Tetrahydrofuran: two-generation reproduction toxicity in Wistar rats by continuous administration in the drinking water.

In a two-generation reproduction toxicity study, 25 male and 25 female Wistar rats per dose group and generation were exposed continuously to tetrahydrofuran in the drinking water for at least 70 days prior to and during mating, gestation, parturition and lactation to weaning, at concentrations of 0, 1000, 3000 or 9000 ppm (approximately 100, 300 and 700 mg/kg/day in males and females premating, 100, 300 and 800 mg/kg/day in females during gestation, and 200, 500 and 1300 mg/kg/day in females during lactation) through two successive generations. In both generations and sexes, water consumption was dose-relatedly reduced at all doses; food consumption and body weight were reduced at 9000 ppm. Necropsy kidney weights were increased in 9000 ppm F0 males. Pup body weight gain during lactation was reduced in both generations (F1 and F2 pups) and eye opening delayed in the first generation (F1 pups) at 9000 ppm; there were no treatment-related malformations. The NOAEL of tetrahydrofuran in drinking water is 9000 ppm for parental fertility and reproductive performance, and 3000 ppm for systemic parental and developmental toxicity.     

Developmental and reproductive toxicity evaluation of toluene vapor in the rat. I. Reproductive toxicity

The reproductive toxicity of toluene was evaluated in a 2-generation test in which male and female Sprague–Dawley rats, parental (F0) and first generation (F1), were exposed to toluene via whole body inhalation, 6 h/day, 7 days/week for 80 days premating and 15 days of mating at concentrations of 0, 100, 500 and 2000 ppm (0, 375, 1875 and 7500 mg/m³). Toluene was administered at 2000 ppm to both sexes, or to females or males only to be mated with untreated partners. Pregnant females at all dose levels were exposed from gestation day (GD) 1–20 and lactation day (LD) 5–21. At LD5, females were removed from their litters for daily exposure and returned when 6 h of exposure was completed. F1 pups selected to produce the F2 generation were treated for 80 days beginning immediately after weaning (LD21) and initially mated at a minimum of 100 days of age. F2 pups were not exposed to toluene by inhalation.

Toluene exposure did not induce adverse effects on fertility, reproductive performance, or maternal/pup behaviors during the lactation period in males and females of the parental or first generation, but did inhibit growth in F1 and F2 offspring in the 2000 ppm (both sexes treated) and 2000 ppm (females only treated) groups. Caesarean section of selected 2000 ppm (both sexes treated) dams at GD20 showed reduced fetal body weight and skeletal variations. Exposure to toluene caused decreased pup weights throughout lactation in F1 and F2 2000 ppm (both sexes treated), and 2000 ppm (females only treated) groups. Exposure at 2000 ppm to male parents only did not induce similar weight inhibition in offspring. The toluene offspring NOAEL is 500 ppm in groups in which maternal animals were exposed, and 2000 ppm for male only treated groups.     

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic reformed naphtha distillate in rats

A distillate of light catalytic reformed naphtha (CAS number 64741-63-5, LCRN-D) administered by inhalation was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening protocol. LCRN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 6 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for approximately 7 consecutive weeks. Dams and litters were sacrificed on postnatal d 4 and males were sacrificed within the week after the last litter was necropsied. Parental systemic effects observed at the 7500 ppm exposure level included slightly lower body weights for males throughout the study. Increased kidney to body weight and increased liver to body weight ratio in male rats exposed to 7500 ppm LCRN-D may be related to slightly lower final mean body weights. Body and organ weight data for female rats in all exposure groups were comparable to controls. No test-material-related microscopic changes were observed in the reproductive organs or nasal turbinate tissue of either sex. Reproductive performance was unaffected by exposure to LCRN-D. The mating and fertility indices were 100% in all groups. There were no significant exposure-related differences in implantation sites or live pups per litter, and no gross abnormalities were observed in pups from treated dams. Pups born from LCRN-D-exposed dams showed comparable body weights and weight gain to control pups. The viability index on postpartum d 4 was > or =97%. Under conditions of this study, the no-observed-adverse-effect level (NOAEL) for exposure to light catalytic reformed naphtha distillate for parental effects was 2500 ppm and the NOAEL for reproductive and developmental toxicity was 7500 ppm.     

TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS: REPRODUCTIVE AND DEVELOPMENTAL EFFECTS OF LIGHT CATALYTIC REFORMED NAPHTHA DISTILLATE IN RATS

A distillate of light catalytic reformed naphtha (CAS number 64741-63-5, LCRN-D) administered by inhalation was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening protocol. LCRN-D was administered as a vapor, 6 h/d, 7 d/ wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 6 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for approximately 7 consecutive weeks. Dams and litters were sacrificed on postnatal d 4 and males were sacrificed within the week after the last litter was necropsied. Parental systemic effects observed at the 7500 ppm exposure level included slightly lower body weights for males throughout the study. Increased kidney to body weight and increased liver to body weight ratio in male rats exposed to 7500 ppm LCRN-D may be related to slightly lower final mean body weights. Body and organ weight data for female rats in all exposure groups were comparable to controls. No test-material-related microscopic changes were observed in the reproductive organs or nasal turbinate tissue of either sex. Reproductive performance was unaffected by exposure to LCRN-D. The mating and fertility indices were 100% in all groups. There were no significant exposure-related differences in implantation sites or live pups per litter, and no gross abnormalities were observed in pups from treated dams. Pups born from LCRN-D-exposed dams showed comparable body weights and weight gain to control pups. The viability index on postpartum d 4 was 97%. Under conditions of this study, the no-observed-adverse-effect level (NOAEL) for exposure to light catalytic reformed naphtha distillate for parental effects was 2500 ppm and the NOAEL for reproductive and developmental toxicity was 7500 ppm.     

Effects on reproduction in Fischer 344 rats exposed to ethylene oxide by inhalation for one generation

After 12 weeks of exposing male and female Fischer 344 rats (6 hr/day, 5 days/week) to either 100, 33, or 10 ppm of ethylene oxide vapor, these animals were mated, and the females were continued on exposure from Day 0 through Day 19 of gestation (6 hr/day, 7 days/week). The major treatment-related adverse effect was significantly fewer pups born per litter in the highest exposure level only. There were fewer implantation sites per pregnant female, and a smaller ratio of the number of fetuses born to the number of implantation sites per pregnant female in the 100-ppm exposure group than in any other group. No statistically significant differences of male or female fertility indices were noted between the ethylene oxide exposure and air-control groups. There were significantly more animals with a gestation period longer than 22 days in the 100-ppm exposure group when compared to either air-control group. No significant differences in body weight gain or any other signs of toxic effects from exposure were observed in the F0 generation. Moreover, there was no treatment-related adverse effect on survival or growth rate of the Fla generation during the lactation period, even when the dams were exposed to ethylene oxide during this period.     

Reproductive and repeated dose toxicity of cyclododecatriene (CDDT) in rats following oral (gavage) treatment

Cyclododecatriene (CDDT, CAS No. 4904-61-4) was administered daily by oral gavage to groups of Crl:CD (SD)IGS BR rats at dose levels of 0 (control), 30, 100, or 300 mg/kg/day. Female rats were dosed for four weeks premating, through mating, gestation, and lactation (a total of 55 to 63 days of treatment). Male rats were treated for 55 days (four weeks premating and through mating). Premating, body weights, food consumption, and clinical signs were recorded. Hematology, clinical chemistry, and urine analyses were conducted at the end of the premating period. A neurobehavioral test battery was conducted prior to and after four weeks of treatment. After the premating period, females were paired with males from the same groups for 1-2 weeks. Litters were delivered, pups were evaluated for structural integrity, and pup body weights were recorded on days 0 and 4 postpartum. Lactating females and their offspring were sacrificed on postpartum day 4. Selected organs were weighed and the tissues were examined microscopically from the lactating females. Offspring were examined for clinical abnormalities. A test substance-related reduction in body weight gain occurred in male rats administered 300 mg/kg/day. Decreased body weight gain in the 300 mg/kg/day males was accompanied by increased food consumption and decreased food efficiency. Females administered 100 or 300 mg/kg/day had test substance-related, significantly decreased body weight and body weight gain during gestation, that was accompanied by a significant increase in food consumption (300 mg/kg/day group only), and significantly decreased food efficiency. There were no test-substance related effects on clinical observations in males or females during the premating phase, or in females during gestation or lactation. Neurobehavioral parameters and motor activity were unaffected by CDDT-treatment. During this study, statistically significant treatment-related changes were observed in several clinical pathology parameters. The decreases in red cell mass (RBC, HGB, HCT) were minimal and, due to the magnitude, were not expected to result in biological effects. Similarly, minimally increased potassium and mildly decreased triglycerides were not of a magnitude to be biologically significant. Finally, changes in serum enzymes (AST, ALT, ALP), urea nitrogen, and serum protein occurred in directions that are not associated with toxicity. The changes in urine volume, urine concentration, and urea nitrogen may be the result of elevated glomerular filtration rate and altered tubular fluid flow, in the absence of any histopathological change. No effects on reproduction in parental males or females were produced by CDDT. Body weights of pups in the 300 mg/kg group were significantly decreased on postpartum days 0 and 4. There were no test-substance related effects on clinical observations, number of pups born, and the number of pups born alive, or the number of pups surviving through lactation day 4. The no-observed-adverse-effect level (NOAEL) for CDDT was 30 mg/kg/day based on decreased body weight and body weight gain, increased food consumption, and decreased food efficiency in females administered 100 or 300 mg/kg/day. The NOEL in pups was 100 mg/kg/day, based on decreased body weights of pups in the 300 mg/kg/day group during lactation.     

REPRODUCTIVE AND REPEATED DOSE TOXICITY OF CYCLODODECATRIENE (CDDT) IN RATS FOLLOWING ORAL (GAVAGE) TREATMENT

ABSTRACT

Cyclododecatriene (CDDT, CAS No. 4904-61-4) was administered daily by oral gavage to groups of Crl:CD®(SD)IGS BR rats at dose levels of 0 (control), 30, 100, or 300 mg/kg/day. Female rats were dosed for four weeks premating, through mating, gestation, and lactation (a total of 55 to 63 days of treatment). Male rats were treated for 55 days (four weeks premating and through mating). Premating, body weights, food consumption, and clinical signs were recorded. Hematology, clinical chemistry, and urine analyses were conducted at the end of the premating period. A neurobehavioral test battery was conducted prior to and after four weeks of treatment. After the premating period, females were paired with males from the same groups for 1–2 weeks. Litters were delivered, pups were evaluated for structural integrity, and pup body weights were recorded on days 0 and 4 postpartum. Lactating females and their offspring were sacrificed on postpartum day 4. Selected organs were weighed and the tissues were examined microscopically from the lactating females. Offspring were examined for clinical abnormalities. A test substance-related reduction in body weight gain occurred in male rats administered 300 mg/kg/day. Decreased body weight gain in the 300 mg/kg/day males was accompanied by increased food consumption and decreased food efficiency. Females administered 100 or 300 mg/kg/day had test substance-related, significantly decreased body weight and body weight gain during gestation, that was accompanied by a significant increase in food consumption (300 mg/kg/day group only), and significantly decreased food efficiency. There were no test-substance related effects on clinical observations in males or females during the premating phase, or in females during gestation or lactation. Neurobehavioral parameters and motor activity were unaffected by CDDT-treatment. During this study, statistically significant treatment-related changes were observed in several clinical pathology parameters. The decreases in red cell mass (RBC, HGB, HCT) were minimal and, due to the magnitude, were not expected to result in biological effects. Similarly, minimally increased potassium and mildly decreased triglycerides were not of a magnitude to be biologically significant. Finally, changes in serum enzymes (AST, ALT, ALP), urea nitrogen, and serum protein occurred in directions that are not associated with toxicity. The changes in urine volume, urine concentration, and urea nitrogen may be the result of elevated glomerular filtration rate and altered tubular fluid flow, in the absence of any histopathological change. No effects on reproduction in parental males or females were produced by CDDT. Body weights of pups in the 300 mg/kg group were significantly decreased on postpartum days 0 and 4. There were no test-substance related effects on clinical observations, number of pups born, and the number of pups born alive, or the number of pups surviving through lactation day 4. The no-observed-adverse-effect level (NOAEL) for CDDT was 30 mg/kg/day based on decreased body weight and body weight gain, increased food consumption, and decreased food efficiency in females administered 100 or 300 mg/kg/day. The NOEL in pups was 100 mg/kg/day, based on decreased body weights of pups in the 300 mg/kg/day group during lactation.     

Endocrinological, neurochemical, and anabolic effects of polybrominated biphenyls in male and female rats

Pregnant rats were placed on a control diet or on a diet containing 100 ppm polybrominated biphenyls (PBBs, Firemaster PB-6) on Day 8 of gestation. On Day 28 postpartum the pups were weaned onto the same diet as their mothers, and maintained on this diet until sacrificed during the ninth week. Body weight gain was reduced in both the male and female rats exposed to PBBs. The absolute weights of some organs (ventral prostate and seminal vesicles in males, and adrenal and pituitary glands in females) were reduced in animals maintained on the PBB diet, but when expressed as a percentage of body weight only the ventral prostate weight remained significantly reduced. Exposure to PBBs did not affect plasma concentrations of luteinizing hormone, prolactin, or corticosterone; nor did it affect the increase in the plasma concentration of the latter two hormones in response to a mild environmental stress. Exposure to PBBs did not alter the steady-state concentrations of norepinephrine or dopamine in the posterior pituitary or selected brain regions. Furthermore, treatment with PBBs did not alter the rates of synthesis of these catecholamines (as estimated by the rate of accumulation of dihydroxyphenylalanine following inhibition of dihydroxyphenylalanine decarboxylase) in the brains of female rats on the day of diestrus or estrus. On the basis of vaginal cytology, exposure to PBBs significantly lengthened the estrous cycle of female rats.     

Reproduction in Fischer-344 Rats Exposed to Methyl Chloride by Inhalation For Two Generations

Reproduction in Fischer-344 Rats Exposed to Methyl Chlorideby Inhalation For Two Generations. HAMM, T. E., JR., RAYNOR,T. H., PHELPS, M. C, AUMAN, C. D., ADAMS, W. T., PROCTOR, J.E., AND WOLKOWSKI-TYL, R. (1985) Fund. Appl. Toxicol. 5, 568–577.Male and female Fischer-344 rats were exposed to methyl chlorideby inhalation (0, 150, 475, or 1500 ppm, 6 hr/day, 5 days/week,40 males and 80 females per group). The only treatment-relatedclinical signs were a 10 to 20% body weight gain depression(BWGD) in both males and females exposed to 1500 ppm at allweekly weighings after 2 weeks of exposure and a 5–7%BWGD in 475-ppm exposed animals after Day 57. After 10 weeksthe exposure schedule was changed to 6 hr/day, 7 days/week andeach male was mated to two exposed females. The mating periodwas ended after 2 weeks, at which point 10 males/group werenecropsied. The only tratment-related lesions Found were severebilateral testicular degeneration (10/10) and granulomas inthe epididymis (3/10) in the 1500-ppm males. The remaining 30males per group were then removed from exposure and mated duringa 2-week period with 60 unexposed females. The exposed femaleswere continued on exposure from the start of mating to PostnatalDay 28 (6 hr/day, 7 days/week). The females were not exposedfrom Gestation Day 18 to Postnatal Day 4, and the pups werenever directly exposed prior to weaning. There were no significantdifferences between groups in the number of exposed or unexposedfemales that mated, as evidenced by copulation plugs. No litterswere born to exposed or unexposed females mated to the 1500-ppmmales. There was no significant difference in the number oflitters produced by the 150-ppm groups when compared to thecontrol groups. Fewer litters were born in the 475-ppm groupsthan in the control groups. No differences in litter size, sexratio, pup viability, or pup growth were Found among the 475-ppm,150-ppm, or control F₀ groups. When bred 10 weeks after thecessation of exposures, 5 to 20 1500-ppm F₀ males had regainedthe ability to sire normal litters. The same number of 475-ppmF₀ males proved as fertile (15/ 20) as control F₀ males (13/20).After weaning, F₁ pups from the 475-, 150-, and 0-ppm groupswere exposed to the same concentrations of methyl chloride For10 weeks and then mated. A trend toward decreased fertilitywas Found in the 475-ppm F₁ group     

Male fertility study on N,N-dimethylacetamide administered by the inhalation route to Sprague-Dawley rats

Male Sprague-Dawley rats were exposed to N,N-dimethylacetamide (DMAC) and mated to untreated virgin females. Mean analytical exposure concentrations were 40, 116, and 386 ppm, respectively. A control group was exposed to air containing no DMAC. A total of 69 d of exposure to DMAC at these levels produced treatment-related effects of increased liver weights and liver/body weight ratios in the high- and medium-exposure groups of male rats. Reproductive data indicated no treatment-related effects on copulation efficiency or efficiency in effecting pregnancy, and there were no detectable treatment-related effects on preimplantation loss, postimplantation loss, embryotoxicity, or fetotoxicity in litters of females mated to males exposed to DMAC at the levels used in this study. The significance of these findings is discussed.     

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic cracked naphtha distillate in rats

A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in high-dose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. IncreaSed kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related microscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was > or =90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was > or =97%; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.     

Behavioral and neurochemical alterations in the offspring of rats after maternal or paternal inhalation exposure to the industrial solvent 2-methoxyethanol

The industrial solvent 2-methoxyethanol (2ME) has antifertility effects in male rats at 300 ppm and is tetragenic in rats and rabbits at 50 ppm. The present research investigated if exposure of paternal or maternal animals to 25 ppm 2ME, the current U. S. permissible occupational exposure limit, would produce detectable effects in the offspring. Eighteen male young-adult Sprague-Dawley rats were exposed to 25 ppm 2ME 7 hr/day, 7 days/week for 6 weeks; they were then mated with untreated females which were allowed to deliver and rear their young. In addition, groups of 15 pregnant rats were exposed 7 hr/day on gestation days 7–13 or 14–20 and allowed to deliver and rear their young. At birth, litters were culled to 4 females and 4 males for behavioral testing of neuromotor function, activity, and simple learning ability on days 10 through 90. In addition, brains from new born and 21-day-old offspring were analyzed for neurochemical deviations from controls. No effects on paternal or maternal animals, nor on the number or weight of live offspring, were noted. Behavioral testing revealed significant differences from controls only in avoidance conditioning of offspring of mothers exposed on days 7–13. In contrast, neurochemical deviations were observed in brains from 21-day-old offspring from the paternally exposed group as well as from both maternally exposed groups; changes were numerous in the brainstem and cerebrum but were fewer in the cerebellum and midbrain. Thus it appears that both paternal and maternal inhalation of 25 ppm 2ME produces some effect which is reflected in neurochemical deviations in the offspring.     

Inhalation studies to evaluate the teratogenic and embryotoxic potential of beta-chloroprene (2-chlorobutadiene-1,3)

Pregnant rats in two studies were exposed by inhalation to 0, 1, 10, and 25 ppm of β-chloroprene for 4 hr daily. Dams in one study (50 per group) were exposed on Days 1 through 12 and sacrificed on Day 17 to evaluate the embryotoxic potential of β-chloroprene. Dams in a teratology study (25 per group) were exposed on Days 3 through 20 and sacrificed on Day 21 of gestation. Male rats in a reproduction study were exposed to 25 ppm or β-chloroprene, 4 hr daily for 22 days and bred with untreated virgin females (three new females per male each week) for 8 consecutive weeks. No maternal, embryonal, or fetal toxicity was observed in the first two studies at levels of 1, 10, or 25 ppm β-chloroprene. Maternal exposure to β-chloroprene did not affect the development of rat fetuses as measured by weight and crownrump length and did not result in major external, skeletal, or soft tissue malformations. The reproductive capability of males exposed to 25 ppm of β-chloroprene 4 hr daily for 22 days was not impaired. The results of these studies indicate that 25 ppm of β-chloroprene, the present threshold limit value, is not embryotoxic or teratogenic and does not impair reproductive capability of male rats. These results are at variance with previous findings from the Soviet Union.     

Developmental effects of inhalation exposure to 2-bromopropane in rats

2-Bromopropane (2-BP), known as a reproductive and hematopoietic toxicant in humans, was assessed for developmental toxicity. Sprague-Dawley rats were exposed by inhalation to 2-BP at a concentration of 0 (control), 125, 250, 500, or 1000 ppm for 6 h per day, 7 days per week during 2 weeks of the pre-mating period, during the mating period until copulation and during the period of gestation days 0-19. After parturition, dams were allowed to breast feed their pups until postnatal day 4. 2-BP exposure resulted in no signs of maternal toxicity as assessed by clinical observations and body weight gain. On the other hand, the inhalation exposure to 1000 ppm markedly decreased the number of pups born, although the number of implantations did not decrease. No effect of 2-BP on pups weights or survival until postnatal day 4 was found. It was found that the repeated inhalation exposure of rats to 1000 ppm 2-BP induced fetal lethality during the post-implantation period.     

Dietary methoxychlor exposure modulates splenic natural killer cell activity, antibody-forming cell response and phenotypic marker expression in F0 and F1 generations of Sprague Dawley rats

Methoxychlor, a chlorinated hydrocarbon pesticide, is a persistent environmental contaminant that has been identified in human reproductive tissues. Methoxychlor has been shown to be estrogenic in both in vivo and in vitro studies. As an endocrine disrupter, it may have the potential to adversely affect endocrine, reproductive, and immune systems in animals. The present study evaluated methoxychlor's immunotoxic potential in F0 (dams) and F1 generations of Sprague Dawley rats exposed to an isoflavone-free diet containing methoxychlor at concentrations of 10, 100, and 1000 ppm. In dams, exposure to methoxychlor from gestation day 7 to postpartum day 51 (65 days total exposure) produced a significant increase in the NK activity (1000 ppm) and the percentages of T cells (1000 ppm), helper T cells (1000 ppm) and macrophages (100 and 1000 ppm). In contrast, a decrease in the numbers of splenocytes and B cells was observed at the 100 and 1000 ppm concentrations. In F1 males, exposure to methoxychlor gestationally, lactationally and through feed from postnatal day 22-64 (78 days total exposure) produced an increase in the spleen IgM antibody-forming cell response to sheep red blood cells (100 and 1000 ppm) and the activity of NK cells (1000 ppm). However, there was a decrease in the terminal body weight (1000 ppm), spleen weight (1000 ppm), thymus weight (100 and 1000 ppm), and the numbers of splenocytes (1000 ppm), B cells (100 and 1000 ppm), cytotoxic T cells (1000 ppm) and NK cells (100 and 1000 ppm). In F1 females, exposure to methoxychlor produced a decrease in the terminal body weight (1000 ppm) and the percentages of cytotoxic T cells (10, 100 and 1000 ppm). These results demonstrate that developmental and adult dietary exposure to methoxychlor modulates immune responses in Sprague Dawley rats. Immunological changes were more pronounced in the F1 generation male rats that were exposed during gestation and postpartum, when compared to the F0 and F1 generation females. Increases in antibody-forming cell response and NK cell activity, and altered spleen cell subpopulation numbers were observed in the F1 generation male rats, without similar changes to the F1 generation females.     

TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS: REPRODUCTIVE AND DEVELOPMENTAL EFFECTS OF LIGHT CATALYTIC CRACKED NAPHTHA DISTILLATE IN RATS

A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/ Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/ d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in highdose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. Increased kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related m icroscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was 90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was 97% ; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.     

An inhalation toxicity study of chlorine in Fischer 344 rats following 30 days of exposure.

A subacute study was completed in groups of 10 male and 10 female Fischer 344 rats exposed to air (controls), 1, 3, or 9 ppm chlorine for 6 hr/day, 5 days/week, for 6 weeks. Concentration related decreases in body weight gain were seen at all exposure concentrations in females and at 3 and 9 ppm in males. Additionally, three females at 9 ppm died before the end of Day 30 of exposure. Urinalysis, hematology, and clinical chemistry evaluations were completed on the surviving animals. The urine specific gravity was elevated at all exposure concentrations in the females and at 3 and 9 ppm in the males. The hematocrit and white blood cell count were increased in the females exposed to 9 ppm. Elevations in alkaline phosphatase activity, blood urea nitrogen, γ-glutamyl transpeptidase, and serum glutamic-pyruvic transaminase occurred at 9 ppm; alkaline phosphatase was elevated at 3 ppm in rats of both sexes. Widespread evidence of inflammation was seen throughout the respiratory tract with hyperplasia and hypertrophy of epithelial cells of the respiratory bronchioles, alveolar ducts, and alveoli of male and female rats exposed to 9 ppm. Changes in male rats at 3 or 1 ppm consisted of focal inflammation of the nasal turbinates and a slight to moderate inflammatory reaction around the respiratory bronchioles and alveolar ducts. Increased eosinophilic cytoplasmic homogeneity and decreased granularity of the epithelial cells of the proximal convoluted tubules were seen in the kidneys of male rats exposed to 9 ppm. The livers of rats of both sexes at 9 or 3 ppm had an increased hepato-cellular cytoplasmic vacuolation. These data indicated that repeated exposure of Fischer 344 rats to chlorine resulted in pulmonary effects at all levels of chlorine used, and hepatic and renal effects at 9 and 3 ppm.     

Toxicology and carcinogenesis studies of alpha-methylstyrene (Cas No. 98-83-9) in F344/N rats and B6C3F1 mice (inhalation studies)

alpha-Methylstyrene is used in the production of acrylonitrile-butadiene-styrene resins and copolymers, which improve the impact and heat-resistant properties of polymers, specialty grades of plastics, rubber, and protective coatings. alpha-Methylstyrene also moderates polymerization rates and improves product clarity in coatings and resins. Low molecular weight liquid polymers are used as plasticizers in paints, waxes, adhesives, and plastics. alpha-Methylstyrene was nominated by the U.S. Environmental Protection Agency for toxicologic evaluation and genotoxicity studies based on its high production volume and limited information available on its toxicity. Male and female F344/N rats and B6C3F1 mice were exposed to alpha-methylstyrene (99.5% pure) by inhalation for 3 months or 2 years. Inhalation studies were conducted because the primary route of human exposure is via inhalation. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were exposed to the same concentrations for 23 days. All rats survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Kidney weights were significantly increased in 1,000 ppm males and 600 and 1,000 ppm females. Statistically significant increases in liver weights occurred in 150 ppm or greater males and 600 and 1,000 ppm females. The incidences of renal hyaline droplet accumulation were similar between exposed groups and chamber control groups, but the severity of hyaline droplet accumulation in 600 and 1,000 ppm males was greater than in chamber controls. Consistent with the hyaline droplet accumulation, an exposure-related increase in alpha2μ-globulin was detected in the kidneys of males exposed to alpha-methylstyrene. Morphologic changes were not detected in the liver. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Two female mice in the 1,000 ppm group died before exposure on day 3. Final mean body weights of 600 and 1,000 ppm males and 75, 300, and 1,000 ppm females were significantly less than those of the chamber controls; final mean body weight gains of mice exposed to 300 ppm or greater were also significantly less. Moderate to severe sedation (males only) and ataxia were observed in 1,000 ppm mice. The absolute liver weights of 600 and 1,000 ppm females and the relative liver weights of 300, 600, and 1,000 ppm males and females were significantly increased. The estrous cycle lengths of 600 and 1,000 ppm female mice were significantly longer than that of the chamber controls. Minimal to mild centrilobular hypertrophy was present in the livers of male and female mice exposed to 600 or 1,000 ppm alpha-methylstyrene. The incidences of exposure-related nasal lesions, including atrophy and hyperplasia of Bowman's glands and atrophy and metaplasia of the olfactory epithelium, were significantly increased in all exposed groups of males and females. The incidences of hyaline degeneration, characterized by the accumulation of eosinophilic globules in the cytoplasm of the respiratory epithelium, were significantly increased in females exposed to 150 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 1,000 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival rates of exposed male and female rats were similar to those of the chamber controls. The mean body weights of 1,000 ppm males and females were less than those of the chamber control groups during year 2 of the study. Two 1,000 ppm males and one 300 ppm male had renal tubule carcinomas, and one 300 ppm male had a renal tubule adenoma. Because of the neoplasms observed in 300 and 1,000 ppm males at the end of the 2-year study and the finding of alpha2μ-globulin accumulation in the kidneys at 3 months, which is often associated with kidney neoplasms, additional step sections of kidney were prepared; additional males with focal hyperplasia or adenoma were identified. The incidences of renal tubule adenoma and carcinoma (combined) in the 1,000 ppm males were significantly greater than those in the chamber controls when the single and step sections were combined. The incidence of mineralization of the renal papilla was significantly increased in 1,000 ppm males. The incidence of mononuclear cell leukemia in 1,000 ppm males was significantly increased compared to the chamber controls. In the nose, the incidences of basal cell hyperplasia were significantly increased in all exposed groups of males and females, and the incidences of degeneration of the olfactory epithelium were increased in 1,000 ppm males and females and 300 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 600 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival of all exposed male and female mice was similar to that of the chamber control groups. Mean body weights of 600 ppm males were less than those of the chamber control group throughout the study, and those of 600 ppm females were less after week 13. The mean body weights of 300 ppm males and females were less than those of the chamber controls during much of the study, but these groups recovered by the end of the study. The incidences of hepatocellular adenoma or carcinoma (combined) were significantly increased in the 100 and 600 ppm males and in all exposed groups of females. The incidences of hepatocellular adenoma were significantly increased in all exposed groups of females, and the incidences in all exposed groups of males and females exceeded the historical range for chamber controls. The incidences of hepatocellular carcinoma and eosinophilic foci of the liver were significantly increased in 600 ppm females. The incidences of olfactory epithelial metaplasia and hyperplasia of the glands overlying the olfactory epithelium were significantly increased in all exposed groups of males and females. In addition, atrophy of the olfactory epithelium was significantly increased in 300 and 600 ppm males. The incidence and severity of nephropathy were increased in 600 ppm females compared to chamber controls. Epithelial hyperplasia of the forestomach also was present in male mice. GENETIC TOXICOLOGY: alpha-Methylstyrene was not mutagenic in four strains of Salmonella typhimurium, with or without rat or hamster liver metabolic activation enzymes (S9). alpha-Methylstyrene did not induce chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9 activation, but did significantly increase the frequency of sister chromatid exchanges in cultures exposed in the presence of S9. In vivo, no significant increases in the frequencies of micronucleated erythrocytes were seen in blood samples of male mice obtained at the conclusion of the 3-month study. However, in female mice from the 3-month study, a significant increase in micronucleated erythrocytes was observed in the 1,000 ppm group. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of alpha-methylstyrene in male F344/N rats based on increased incidences of renal tubule adenomas and carcinomas (combined). The increased incidence of mononuclear cell leukemia in 1,000 ppm male F344/N rats may have been related to alpha-methylstyrene exposure. There was no evidence of carcinogenic activity of alpha-methylstyrene in female F344/N rats exposed to 100, 300, or 1,000 ppm. There was equivocal evidence of carcinogenic activity of alpha-methylstyrene in male B6C3F1 mice based on marginally increased incidences of hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of alpha-methylstyrene in female B6C3F1 mice based on increased incidences of hepatocellular adenomas and carcinomas. Exposure of rats to alpha-methylstyrene resulted in kidney toxicity, which in males exhibited some features of alpha2μ-globulin nephropathy. Exposure to alpha-methylstyrene resulted in nonneoplastic lesions of the nose in male and female rats and mice and of the liver and kidney in female mice.     

Developmental Toxicity of Dimethylacetamide by Inhalation in the Rat

Developmental Toxicity of Dimethylacetamide by Inhalation inthe Rat. SOLOMON, H. M., FERENZ, R. L., KENNEDY, G. L., ANDSTAPLES, R. E. (1991). Fundam. Appl. Toxicol. 16, 414–422.Dimethylacetamide (DMAC) is a widely used industrial solvent.It has been reported to be teratogenic when given to rats byinjection or following dermal application. Most of these studiesemployed large single doses and did not examine both the fetaland the maternal response. In this study, groups of pregnantCrl:CD rats were exposed to 32, 100, or 282 ppm DMAC by inhalationfor 6 hr/day from Days 6 through 15 of gestation (day on whichcopulation plug was detected was termed Day 1G). A control groupof chambered pregnant rats was exposed simultaneously to aironly. All female rats were euthanized on Day 21G. At 282 ppm,both maternal weight gain during the exposure period and fetalweight were significantly decreased and accompanied by a significantdose-response trend. These effects were not seen in rats inhalingeither 32 or 100 ppm. Fetal resorptions were not increased inany of the groups exposed to DMAC. Fetal incidences of external,visceral, or skeletal variations and malformations were similarbetween the test and control groups. Therefore, both fetal andmaternal toxicity were noted at 282 ppm and the no-observedadverse-effect level under these experimental conditions was100 ppm for both the dam and the conceptus. DMAC was not demonstratedto produce malformations in the rat fetus even at a level thatwas toxic to the dam.     

Assessment of adult and neonatal reproductive parameters in Sprague-Dawley rats exposed to propylene glycol monomethyl ether vapors for two generations.

This study evaluated propylene glycol monomethyl ether (PGME) in a rat 2-generation reproduction study, which included non-traditional study end points, such as sperm count and motility, developmental landmarks, estrous cyclicity, and weanling organ weights. Groups of 30 male and 30 female Sprague-Dawley rats (6-weeks-old) were exposed to 0, 300, 1000, or 3000 ppm of PGME vapors via inhalation for 6 hours/day, 5 days/week prior to mating, and 6 hours/day, 7 days/week during mating, gestation, and lactation, for 2 generations. These concentrations corresponded to estimated oral equivalent doses of 0, 396, 1325, or 3974 mg/kg/day. At 3000 ppm, toxicity in the P1 and P2 adults was marked, as evidenced by sedation during and after exposure, and mean body weights which were as much as 21% lower than controls. This marked parental toxicity was accompanied by lengthened estrous cycles, decreased fertility, decreased ovary weights, and histologic ovarian atrophy in maternal rats. In the offspring from these dams, decreased body weights, reduced survival and litter size, slight delays in puberty onset, and histologic changes in liver and thymus in the F1 and F2 offspring were observed. The nature of the reproductive/neonatal effects and their close individual animal correlation with decreased maternal body weights suggested that these effects were secondary to general toxicity and/or nutritional stress. No such reproductive/neonatal effects were observed at 1000 ppm, a concentration which caused less marked, but significant body weight effects without sedation. There were no treatment-related effects of any kind noted at 300 ppm of PGME. Therefore, the no-observable-effect level (NOEL) for reproductive/neonatal effects was 1000 ppm, and that for parental toxicity was 300 ppm.