrements at 90 ppm. Clinical signs of local irritation during and immediately following exposure were observed at 90 ppm. Microscopic lesions of the rostral nasal epithelium, representing local site-of-contact irritation, were observed in some animals at 5 to 45 ppm. The no-observed-adverse-effect level (NOAEL) for reproductive toxicity over two generations and neonatal toxicity of AN administered to rats via whole-body inhalation was 45 ppm. The NOAEL for reproduction was 90 ppm for the first generation. The NOAEL for parental systemic toxicity was 15 ppm.     

Reproductive toxicity evaluation of dietary butyl benzyl phthalate (BBP) in rats

Butyl benzyl phthalate (BBP) was administered in the diet at 0, 750, 3750, and 11,250 ppm ad libitum to 30 rats per sex per dose for two offspring generations, one litter/breeding pair/generation, through weaning of F2 litters. Adult F0 systemic toxicity and adult F1 systemic and reproductive toxicity were present at 11,250 ppm (750 mg/kg per day). At 11,250 ppm, there were reduced F1 and F2 male anogenital distance (AGD) and body weights/litter during lactation, delayed acquisition of puberty in F1 males and females, retention of nipples and areolae in F1 and F2 males, and male reproductive system malformations. At 3750 ppm (250 mg/kg per day), only reduced F1 and F2 offspring male AGD was present. There were no effects on parents or offspring at 750 ppm (50 mg/kg per day). The F1 parental systemic and reproductive toxicity no observable adverse effect level (NOAEL) was 3750 ppm. The offspring toxicity NOAEL was 3750 ppm. The offspring toxicity no observable effect level (NOEL) was 750 ppm, based on the presence of reduced AGD in F1 and F2 males at birth at 3750 ppm, but no effects on reproductive development, structures, or functions.     

Three-generation reproductive toxicity study of dietary bisphenol A in CD Sprague-Dawley rats.

Bisphenol A (BPA) was evaluated at concentrations of 0, 0.015, 0.3, 4.5, 75, 750, and 7500 ppm ( approximately 0.001, 0.02, 0.3, 5, 50, and 500 mg/kg/day of BPA) administered in the diet ad libitum to 30 CD((R)) Sprague-Dawley rats/sex/dose for 3 offspring generations, 1 litter/generation, through F3 adults. Adult systemic toxicity at 750 and 7500 ppm in all generations included: reduced body weights and body weight gains, reduced absolute and increased relative weanling and adult organ weights (liver, kidneys, adrenals, spleen, pituitary, and brain), and female slight/mild renal and hepatic pathology at 7500 ppm. Reproductive organ histopathology and function were unaffected. Ovarian weights as well as total pups and live pups/litter on postnatal day (PND) 0 were decreased at 7500 ppm, which exceeded the adult maximum tolerated dose (MTD). Mating, fertility, gestational indices; ovarian primordial follicle counts; estrous cyclicity; precoital interval; gestational length; offspring sex ratios; postnatal survival; nipple/areolae retention in preweanling males; epididymal sperm number, motility, morphology; daily sperm production (DSP), and efficiency of DSP were all unaffected. At 7500 ppm, vaginal patency (VP) and preputial separation (PPS) were delayed in F1, F2, and F3 offspring, associated with reduced body weights. Anogenital distance (AGD) on PND 0 was unaffected for F2 and F3 males and F3 females (F2 female AGD was increased at some doses, not at 7500 ppm, and was considered not biologically or toxicologically relevant). Adult systemic no observed adverse effect level (NOAEL) = 75 ppm (5 mg/kg/day); reproductive and postnatal NOAELs = 750 ppm (50 mg/kg/day). There were no treatment-related effects in the low-dose region (0.001-5 mg/kg/day) on any parameters and no evidence of nonmonotonic dose-response curves across generations for either sex. BPA should not be considered a selective reproductive toxicant, based on the results of this study.     

Two-generation reproductive toxicity study of inhaled toluene diisocyanate vapor in CD rats.

Twenty-eight 42-day-old pups/sex/group (F0) were exposed to toluene diisocyanate vapor (TDI; 80% 2,4-TDI, 20% 2,6-TDI) by inhalation at 0.0, 0.02, 0.08, or 0.3 ppm, 6 h/day, 5 days/week, for 10 weeks, then mated within groups for 3 weeks, with exposure 7 days/week during mating, gestation, and lactation. F0 maternal animals were not exposed from gestational day (gd) 20 through postnatal day (pnd) 4; maternal exposures resumed on pnd 5. Twenty-eight weanlings/sex/group continued exposure for 12 weeks (starting on pnd 28) and were bred as described above. F0 and F1 parents and ten F1 and F2 weanlings/sex/group were necropsied, and adult reproductive organs, pituitary, liver, kidneys, and upper respiratory tract (target organs) were evaluated histologically in ten/sex/group. Adult toxicity was observed in both sexes and generations at 0.08 and 0.3 ppm, including occasional reductions in body weights and weight gain, clinical signs of toxicity at 0.08 and 0.3 ppm, and histologic changes in the nasal cavities at 0.02, 0.08, and 0.3 ppm (including rhinitis, a nonspecific response to an irritating vapor, at all concentrations). There was no reproductive toxicity, reproductive organ pathology, or effect on gestation or lactation at any exposure concentration. Postnatal toxicity and reduced body weights and weight gains during lactation occurred only in F2 litters at 0.08 and 0.3 ppm. Therefore, under the conditions of this study, a no observed adverse effect level (NOAEL) was not determined for adult toxicity; the NOAEL for reproductive toxicity was at least 0.3 ppm, and the NOAEL for postnatal toxicity was 0.02 ppm.     

Oral (drinking water) two-generation reproductive toxicity study of bromodichloromethane (BDCM) in rats

Bromodichloromethane (BDCM) was tested for reproductive toxicity in a two-generation study in CRL SD rats. Thirty rats/sex/ group/generation were continuously provided BDCM in drinking water at 0 (control carrier, reverse osmosis membrane-processed water), 50,150, and 450 ppm (0, 4.1 to 12.6, 11.6 to 40.2, and 29.5 to 109.0 mg/kg/day, respectively). Adult human intake approximates 0.8 microg/kg/day (0.0008 mg/kg/day). P and F1 rats were observed for general toxicity (viability, clinical signs, water and feed consumption, body weights, organ weights [also three weanling Fl and F2 pups/sex/litter], histopathology [10/sex, 0- and 450-ppm exposure groups]) and reproduction (mating, fertility, abortions, premature deliveries, durations of gestation, litter sizes, sex ratios, viabilities, maternal behaviors, reproductive organ weights [also three weanling Fl and F2 pups/sex/ litter], sperm parameters, and implantations. F1 rats were evaluated for age at vaginal patency or preputial separation. Ten P and F1 rats/sex from the 0- and 450-ppm exposure groups and rats at 50 and 150 ppm with reduced fertility were evaluated for histopathology (gross lesions, testes, intact epididymis, all F1 dams for number of primordial follicles). Developmental parameters in offspring included implantation and pup numbers, sexes, viabilities, body weights, gross external alterations, and reproductive parameters (Fl adults). Toxicologically important, statistically significant effects at 150 and/or 450 ppm included mortality and clinical signs associated with reduced absolute and relative water consumption, reduced body weights and weight gains, and reduced absolute and relative feed consumption (P and F1 rats). Significantly reduced body weights at 150 and 450 ppm were associated with reduced organ weights and increased organ weight ratios (% body and/or brain weight). Histopathology did not identify abnormalities. Small delays in sexual maturation (preputial separation, vaginal patency) and more Fl rats with prolonged diestrus were also attributable to severely reduced pup body weights. Mating, fertility, sperm parameters, and primordial ovarian follicular counts were unaffected. The no-observable-adverse-effect level (NOAEL) and the reproductive and developmental NOAELs for BDCM were at least 50 ppm (4.1 to 12.6 mg/kg/day), 5125 to 15,750 times the human adult exposure level, if delayed sexual maturational associated with severely reduced body weights is considered reproductive toxicity. If considered general toxicity, reproductive and developmental NOAELs for BDCM are greater than 450 ppm (29.5 to 109.0 mg/kg/day), or 36,875 to 136,250 times the human adult exposure level. Regardless, these data indicate that BDCM should not be identified as a risk to human reproductive performance or development of human conceptuses.     

Oral (drinking water) two-generation reproductive toxicity study of dibromoacetic acid (DBA) in rats

In a two-generation study of dibromoacetic acid (DBA), Crl SD rats (30 rats/sex/group/generation) were provided DBA in drinking water at 0 (reverse osmosis-deionized water), 50, 250, and 650 ppm (0, 4.4 to 11.6, 22.4 to 55.6, and 52.4 to 132.0 mg/kg/day, respectively; human intake approximates 0.1 microg/kg/day [0.0001 mg/kg/day]). Observations included viability, clinical signs, water and feed consumption, body and organ weights, histopathology, and reproductive parameters (mating, fertility, abortions, premature deliveries, durations of gestation, litter sizes, sex ratios and viabilities, maternal behaviors, reproductive organ weights, sperm parameters and implantation sites, sexual maturation). Histopathological evaluations were performed on at least 10 P and F1 rats/sex at 0 and 650 ppm (gross lesions, testes, intact epididymis; 10 F1 dams at 0, 250, and 650 ppm for primordial follicles). Developmental observations included implantations, pup numbers, sexes, viabilities, body weights, morphology, and reproductive performance. At 50 ppm and higher, both sexes and generations had increased absolute and relative liver and kidneys weights, and female rats in both generations had reduced absolute and relative adrenal weights; adrenal changes were probably associated with physiological changes in water balance. The livers and kidneys (10/sex/group/generation) had no histopathological changes. Other minimal effects at 50 ppm were reduced water consumption and a transient reduction in body weight. At 250 and 650 ppm, DBA reduced parental water consumption, body weight gains, body weights, feed consumption, and pup body weights. P and F1 generation male rats at 250 and 650 ppm had altered sperm production (retained step 19 spermatids in stages IX and X tubules sometimes associated with residual bodies) and some epididymal tubule changes (increased amounts of exfoliated spermatogenic cells/residual bodies in epididymal tubules, atrophy, and hypospermia), although inconsistently and at much lower incidences. Unilateral abnormalities of the epididymis (small or absent epididymis) at 650 ppm in four F1 generation male rats were considered reproductive tract malformations. The no-observable-adverse-effect level (NOAEL) and reproductive and developmental NOAELs for DBA were at least 50 ppm (4.5 to 11.6 mg/kg/day), 45,000 to 116,000 times the human adult exposure level. Reproductive and developmental effects did not occur in female rats exposed to DBA concentrations as high as 650 ppm. Based on the high multiples of human exposure required to produce effects in male rats, DBA should not be identified as a human reproductive or developmental risk.     

Effect of Inhaled Propylene Oxide on Reproductive Parameters in Fischer 344 Rats

Effect of Inhaled Propylene Oxide on Reproductive Parametersin Fischer 344 Rats. HAYES, W. C, KIRK, H. D., GUSHOW, T. S.AND YOUNG, J. T. (1988). Fundam. Appl. Toxicol 10, 82–88.Reproductive parameters in Fischer 344 rats were evaluated followinginhalation of propylene oxide (PO) for two successive generations.Thirty male and 30 female rats were exposed to 0, 30, 100, or300 ppm PO for 6 hr/day, 5 days/week for 14 weeks and then matedto produce the f, litters. After weaning, 30 randomly selectedf₁, pups/sex/group were exposed to PO for 17 weeks and subsequentlymated to produce the f₂ litters. Reproductive parameters examinedincluded fertility, litter size and neonatal growth, and survival.All adults and selected weanlings were examined for gross andhistologic lesions. Toxicity due to PO was demonstrated by decreasedbody weights of parental f_o and f₁, rats at 300 ppm. No treatment-relatedeffects on fertility (mating or conception) were observed ineither f_o or f₁ matings. Neonatal survival indices for f₁, orf₂ litters revealed no treatment-related effects. Litter sizewas decreased in the f₁, rats exposed to 100 ppm PO. However,the litter size in the 300 ppm group was comparable to the controlgroup, and no effect on litter size was shown in PO-exposedf₂ litters. Pup weights were unaffected by parental exposureto PO in either generation. Pathologic examination of adultsand weanlings revealed no changes considered due to PO. Basedon these results, it is concluded that inhalation exposure toPO at levels up to 300 ppm over two generations did not produceany adverse effects on reproductive function.     

Two-generation reproductive toxicity study of inhaled tertiary amyl methyl ether (TAME) vapor in CD rats

Under Office of Prevention, Pesticides and Toxic Substances draft guidelines, CD weanling F0 rats (30 of each gender per group) inhaled tertiary amyl methyl ether vapor at 0, 250, 1500 or 3000 ppm 5 days a week and 6 h a day for 10 weeks, with vaginal cytology evaluated for weeks 8-10. The F0 animals then produced F1 offspring, with exposure 7 days a week from mating through to lactation. During the F1 prebreed exposure period, vaginal patency, preputial separation (PPS) and vaginal cytology were evaluated. The F1 animals were mated, with F2 anogenital distance measured on postnatal day zero. At F2 weaning 30 of each gender per group were selected for postwean retention, with no exposures, through vaginal patency and PPS. Body weights, feed consumption and clinical signs were recorded throughout the study. Adult F0 and F1 systemic toxicity was present at 1500 and 3000 ppm. Minor adult male reproductive toxicity was present at 3000 ppm. There were no adult effects on vaginal cyclicity, estrous cycle length, mating, fertility, pregnancy, gestational length or ovarian and uterine weights. There were no treatment-related gross or histopathologic findings in parental male or female systemic or reproductive organs. The F1 and F2 offspring toxicity was present at 1500 and 3000 ppm. The no-observable-adverse-effect level for adult systemic and offspring toxicity was 250 ppm and 1500 ppm for male reproductive toxicity (females at >3000 ppm).     

Multigenerational reproductive study of genistein (Cas No. 446-72-0) in Sprague-Dawley rats (feed study)

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. Consumption of soy and genistein has been associated with a variety of beneficial effects in animals and humans, but concerns have also been raised concerning potential adverse effects of genistein, particularly with regard to reproductive toxicity and the induction or potentiation of carcinogenesis, due primarily to its weak estrogenic activity. Because of these concerns, genistein was selected as one of the compounds to be examined in a protocol utilizing Sprague-Dawley rats to evaluate the effects of multigenerational and long-term exposures to doses of estrogenic agents that produce subtle reproductive tract lesions in developmentally exposed Sprague-Dawley rat pups. Results from the multigenerational reproductive toxicology feed study are reported in this report, and results of the 2-year feed study are reported separately (NTP, 2008a). Data from a preliminary reproductive dose range-finding feed study (NTP, 2007) that utilized exposure concentrations of up to 1,250 ppm genistein were used to select dietary exposure concentrations of 0, 5, 100, and 500 ppm for the current study. These dietary doses resulted in ingested genistein doses of approximately 0, 0.3, 7, or 35 mg genistein/kg body weight per day for males and 0, 0.5, 10, or 51 mg/kg per day for females during the time that the rats were directly consuming dosed feed. The current study was a multigenerational study (F(0) through F(4), with F(5) litters terminated at weaning) focused on reproductive endpoints. Animals were continuously exposed to genistein from the time that the F(0) generation was 6 weeks old through weaning of the F(3) generation, and animals of the F(0) through F(4) generations were sacrificed and necropsied on postnatal day 140 (PND 140). Dosed feed was removed from the F(3) pups at the time of weaning, and this generation and subsequent generations were maintained on control feed for the remainder of the study. For this study, 140 animals of each sex were obtained from the NCTR CD (Sprague-Dawley) rat colony at weaning and placed on a soy- and alfalfa-free diet that was used throughout the study in an attempt to maintain consistently low background exposure to phytoestrogens. Thirty-five animals per sex were assigned to exposure groups by a weight-ranked randomization procedure prior to the start of dietary exposure of the parental (F(0)) generation at 6 weeks of age. At the time of mating, males were paired with females from the same exposure group, and they were housed together until evidence of successful mating was detected or for a maximum of 14 days. Litters were randomly standardized to four males and four females on PND 2, and 25 litters per exposure group and their associated sires and dams were randomly selected to continue on study to produce the next generation and then necropsied at termination at 20 weeks of age (PND 140). Similar procedures were used to produce each generation. Results of the current study are summarized below. In the postweaning period, exposure to 500 ppm genistein reduced body weights predominantly in females of generations in which rats were ingesting the compound throughout adulthood (F(0) through F(2)). In the unexposed F(4) generation, female body weight was also depressed, although to a lesser extent than in the earlier generations. In the F(1) generation, postweaning body weights were reduced in all 100 and 500 ppm groups, with a more pronounced effect in the females. While pup birth weights were not significantly affected by genistein in the F(1) through F(4) generations (with the exception of 100 ppm males in the F(1) generation), both sexes showed depressed body weight gains during the preweaning period in the 500 ppm groups in all of these generations. Male pup preweaning body weight gains were also depressed in the 5 and 100 ppm groups in the F(1) generation. In the unexposed F(5) generation, pup birth weights in all exposed groups of both sexes were significantly lower than those in the controls, although it seems likely that this is a chance observation rather than a carryover effect from exposures in earlier generations. Measures of fertility were not adversely affected by genistein except for litter size. Litter size of the 500 ppm group in the F(2) generation was significantly smaller than that in the corresponding control group. The litter sizes in the F(1), F(2), and F(3) generations showed negative exposure concentration trends. Male and female 500 ppm pups in the F(1) generation had slightly reduced anogenital distances (AGDs) relative to controls when covaried by body weight. Female pups also had reduced AGDs in the F(2) (500 ppm) and F(3) (100 ppm) generations, although the statistical significance was dependent on the analysis method applied. Females exposed to 500 ppm showed an accelerated time of vaginal opening (approximately 3 days) in the F(1) and F(2) generations, while the 5 ppm group showed an earlier time of vaginal opening (1.3 days) in the F(3) generation. Body weight at vaginal opening was lower in 500 ppm females of the F(1) through F(3) generations and in the 5 ppm females of the F(1) generation. When examined shortly after vaginal opening, estrous cycles of 500 ppm females in the F(1) and F(2) generations were significantly longer (approximately 3 days and 1 day, respectively) than those of their respective control groups. Other estrous cycle disturbances (with the exception of decreased time in diestrus for 100 ppm females in the F(4) generation) were confined to the 500 ppm group of the F(1) generation and included reduced time in proestrus and an increase in the number and percentage of aberrant cycles. When the estrous cycles of older animals were examined prior to termination, the sole significant effects were a decreased time in estrus and increased time in diestrus in 5 ppm females of the F(2) generation and an increased number of abnormal cycles in 500 ppm females of the F(3) generation. No effects of genistein on male sexual development were noted with the exception of an increased time to testicular descent in 500 ppm males of the F(3) generation. Significant organ weight effects in both sexes were largely confined to single exposed groups in single generations; no clear patterns indicating toxicity to reproductive or nonreproductive organs were observed. Exposure-related microscopic lesions were confined to males, with the mammary gland and kidney affected. Incidences of mammary gland alveolar/ductal hyperplasia were significantly increased in 500 ppm males in the F(0) through F(2) generations and in 100 ppm males in the F(1) and F(2) generations. In the F(3) generation, a significant positive linear exposure concentration trend in the incidences of mammary gland hyperplasia occurred, but no exposed group differed significantly from the controls in pairwise comparisons. The more pronounced effect of genistein on the incidences of male mammary gland hyperplasia in the continuously exposed F(1) and F(2) generations as compared to the late adolescent and adult exposures of the F(0) generation and the preweaning-only exposure of the F(3) generation indicates that both developmental and adult exposures contribute to the maintenance of this effect into adulthood. Statistically significant effects of genistein on the incidences of generally minimal to mild kidney lesions in males were confined to the continuously exposed F(1) and F(2) generations. Incidences of renal tubule mineralization were significantly increased in 100 and 500 ppm males in the F(1) and F(2) generations, and incidences of inflammation and renal tubule regeneration were significantly increased in 500 ppm males in the F(1) generation. In addition to the results reported above for animals from the main study, ancillary studies were conducted with pups derived from the current study or from animals treated under similar conditions. These results have been reported elsewhere (Appendix P) and are not presented in detail in this report. Of particular importance are the data on blood and tissue genistein concentrations obtained from adult animals in the F(1) generation (Chang et al., 2000), from dams and fetuses (Doerge et al., 2001), and from dams and nursing pups (Doerge et al., 2006). These data provide measures of the internal dose resulting from the dietary exposure concentrations used in the current study and indicate that while fetal and adult exposures to genistein were at concentrations relevant to the full range of human exposures, only very low exposures were achieved during the early neonatal period when the pups were receiving exposures exclusively from the milk. The minimal exposure to genistein during this critical developmental period must be considered in the interpretation of the data derived from the current study. In summary, although genistein did show adverse effects with dietary exposures of 100 or 500 ppm, there were no clear adverse effects on the reproductive or developmental parameters measured at genistein concentrations ranging from less than 1 ppm (control diet) to 100 ppm, a range of doses producing serum concentrations achievable from the phytoestrogen content of human diets. There were few clear, overtly toxic effects that carried over across directly exposed generations or appeared to be imprinted to carry over into unexposed descendents under the conditions of exposure in this study. (ABSTRACT TRUNCATED).     

Reproductive Toxicity Evaluation of Methylethyl Ketoxime by Gavage in CD Rats

Methylethyl ketoxime (CAS No. 96-29-7; MEKO; 2-butanone oxime),an antioxidant agent used in paints, resins, and adhesives,was tested for reproductive toxicity in a two-generation studywith CD (Sprague-Dawley) rats. Thirty-eight-week-old rats/sex/group(F0) were administered MEKO in water, by gavage, at 0, 10, 100,or 200 mg/kg/day (at a dosing volume of 2 ml/kg), 5 days/weekfor 10 weeks with vaginal cytology evaluation (VCE) of F0 femalesduring the last 3 weeks of the prebreed period. Animals weremated within groups for 3 weeks with dosing during mating, gestation,and lactation for 7 days/week. F0 parents and F1 weanlings,10/sex/dose, were necropsied (after a 2-week postwean VCE inF0 females) with hematologic evaluation (including methemoglobin)and histology of adult livers, spleens, and reproductive organs.F1 weanlings, 30/sex/dose, were dosed for 11 weeks and matedas described above. Because of poor reproductive performance,not treatment related, F1 animals with no F2a litters were rebredto produce F2b litters. F1 parents and F2a weanlings, 10/sex/dose,were necropsied and evaluated as described above. Inguinal mammaryglands were examined histologically from all nonselected F1and F2 (a and b) female weanlings. Adult toxicity was observedin both generations and both sexes at all doses. Treatment-relatedparental deaths occurred at 200 mg/kg/day. At 100 and 200 mg/kg/day,parents exhibited dose-related reduced body weights and weightgains, reduced feed consumption, clinical signs of toxicity,and anemia with concomitant extramedul-lary hematopoiesis andhemosiderosis in livers and spleens (and increased spleen weights).At 10 mg/kg/day, only adult liver and spleen histologic effectswere present. There was no evidence of reproductive organ ormammary gland pathology or of reproductive or postnatal toxicityat any dose tested. There was no adult "no observable adverseeffect level" (NOAEL) established; the NOAEL for reproductiveand postnatal toxicity was at least 200 mg/kg/day for rats inthis study.     

Three-generation reproduction study of rats receiving acrylonitrile in drinking water

Acrylonitrile, a high volume organic chemical, was tested for reproductive effects in a three generation drinking water study with two matings per generation. Sprague-Dawley rats were exposed to acrylonitrile in drinking water at 0, 100, or 500 ppm. This corresponds to 0, 11+/-5 and 37+/-10 mg/kg, respectively, for males and 0, 20+/-3 and 40+/-8 mg/kg per day for the females, respectively. Water consumption was reduced in F0 rats in the 100 and 500 ppm groups. At 500 ppm, acrylonitrile reduced body weight gain and food intake of the first generation parental rats (F0). These parameters were not investigated at subsequent generations. The pup survival (both viability and lactation indices) was reduced at the 500 ppm treatment level in both matings of all three generations. Fostering the 500 ppm pups onto untreated mothers following the second mating lessened mortality, suggesting a maternal effect consistent with decreased water consumption. There was no remarkable change in the reproductive capacity in any of matings in rats at the 100 ppm concentration. In contrast, in all three generations, the body weights of the pups of the 500 ppm treatment level were reduced on Day 21 at both matings. No adverse findings were observed in the tissues of a limited number of third generation weanlings (F3b) upon gross and microscopic evaluation. No effect on the sciatic nerve was evident among the adult female rats held for 20 weeks after weaning of the second litter. There was a dose-related effect of acrylonitrile on gross masses in female rats at each parental generation held 20 weeks after the weaning of the second litter. Histopathological evaluation of these dams showed an increase in astrocytomas and zymbal gland tumors.     

Toxicology and carcinogenesis studies of divinylbenzene-HP (Cas No. 1321-74-0) in F344/N rats and B6C3F1 mice (inhalation studies)

Divinylbenzene-HP is used for producing vinyl polymers. Divinylbenzene-HP was nominated for study by the National Cancer Institute because of the potential for worker exposure and the structural similarity of divinylbenzene to styrene, a potential human carcinogen. Male and female F344/N rats and B6C3F1 mice were exposed to divinylbenzene-HP (80%) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study. Significant decreases in mean body weights occurred in both male and female rats in the 400 ppm groups. Relative kidney weights of 50 ppm or greater males and relative liver weights of 200 and 400 ppm males were significantly greater than those of the chamber controls. A clear serous nasal/eye discharge was observed in groups of males exposed to 100 ppm or greater and females exposed to 50 ppm or greater. Minimal or mild rhinitis occurred in 400 ppm rats of both sexes. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. All 400 ppm males and females died on or before the second day of the study, and two male and two female 200 ppm mice died early. Mean body weights of 100 and 200 ppm males were significantly less than those of the chamber controls. Thymus weights of exposed groups of males were significantly less than those of the chamber controls, and relative liver weights of 100 and 200 ppm males were significantly increased. Kidney and liver weights of exposed groups of females were significantly greater than those of the chamber controls. Mice exposed to 200 and 400 ppm had liver lesions including degeneration, necrosis, hemorrhage or cytomegaly. Renal tubule necrosis and regeneration occurred at 200 ppm. Necrosis or metaplasia of nasal epithelium and glands occurred in the nose in all exposure groups. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to divinylbenzene-HP at concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. There were no biologically significant changes in body weight in either sex. Nasal/eye discharge was noted in 400 ppm males and 100 ppm females. Kidney and liver weights of exposed groups of males and of 400 ppm females were generally greater than those of the chamber controls. In addition, the relative weights of the heart and testis were significantly increased in 200 and 400 ppm males. Incidences of degeneration of the olfactory epithelium in 200 and 400 ppm rats and basal cell hyperplasia of the olfactory epithelium in rats exposed to 100 ppm or greater were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to divinylbenzene-HP at concentrations of 0, 12.5, 25, 50, 100, or 200 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All 200 ppm males and nine 200 ppm females died early. Final mean body weights were significantly lower in males and females exposed to 25, 50, or 100 ppm when compared with chamber controls. Lethargy or hypoactivity was observed in the higher exposure concentration groups. Exposure to divinylbenzene was associated with necrosis of the liver and kidney in 200 ppm males and females dying early. In all exposed groups of male and female mice, there was necrosis of nasal cavity lateral walls, olfactory epithelium, and glands with resultant atrophy of olfactory epithelium and glands in females. A lower number of animals had necrotic or degenerative changes of the upper respiratory tract. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to divinylbenzene-HP at concentrations of 0, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of 400 ppm females was significantly less than that of the chamber control group. Survival of all exposed groups of males was similar to that of the chamber control group. Mean body weights of 400 ppm males and females were significantly less than those of the controls during the second half of the study. Renal tubule carcinomas occurred in two of 50 males exposed to 400 ppm in the original kidney sections, an incidence that exceeded the historical control range. In 400 ppm males, the incidence of renal tubule hyperplasia was increased, and the incidence of nephropathy was significantly increased. Following combined analysis of single and step-section data, the incidences of renal tubule adenoma and adenoma or carcinoma (combined) were marginally higher in 200 and 400 ppm males, and the incidence of renal tubule hyperplasia was significantly increased in 400 ppm males. The incidences of malignant glial cell tumors (malignant astrocytoma and oligodendroglioma) in the brain were slightly increased in 100 and 200 ppm males, and the incidence in the 200 ppm group exceeded the historical range for chamber controls. There were increased incidences of degenerative and regenerative changes in the olfactory epithelium in the nose of all exposed groups of rats. The incidence of focal chronic inflammation in the lung of 400 ppm males was significantly greater than in the chamber control group. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to divinylbenzene-HP at concentrations of 0, 10, 30, or 100 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of all exposed groups of male and female mice was similar to that of the chamber controls. Mean body weights were lower relative to chamber controls in 100 ppm males and in 30 and 100 ppm females. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in 100 ppm males were greater than chamber control incidences, but the incidences of adenoma or carcinoma (combined) were within the historical control range. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in all exposed groups of females were generally greater than those of the chamber controls; the incidences were at the upper end or exceeded the historical control ranges. There was a greater incidence and severity of alveolar epithelial hyperplasia in 100 ppm females and a greater severity of this lesion in 30 ppm females, when compared to chamber controls. The incidences and/or severities of atypical bronchiole hyperplasia were significantly increased in all exposed groups of mice. Nonneoplastic nasal lesions occurred in most exposed mice. GENETIC TOXICOLOGY: Divinylbenzene-HP was not mutagenic in any of three independent gene mutation assays using Salmonella typhimurium strains TA97, TA98, TA100, TA1535, or TA1537 or Escherichia coli tester strain WP2 uvrA with or without induced hamster or rat liver enzymes. No increases in the frequencies of micronucleated normochromatic erythrocytes or alterations in the percentages of polychromatic erythrocytes were seen in peripheral blood of male or female B6C3F1 mice exposed to divinylbenzene-HP by inhalation for 3 months. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was equivocal evidence of carcinogenic activity of divinylbenzene-HP in male F344/N rats based upon the occurrence of carcinomas in the kidney and glial tumors in the brain. There was no evidence of carcinogenic activity in female F344/N rats exposed to 100, 200, or 400 ppm divinylbenzene-HP. There was no evidence of carcinogenic activity in male B6C3F1 mice exposed to 10, 30, or 100 ppm divinylbenzene-HP. There was equivocal evidence of carcinogenic activity of divinylbenzene-HP in female B6C3F1 mice based on the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in the lung. Exposure to divinylbenzene-HP caused nonneoplastic lesions of the nasal cavity in male and female rats and of the lung and nasal cavity in male and female mice.     

Subchronic inhalation toxicity and reproductive assessment in rats of three chlorinated propenes.

Groups of 15 male and 15 female Sprague-Dawley rats were exposed to 1 of 3 chloropropene (2,3-Di = DCP; 1,2,3-Tri = TRCP; and 1,1,2,3-Tetra = TECP) vapors to provide information on repeated exposures and the potential for reproductive impairment by the most likely route of occupational exposure. Target exposure concentrations were 0, 1, 5, and 15 ppm, 6 h/d, 5 d/wk for 13 wk. The following parameters were evaluated: pharmacotoxic signs, survival, body weights, hematology, clinical blood chemistry, urine analysis, gross and histopathology (over 40 tissues/rat), organ weights, and selected weight ratios. Signs of nasal irritation were noted in rats exposed to 15 ppm of either DCP or TRCP but not TECP. Small decreases in overall body weight were observed in female rats exposed to 15 ppm TCP. An increase (approximately 15%) in spleen weight, with no corresponding histopathological or clinical findings, was observed in 15 ppm DCP-treated male rats. No other effects considered related to treatment were observed following exposure to any of the three chlorinated propenes. Additional groups of 10 male and 20 female Sprague-Dawley rats were exposed to DCP, TRCP, or TECP vapors at target concentrations of 0, 1, or 5 ppm for 6 h/d, 5 d/wk for a 10-wk premating period, a mating period, and the first 14 d (females only) of gestation. Females were allowed to deliver litters and the offspring were evaluated during a 21-d lactation period. Mating, pregnancy, and fertility indices were generally comparable among all test groups, although female mating and pregnancy indices of both DCP-treated females were lower than expected in the regular and postrecovery reproduction phase. No effects were seen on pup survival, sex distribution, body weights, organ weights, and ratios. A modest reduction in pup body weights was observed following TECP exposure but was attributed to large litter size. No treatment-related effects were seen following necropsy of adults or weanlings, nor were such effects noted following microscopic evaluation of gonads from parental animals.     

Rat two-generation reproduction and dominant lethal study of acrylamide in drinking water

Fischer 344 (F344) F(0) weanling rats, 30/sex/group, were exposed to acrylamide in drinking water at 0.0, 0.5, 2.0, or 5.0 mg/kg/day for 10 weeks and then mated. Exposure of F(0) females continued through gestation and lactation of F(1) litters. F(0) males, after F(0) mating, were removed from exposure and mated (one male: two untreated females) for the dominant lethal (DL) assay. Thirty F(l) weanlings/sex/group were exposed for 11 weeks to the same dose levels as their parents, and then mated to produce F(2) offspring. F(0) and F(l) parents and F(1) and F(2) weanlings were necropsied. Prebreeding exposure of F(0) and F(l) animals resulted in systemic toxicity at 2.0 to 5.0 mg/kg/day, with head tilt and/or foot splay increased at 0.5 to 5.0 mg/kg/day. F(0) and F(l) reproductive indices and gestational length were unaffected. Implantations and live pups/litter at birth were reduced at 5.0 mg/kg/day. Survival of F(l) and F(2) pups was reduced at 5.0 mg/kg/day for PND 0 through 4 only. In the DL assay, total and live implants were reduced, pre- and postimplantation loss was increased, and the frequency of DL factors (F(L)%) was increased at 5.0 mg/kg/day. At 5.0 mg/kg/day, adult F(l) male peripheral nerves exhibited axonal fragmentation and/or swelling; F(l) female spinal cord sections were unremarkable. The NOEL for prenatal DL was 2.0 mg/kg/day; the NOEL for adult systemic toxicity, including neurotoxicity, was < or = 0.5 mg/kg/day. Therefore, neurotoxicity and DL were differentially affected.     

Toxicology and carcinogenesis studies of genistein (Cas No. 446-72-0) in Sprague-Dawley rats (feed study)

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. Consumption of soy and genistein has been associated with a variety of beneficial effects in animals and humans, but concerns have also been raised regarding potential adverse effects of genistein, particularly with regard to reproductive toxicity and the induction or potentiation of carcinogenesis, due primarily to its weak estrogenic activity. Because of these concerns, genistein was selected as one of the compounds to be examined using a protocol designed to evaluate the effects of multigenerational and long-term exposures to doses of estrogenic agents that produce subtle reproductive tract lesions in developmentally exposed Sprague-Dawley rat pups. Results from the 2-year study are reported here, and results from the multigenerational reproductive toxicology feed study are reported separately (NTP, 2008a). Data from a preliminary dose range-finding feed study (NTP, 2007) that utilized exposure concentrations up to 1,250 ppm genistein were used to select dietary exposure concentrations of 0, 5, 100, and 500 ppm for the current study. The multigenerational reproductive toxicology study examined F(0) through F(4) generations with F(5) litters terminated at weaning and focused on reproductive endpoints (NTP, 2008a). Animals were exposed from the time that the F(0) generation was 6 weeks old through weaning of the F(3) generation, and animals of the F(0) through F(4) generations were necropsied at 20 weeks of age. The current study was a 2-year dietary study utilizing three exposure arms: continuous exposure from conception through 2 years (designated F(1) continuous, or F(1)C), exposure from conception through 20 weeks followed by control diet to 2 years [designated F(1) truncated at postnatal day (PND) 140, or F(1)T140], and exposure from conception through weaning followed by control diet to 2 years (designated F(3) truncated at PND 21, or F(3)T21). The "F(3)" designation for the F(3)T21 arm indicates that these animals were siblings of the F(3) animals from the multigenerational reproductive toxicology study (NTP, 2008a). The F(1)C and F(1)T140 animals were also siblings but were derived from a separate breeding that was identical to the procedure used to produce the F(1) generation of the multigenerational reproductive toxicology study. The animals in this study were exposed to genistein during various phases of their lives from conception until termination at 2 years, and the ingested doses varied over the course of the study. During pregnancy, the ingested doses of the dams were approximately 0, 0.5, 9, or 45 mg/kg body weight per day. During lactation, the dams' ingested doses were 0, 0.7, 15, or 75 mg/kg per day. Supplementary studies, which are described in the multigenerational reproductive toxicology study, indicated minimal transfer of genistein to pups via the dams' milk. The mean directly ingested genistein doses during the period prior to PND 140 were approximately 0.4, 8, or 44 mg/kg per day for females and 0.4, 7, or 37 mg/kg per day for males. For the period between PND 140 and the end of the study, mean ingested doses were approximately 0.3, 5, or 29 mg/kg per day for females and 0.2, 4, or 20 mg/kg per day for males. For the current study, 50 animals per sex were initially assigned to each exposure group in each arm of the study. In control groups, histopathology data from one to four additional animals that had been assigned as sentinels but that became moribund or died early were also included in the analysis and presentation. Survival was similar in all control and exposed groups and ranged from 62% to 86% for males and 43% to 64% for females. Mean body weights of 500 ppm F(1)C females were less than those of the controls throughout the study. Mean body weights of 500 ppm F(1)T140 rats were less than those of the controls throughout the study. In females of all study arms (F(1)C, F(1)T140, and F(3)T21) an early onset of aberrant estrous cycles, suggesting early reproductive senescence, was observed in the 500 ppm groups. In the F(3)T21 arm, there were also significant effects on the onset of aberrant estrous cycles in the 5 and 100 ppm groups. Pituitary gland weights were significantly increased in females in the 500 ppm groups of the F(1)C and F(1)T140 study arms and in the 100 ppm group of the F(3)T21 arm. In F(1)C females, there was a significant positive trend in the incidences of mammary gland adenoma or adenocarcinoma (combined) regardless of whether an unmodified or natural log-transformed dose scale was used in the analysis, and the incidence in the 500 ppm group was significantly greater than that in the control group. A significant negative trend occurred in the incidences of benign mammary gland fibroadenoma in F(1)C females, and the incidence in the 500 ppm group was significantly less than that in the control group. In 5 and 100 ppm F(1)T140 females, the combined incidences of adenoma and adenocarcinoma were less than those in the control or 500 ppm groups, although these were not statistically significant differences. When the natural log-transformed dose scale was used, a marginally significant positive trend occurred in the incidences of adenoma or adenocarcinoma (combined) in F(3)T21 females. There were positive trends in the incidences of adenoma or carcinoma (combined) in the pars distalis of the pituitary gland of females in the F(1)C and F(1)T140 arms, and the incidence in the 500 ppm group was significantly greater than that in the controls in the F(1)C study arm. In F(1)C males, a significant positive trend (unmodified dose scale only) occurred in the incidences of combined adenoma or carcinoma of the pancreatic islets. While the incidence in the 500 ppm group was elevated relative to that in the control group (6/49 versus 1/49), this was not statistically significant. The fact that transitional lesions (i.e., hyperplasia) were not observed combined with variable control rates in males of this substrain of rats led to the conclusion that this lesion was not likely to be related to genistein treatment. CONCLUSIONS: Under the conditions of this 2-year feed study with continuous exposure to the test compound from conception through termination (F(1)C), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was some evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on increased incidences of mammary gland adenoma or adenocarcinoma (combined) and pituitary gland neoplasms. The incidence of benign mammary gland fibroadenoma in female rats was significantly decreased in the 500 ppm group. Under the conditions of this 2-year feed study with exposure to the test compound from conception through 20 weeks followed by control feed until termination (F(1)T140), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was equivocal evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on marginally increased incidences of pituitary gland neoplasms. Under the conditions of this 2-year feed study where offspring of three prior generations of animals exposed to the test compound were exposed from conception through weaning (PND 21) followed by control feed until termination (F(3)T21), there was no evidence of carcinogenic activity of genistein in male Sprague-Dawley rats exposed to 5, 100, or 500 ppm. There was equivocal evidence of carcinogenic activity of genistein in female Sprague-Dawley rats based on increased incidences of mammary gland adenoma or adenocarcinoma (combined). Exposure to genistein was also shown to accelerate the onset of aberrant estrous cycles in female Sprague-Dawley rats whether exposures were continuous or truncated at PND 140 or at weaning. The effects of genistein on estrous cycling and the incidences of common hormonally related spontaneous neoplasms of female Sprague-Dawley rats are consistent with an estrogenic mechanism of toxicity.     

Three-Generation Reproduction Study with Dioctyl Sodium Sulfosuccinate in Rats

Three-Generation Reproduction Study with Dioctyl Sodium Sulfosuccinatein Rats. MACKENZIE, K., HENWOOD, S., FOSTER, G., AKIN, F., DAViS,R., DEBAECKE, P., SISSON, G., AND MCKINNEY, G. (1990). Fundam.Appl Toxicol. 15, 53–62. Groups of 30 male and 30 femalerats (F0) were fed diets containing 0, 0. 1, 0.5, or 1.0% dioctylsodium sulfosuccinate (DSS) for 10 and 2 weeks, respectively.The F0 animals were then mated to produce an F1 litter. Groupsof 30 male and 30 female F1 animals were fed the same dose levelsfor at least 10 weeks postweaning, and the breeding programwas repeated to produce F2 animals. F3 animals were producedfrom F2 animals by the same procedure. The study was terminatedwith the F3 wean lings. Test diets were fed continuously throughoutthe study. All F0, F1, and F2 adults and F3 weanlings (one/sex/litter)were necropsied and given a macroscopic examination. There wereno effects on reproductive function for parental animals ofeither sex during any of the three generations in this study.At the highest dose level (1.0% DSS), body weights were lowerthan those of controls dunng the premating phase for males inall three generations and for F1 and F2 females. Body weightsfor F1 and F2 males and females in the 0.5% dose group werealso low during the premating phase. Pup weights on LactationDay 0 were significantly lower than those of controls only forthe high-dose group during the third generation. However, lowerpup weight gains in the mid-and high-dose groups resulted insignificantly lower pup weights on Day 21 for all three generations.Perinatal pup survival across three generations ranged from96 to 100% for the control and treated groups. Pup survivalranged from 95 to 100% for controls, from 98 to 100% for low-and mid-dose groups, and from 91 to 99% for the high-dose group.There were no treatment-related mortality and antemortem ormacroscopic observations. In summary, DSS administered in thediet to three successive generations of rats at levels of 0.5and 1.0% caused a reduction in body weights for parental malesin all generations and for F1 and F2 females, Pup weights atthe 0.5 and 1.0% dose levels were also lower than those of thecontrol in all three generations. However, the reduced bodyweights did not interfere with development of normal reproductiveperformance. DSS at levels up to 1.0% had no effects on thereproductive function of either sex in any generation and producedno treatment-related antemortem or macroscopic observations.     

Carcinogenicity and chronic toxicity of di-2-ethylhexyl terephthalate (DEHT) following a 2-year dietary exposure in Fischer 344 rats.

The carcinogenicity and chronic toxicity potential of di-2-ethylhexyl terephthalate (DEHT) was assessed in F-344 rats (50/sex/dose) by dietary exposure for 104 weeks. Exposure levels of 0, 1500, 6000 or 12,000 ppm resulted in average daily doses of 79, 324 and 666 mg/kg/day for males and 102, 418 and 901 mg/kg/day for females. Animals were observed daily for clinical signs and detailed physical examinations were performed weekly. Body weight and food consumption were measured at scheduled intervals. During weeks 103-104, urine and blood samples were collected and analyzed. Eyes were examined during week 104 using a binocular indirect ophthalmoscope. At necropsy, organs were weighed and examined macroscopically and microscopically. No histological effects were noted in any organ at any dose and there was no increase in the incidence of any tumor types. Toxic responses were confined to lower weight gains and food conversion efficiency in males and females ingesting 6000 or 12,000 ppm. The severity of a normal geriatric degenerative retinal change was exacerbated in females exposed to 6000 or 12,000 ppm and in males exposed to 12,000 ppm. Therefore, the no-observed effect level (NOEL) for tumorigenicity was 12,000 ppm and the NOEL for chronic toxicity was 1500 ppm.