Carcinogenicity study in rats of phytic acid 'Daiichi', a natural food additive.

The carcinogenicity of phytic acid 'Daiichi' (PA), a natural food additive, was examined in Fischer 344 rats of both sexes. PA was added to the drinking-water of groups of 60 male and 60 female rats at levels of 1.25 or 2.5% for 100-108 wk. There was a dose-dependent reduction in the mean final body weights of rats treated with PA. Necrosis and calcification of the renal papillae were observed in PA-treated rats, but not in the controls. The incidences of necrosis (calcification) were as follows: one (three) out of 57 males given 2.5% PA; one (none) out of 59 males given 1.25% PA; 10 (17) out of 55 females given 2.5% PA; six (six) out of 58 females given 1.25% PA. Renal papillomas occurred in three of the high-dose male rats, four of the high-dose female rats, and three of the low-dose female rats. The development of papillomas seemed to be related to calcification and necrosis of the renal papillae induced by PA. While many other tumours developed in all groups, including the controls, the organ distribution of these neoplasms and their histological characteristics did not differ significantly from those known to occur spontaneously in this strain of rats.     

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.     

Alpha 2u-globulin nephropathy and carcinogenicity following exposure to decalin (decahydronaphthalene) in F344/N rats.

Decalin (decahydronaphthalene) is a widely used industrial solvent known to cause male rat-specific alpha2u-globulin nephropathy. In this project, 13-week and two-year inhalation studies of decalin were conducted consecutively in both sexes of F344/N rats. The key objectives were to (1) characterize the 13-week toxicity of decalin in rats, with an emphasis on nephropathy in males; (2) compare the kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in males over 2 to 13 weeks of decalin exposure; and (3) correlate male rat nephropathy observed in the 13-week study with renal carcinogenicity in the two-year study. F344 rats (M/F) were exposed via whole-body inhalation to 0, 25, 50, 100, 200, or 400 ppm decalin for 13 weeks. Urine was collected at weeks 2 and 6 for creatinine and decalol analyses and at week 12 for clinical urinalysis. Right kidneys were collected from male rats at weeks 2 and 6 and from both sexes at week 13, homogenates were prepared using the whole kidney, and these homogenates were analyzed for alpha2u-globulin, decalin, and 2-decalone. Left kidneys were evaluated for histopathology and cell proliferation utilizing a proliferating cell nuclear antigen technique and counting proximal renal tubular epithelial cells to determine cell labeling indices. Necropsies and histopathologic evaluations were performed at week 13. Decalin exposure caused increases in kidney weight, urinalysis parameters (protein, AST, LDH), kidney alpha2u-globulin concentration, and proximal convoluted renal tubular cell proliferation in males. These changes were accompanied by microscopic lesions (accumulation of hyaline droplets in cortical tubules, regeneration of proximal tubular epithelium, and granular casts in medullary tubules) clearly linked to alpha2u-globulin nephropathy. Both decalin and 2-decalone were related to increased alpha2u-globulin in male kidneys. Kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in exposed females were negligible, while females excreted greater amounts of decalol metabolites in urine than males at weeks 2 and 6. There were no exposure-related microscopic lesions in females. For chronic exposure, F344 rats were exposed via whole-body inhalation to 0, 25, 50 (males only), 100, or 400 ppm decalin for two years. Chronic exposure induced a spectrum of nonneoplastic and neoplastic lesions in the renal cortex of males, ranging from regenerative lesions of chronic nephropathy to tubular carcinomas. Incidences of renal tubular adenoma, tubular carcinoma, combined tubular adenomas and carcinomas, cortical tubular hyperplasia, hyaline droplet accumulation, hyperplasia of pelvic epithelium, and mineralization in renal papilla were increased in exposed males compared to controls. There was a clear increase in the mean severity of chronic nephropathy in decalin-exposed males. It was concluded that the carcinogenic effect on the renal cortical epithelium of male rats exposed to decalin was related to increased turnover of this epithelium, resulting from the cytotoxic effects of alpha2u-globulin accumulation in the renal cortical tubular cell cytoplasm.     

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.     

Sub-chronic (13-week) oral toxicity study in rats with recombinant human lactoferrin produced in the milk of transgenic cows.

The oral toxicity of recombinant human lactoferrin (rhLF) produced in the milk of transgenic cows was investigated in Wistar rats by daily administration via oral gavage for 13 consecutive weeks, 7 days per week. The study used four groups of 20 rats/sex/dose. The control group received physiological saline and the three test groups received daily doses of 200, 600 and 2000 mg of rhLF per kg body weight. Clinical observations, growth, food consumption, food conversion efficiency, water consumption, neurobehavioural testing, ophthalmoscopy, haematology, clinical chemistry, renal concentration test, urinalysis, organ weights and gross examination at necropsy and microscopic examination of various organs and tissues were used as criteria for detecting the effects of treatment. Overall, no treatment-related, toxicologically significant changes were observed. The few findings that may be related to the treatment (lower cholesterol in high-dose females, lower urinary pH in high-dose males and females and very slightly higher kidney weight in high-dose females) were considered of no toxicological significance. Based on the absence of treatment-related, toxicologically relevant changes, the no-observed-adverse-effect level (NOAEL) was considered to be at least 2000 mg/kg body weight/day.     

A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats.

This study was conducted to evaluate the safety of l-theanine (Suntheanine) when administered as a dietary admixture to male and female Crl:CD (SD)GS BR rats at concentrations providing doses of 0, 1500, 3000 or 4000 mg/kg bw/day for 13 weeks. The study design was consistent with OECD Guideline 408 and USFDA Redbook II (1993) and GLP. There were no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, hematology, or urinalysis. There were no consistent treatment-related adverse effects in gross pathology, organ weights or ratios or histopathology. The increased incidence of renal tubular cell adenomas in high-dose females only were not consistent with the characteristics of a renal carcinogen (due to early onset and low number of animals affected) but were more consistent with a genetic predisposition than with direct organ toxicity. The no-observed-adverse-effect-level (NOAEL) was 4000 mg/kg bw/day, the highest dose tested.     

Pathological outcomes in kidney and brain in male Fischer rats given dietary ochratoxin a, commencing at one year of age

Malignant renal carcinoma, manifest in morbid ageing rats, is the striking component of an otherwise silent response after about nine months of exposure to ochratoxin A in the first year of life (daily intake ~100-250 μg/kg body weight). Reasons for the long latency are unclear, as is whether there would be a similar carcinogenic response if toxin exposure started at one year of age. Therefore, 24 male Fischer rats were given 100 μg ochratoxin A as a daily dietary contaminant for 35 weeks from age 50 weeks. Plasma ochratoxin A concentration reached a maximum value of ~8 μg/mL within one month of starting the toxin regimen. No renal carcinomas occurred. Four renal adenomas, two of which were only microscopic, were found among the six rats surviving for 110 weeks. The findings raise new questions about a difference between young adults and mature adults in sensitivity of male rats to the ochratoxin A-induced DNA damage necessary for renal carcinogenesis. A pilot histological study of perfuse-fixed brains of the toxin-treated rats showed no gross abnormalities, correlating with the consistent absence of behavioral or neurological disorders from chronic ochratoxin A exposure regimens in the range 100-250 μg/kg/day during the second half of life. Reasoned questioning concerning ochratoxin A as a neurotoxic mycotoxin is made.     

Prechronic Toxicity Studies on 2-Ethylhexanol in F334 Rats and B6C3F1 Mice

Data on the subchronic toxicity of 2-ethylhexanol (2EH) wererequired to establish the dose vehicle and dose levels for oncogenicitystudies. In preliminary studies 2EH was given subacutely (11days) to male and female Fischer 344 rats and B6C3F1 mice asan aqueous emulsion by oral gavage (0, 100, 330, 1000, and 1500mg/kg/day). Clinical observations were made, body weights, foodconsumption, clinical chemistries, hematologies, and selectedorgan weights were measured, and gross and micropathologieswere performed. Target organs were the central nervous system,liver, forestomach, spleen, thymus, and kidney in rats and thecentral nervous system, liver, and forestomach in mice. 2EHwas then administered by oral gavage to male and female F344rats and B6C3F1 mice as an aqueous emulsion (0, 25, 125, 250,and 500 mg/kg/day) for 13 weeks. At 500 mg/kg/day in the ratthere was reduced body weight gain (6% male, 7% female), increasedrelative liver (29% male, 15% female), kidney (16% male, 6%female), stomach (11% male, 16% female), and testes (6%) weights,and moderate gross and microscopic changes in the liver andforestomach. There were no behavioral effects or effects onthe spleen or thymus. A no-effect level for target organ effectsin the rat was 125 mg of 2EH/kg/day. At 500 mg of 2EH/kg/dayin the mouse the only effects were increased relative stomachweights in males (13%) and a low incidence of gross and microscopicfindings in the forestomach (male and female) and liver (female).A no-effect level for target organ effects in the mouse was125 mg of 2EH/kg/day. 2EH was a peroxisome proliferator in therat but not in the mouse at subchronic dose levels of 500 mg/kg/day.Dose levels in oncogenicity studies were set at 50 mg/kg/dayfor the absence of treatment-related effects in rats and mice,and 500 and 750 mg/kg/day, respectively, in rats and mice ashigh doses producing minimal toxicity without altering the lifespan.     

Safety profile of thalidomide after 53 weeks of oral administration in beagle dogs.

Fifty-six adult beagle dogs (28 male, 28 female) were orally administered thalidomide at 43, 200, or 1000 mg/kg/day for 53 weeks. Sixteen (2/sex/dose group) and 32 (4/sex/dose group) dogs were euthanized and necropsied after 26 and 53 weeks of dosing, respectively. The remaining 8 animals (2/sex/group; high-dose and control groups) were dosed for 53 weeks, euthanized, and necropsied at 58 weeks after a 5-week recovery period. There were no deaths during the study. The only observed clinical signs attributable to thalidomide administration were green-colored urine, white-colored fecal residue presumed to be unchanged thalidomide, enlarged and/or blue coloration of female mammary tissue, and prolonged estrus. There were no thalidomide-related changes in body weights, food consumption, electrocardiography, ophthalmoscopy, neurological function, and endocrine function. The mostly slight and/or transient variations observed in some hematology and blood chemistry values of dosed dogs were considered to be toxicologically insignificant and were supported by the lack of histopathologic correlates. The only gross finding attributable to thalidomide was a yellow-green discoloration of the femur, rib, and/or calvarium that was observed at each euthanization interval including recovery. There was no microscopic correlate for this finding. No thalidomide-related microscopic changes were seen in any of the organs and tissues at 26 weeks. Mammary duct dilatation and/or glandular hyperplasia observed in females at 53 and 58 weeks and hepatic bile pigment exhibited by high-dose males at 53 weeks were microscopic changes considered to be thalidomide-related. There was no gross and histopathologic evidence of any tumors. In summary, thalidomide at up to 1000 mg/kg/day for 53 weeks did not induce any major systemic toxicity or tumors in dogs. The NOAEL was 200 mg/kg/day.     

Toxicity of methyl tertiary‐butyl ether (MTBE) following exposure of Wistar Rats for 13 weeks or one year via drinking water

Thirteen‐week and one‐year toxicity studies of methyl tertiary‐butyl ether (MTBE) administered in drinking water to Wistar rats were conducted. Male and female rats were exposed to MTBE in drinking water at 0.5, 3, 7.5 and 15 mg ml^?1 for 13 weeks and at 0.5, 3 and 7.5 (males) or 0.5, 3 and 15 mg ml^?1 (females) for 1 year. Body weights were reduced only in males following 13 weeks of exposure. Reduced water consumption and urine output were observed in males and females exposed to MTBE. Kidney cell replication and α_2u‐globulin levels in males were increased at 1 and 4 weeks of MTBE exposure and tubular cell regeneration was increased in male kidneys exposed to MTBE concentrations of 7.5 mg ml^?1 or greater for 13 weeks. Wet weights of male kidneys were increased following 13 weeks, 6 months and 1 year of exposure to MTBE concentrations of 7.5 mg ml^?1 or greater. Kidney wet weights were increased in females at MTBE concentrations of 15 mg ml^?1 for 13 weeks. Tertiary‐butyl alcohol blood levels increased linearly with dose in males and females following 1 year of exposure. Chronic progressive nephropathy (CPN), of minimal to mild severity, increased in males, but not females, with 1 year of MTBE exposure. In summary, exposure of Wistar rats to MTBE in the drinking water resulted in minimal exposure‐related effects including limited renal changes in male rats suggestive of α_2u‐globulin nephropathy following 13 weeks of exposure and an exacerbation of CPN in males at the end of 1 year of exposure. Copyright © 2011 John Wiley & Sons, Ltd.     

Subchronic inhalation study of 1-hexene in Fischer 344 rats.

The objective of this study was to evaluate the toxicity of 1-hexene following repeated inhalation exposures in male and female Fischer 344 rats. Groups of 40 male and 40 female rats were exposed for 6 hours per day, 5 days per week, over a 13-week period. Treatment groups consisted of air-exposed control (0 ppm) and three test groups of 300, 1000, and 3000 ppm 1-hexene. During the treatment period, the rats were observed daily for clinical signs of toxicity; body weights and neuromuscular coordination [females only] were measured at 7-day intervals. After 7 weeks of exposure and at the end of the treatment period, the rats were subject to macroscopic and microscopic pathology, clinical chemistry, hematology, urinalysis, and sperm counts. No mortalities were observed during the course of the study. No clinical signs of toxicity attributable to 1-hexene exposure were observed. Female rats exposed to 3000 ppm had significantly lower body weights compared to control rats from exposure day 5 persisting throughout the treatment period. Male rats exposed to 3000 ppm had slightly but not statistically significant lower body weights in comparison to controls. Male rats exhibited slightly increased absolute and relative testicular weights, and female rats had slightly decreased absolute [but not relative] liver and kidney weights, at 3000 ppm. There were no gross or microscopic morphological findings attributed to treatment. Exposure to 1-hexene did not affect neuromuscular coordination in females as determined using the Rotarod, nor sperm counts in male rats. Several statistically significant effects in hematology, clinical chemistry, and urinalysis evaluations were observed, but were either of small magnitude or did not correlate with histopathological findings, and thus did not appear to be of biological significance. In summary, the no-adverse-effect-level for this study was determined to be 1000 ppm, based on decreased weight gain in female rats, and on slight organ weight changes in both sexes at 3000 ppm.     

13-Week oral toxicity study with isomaltulose (Palatinose) in rats.

The potential subchronic oral toxicity of isomaltulose (Palatinose) was examined by administering this substance in the diet to groups of 20 male and 20 female Wistar rats at levels of 0, 2.5, 5 and 10% for 13 consecutive weeks. Daily clinical observations, body weight, food conversion efficiency, food and water consumption were not affected at any stage of the study. Ophthalmoscopy, haematology, clinical chemistry, urinalysis, organ weights, gross and histopathological examination, neurobehavioural observations, motor activity assessment and the results of an immunotoxicity screen did not reveal any abnormalities related to the ingestion of the test substance. In conclusion, the administration of isomaltulose at dietary levels up to 10% for 13 consecutive weeks was well tolerated without any signs of toxicity. The overall intake at this level corresponded to 7.0 and 8.1 g/kg body weight/day in male and female rats, respectively.     

Short-term toxicity of 2,6-dimethylhept-5-en-1-al in rats

Groups of 15 male and 15 female rats were fed for at least 90 days on diets that provided 2,6-dimethylhept-5-en-1-al (DMH) at average intakes of 0 (control), 9, 37 and 150 mg/kg body weight/day. Steps were taken to limit loss of DMH during diet mixing, storage and feeding. No effects attributable to treatment were encountered in body weight, food intake, water intake, haematology (at wk 6 and 13) or the gross and microscopic pathological examinations. At the highest dose level there was a slight reduction in renal concentrating ability at wk 6 in males and wk 14 in females, together with a small increase in relative kidney weight and liver weight in females. The serum-glucose concentrations of both sexes on the highest dose were elevated compared with the controls. It was concluded that the intermediate dose, providing an intake of 37 mg/kg/day, was the no-untoward-effect level.     

TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS: INHALATION SUBCHRONIC TOXICITY/NEUROTOXICITY STUDY OF A LIGHT CATALYTIC REFORMED NAPHTHA DISTILLATE IN RATS

A 13-wk whole-body inhalation study was conducted with Sprague-Dawley CD rats (16/sex/group) exposed to a light catalytic reformed naphtha distillate (LCRN-D, CAS number 64741-63-5) at target concentrations of 0, 750, 2500, and 7500 ppm for 6 h/d, 5 d/wk. Sixteen rats per sex in the control and high-dose groups were maintained after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, throughout exposure and after the recovery period. Neuropathology was evaluated at termination. No test-related mortality or effects on physical signs, body weight, food consumption, or clinical chemistry were observed. In males exposed to 7500-ppm LCRN-D, a statistically significant decrease in white blood cell counts and lymphocyte counts was observed at the termination of exposure that was not present in animals after the 4-wk recovery period. However, mean corpuscular volume was slightly decreased in high-dose males after the recovery period. Statistically significant increases in kidney weights relative to body weights in 7500-ppm male rats correlated with microscopically observed hyaline droplet formation and renal tubule dilation, indicative of light hydrocarbon nephropathy, a condition in male rats that is not toxicologically significant for humans. Statistically significant decrease in absolute and relative spleen weights in 7500-ppm male rats correlated with decreases in hematologic parameters but had no microscopic correlate and was not observed in animals after 4 wk of recovery. This mild, reversible effect in white blood cell populations may relate to the presence of aromatics in the distillate. The only effect of LCRN-D on neurobehavioral parameters was significantly higher motor activity counts among high-dose (7500 ppm) males after the 4-wk recovery period, suggesting a possible delayed effect of LCRN-D. However, there was no evidence of hyperactivity or abnormal behavior from the functional observational battery evaluations, and there were no microscopic changes in neural tissue to support this observation. The no-observed-adverse-effects level (NOAEL) for LCRN-D was 2500 ppm for both subchronic toxicity and neurotoxicity. The no-observed-effects level (NOEL) was 750 ppm.     

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic reformed naphtha distillate in rats

A 13-wk whole-body inhalation study was conducted with Sprague-Dawley CD rats (16/sex/group) exposed to a light catalytic reformed naphtha distillate (LCRN-D, CAS number 64741-63-5) at target concentrations of 0, 750, 2500, and 7500 ppm for 6 h/d, 5 d/wk. Sixteen rats per sex in the control and high-dose groups were maintained after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, throughout exposure and after the recovery period. Neuropathology was evaluated at termination. No test-related mortality or effects on physical signs, body weight, food consumption, or clinical chemistry were observed. In males exposed to 7500-ppm LCRN-D, a statistically significant decrease in white blood cell counts and lymphocyte counts was observed at the termination of exposure that was not present in animals after the 4-wk recovery period. However, mean corpuscular volume was slightly decreased in high-dose males after the recovery period. Statistically significant increases in kidney weights relative to body weights in 7500-ppm male rats correlated with microscopically observed hyaline droplet formation and renal tubule dilation, indicative of light hydrocarbon nephropathy, a condition in male rats that is not toxicologically significant for humans. Statistically significant decrease in absolute and relative spleen weights in 7500-ppm male rats correlated with decreases in hematologic parameters but had no microscopic correlate and was not observed in animals after 4 wk of recovery. This mild, reversible effect in white blood cell populations may relate to the presence of aromatics in the distillate. The only effect of LCRN-D on neurobehavioral parameters was significantly higher motor activity counts among high-dose (7500 ppm) males after the 4-wk recovery period, suggesting a possible delayed effect of LCRN-D. However, there was no evidence of hyperactivity or abnormal behavior from the functional observational battery evaluations, and there were no microscopic changes in neural tissue to support this observation. The no-observed-adverse-effects level (NOAEL) for LCRN-D was 2500 ppm for both subchronic toxicity and neurotoxicity. The no-observed-effects level (NOEL) was 750 ppm.     

Effects of corticosterone on reproduction in male sprague-dawley rats

Corticosterone, the predominant circulating adrenal corticosteroid in rodents, was investigated for its effects on reproduction in male Sprague-Dawley rats. Male rats (in groups of 50, 25, and 50) were administered corticosterone at doses of 0,10, and 25 mg/kg/d, respectively, by subcutaneous injection once daily for 6 weeks; the highest dose was decreased to 20 mg/kg/d after 15 d. During the last 2 weeks of the 6-week treatment period, 25 males per group were paired with untreated females. The remaining 25 males from the 0 and 25/20 mg/kg/d groups were allowed a 6-week recovery period and, during the last 2 weeks of this period, these males were also paired with untreated females. At the end of the treatment period, the males had markedly elevated plasma corticosterone concentrations and decreased weight gain. They also produced fewer copulatory plugs than controls, which may have been secondary to observed adverse effects on the accessory sex organs (decreased weights and microscopic changes in prostate and seminal vesicles). However, no adverse effects on sperm motility, sperm count, or microscopic features of the testes were observed. Serum testosterone concentration of the high-dose males was elevated, but luteinizing hormone was unaffected. The numbers of embryonic implantation sites and live fetuses in females mated to these males were reduced. All of these effects except decreased prostate weights were reversible upon cessation of corticosterone administration. Thus, exogenous administration of corticosterone to male rats produced reversible effects on implant count and litter size of female rats mated to these males. These effects on male rat reproduction may have been secondary to reduced accessory sex organ function, which resulted in diminished secretions and fewer copulatory plugs.     

Subchronic Inhalation Study of 1-Hexene in Fischer 344 Rats

ABSTRACT

The objective of this study was to evaluate the toxicity of 1-hexene following repeated inhalation exposures in male and female Fischer 344 rats. Groups of 40 male and 40 female rats were exposed for 6 hours per day, 5 days per week, over a 13-week period. Treatment groups consisted of air-exposed control (0 ppm) and three test groups of 300, 1000, and 3000 ppm 1-hexene. During the treatment period, the rats were observed daily for clinical signs of toxicity; body weights and neuromuscular coordination [females only] were measured at 7-day intervals. After 7 weeks of exposure and at the end of the treatment period, the rats were subject to macroscopic and microscopic pathology, clinical chemistry, hematology, urinalysis, and sperm counts. No mortalities were observed during the course of the study. No clinical signs of toxicity attributable to 1-hexene exposure were observed. Female rats exposed to 3000 ppm had significantly lower body weights compared to control rats from exposure day 5 persisting throughout the treatment period. Male rats exposed to 3000 ppm had slightly but not statistically significant lower body weights in comparison to controls. Male rats exhibited slightly increased absolute and relative testicular weights, and female rats had slightly decreased absolute [but not relative] liver and kidney weights, at 3000 ppm. There were no gross or microscopic morphological findings attributed to treatment. Exposure to 1-hexene did not affect neuromuscular coordination in females as determined using the Rotarod®, nor sperm counts in male rats. Several statistically significant effects in hematology, clinical chemistry, and urinalysis evaluations were observed, but were either of small magnitude or did not correlate with histopathological findings, and thus did not appear to be of biological significance. In summary, the no-adverse-effect-level for this study was determined to be 1000 ppm, based on decreased weight gain in female rats, and on slight organ weight changes in both sexes at 3000 ppm.     

Effects of Coumarin Following Perinatal and Chronic Exposure in Sprague-Dawley Rats and CD-1 Mice

Coumarin, a naturally occurring substance most frequently usedas a fragrance enhancer and stabilizer, was administered inthe diet of Sprague-Dawley rats at dose levels of 0, 333, 1000,2000, 3000, and 5000 ppm or in the diet of CD-1 mice at doselevels of 0, 300, 1000, or 3000 ppm. Rats receiving 333, 1000,and 2000 ppm coumarin were exposed to these dose levels in uteroand during the lactational period, then chronically followingweaning. Rats in the 3000- and 5000-ppm dose groups and allmice received only postweanlng chronic exposure. All male ratswere terminated after 104 weeks of postweaning exposure; femalerats were terminated after 110 weeks. Male mice were terminatedat Week 101 and female mice at Week 109. Among rats, survivalwas decreased at 333 ppm, but signilicantly increased amongrats in the 3000- and 5000-ppm dose groups. Dramatic dose-relateddecreases in body weight gain were recorded for rats receiving2000, 3000, and 5000 ppm, clearly indicating that the MTD (maximumtolerated dose, as indicated by a body weight decrement of greaterthan 10–15%) was exceeded. Food consumption also was decreasedat the three highest dose levels, although body weight decrementwas disproportionately large compared to changes in food consumption.Treatment-related decreases in hemoglobin were recorded fromWeek 6 onward. Minimal treatment-related changes in he matologyand clinical chemistry were recorded. Increased liver weightswere observed for male and female rats receiving 3000 or 5000ppm and for females only at 1000 and 2000 ppm. Increased incidencesof cholanglofibroma, cholangiocarcinoma, and parenchymal livercell tumors were observed among male and female rats receiving5000 ppm. One male rat receiving 3000 ppm devel oped a cholangiocarcinoma;no tumor increase was observed in males or females at 2000 ppmor below. Coumarin, at a dose clearly exceeding the MTD can,therefore, induce liver tumors in rats, although survival, relativeto controls, was increased at the same dose levels. Among mice,a decrease in body weight gain was reported for males in the1000- and 3000-ppm dose groups during the first 52 weeks ofthe study. No dose-related abnormalities in clinical signs,clinical pathology, hematology, or gross or microscopic pathologywere noted.     

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.     

Tumors of the Bladder, Kidney, and Intestine of F344 Rats and Liver of B6C3F1 Mice Administered o-Nitroanisole in Feed

Tumors of the Bladder, Kidney, and Intestine of F344 Rats andLiver of B6C3F₁ Mice Administered o-Nitroanisole in Feed. IRWIN,R. D., CHHABRA, R., EUSTIS, S., PINTER, A., AND PREJEAN, J.D. 1996). Fundam. Appl. Toxicol. 30, 1–12. o-Nitroanisole, a mutagenic intermediate used in the manufactureof azo dyes, was administered in feed for 2 years at concentrationsof 0, 222, 666, or 2000 ppm to groups of 60 male and 60 femaleF344 rats. No significant increase in neoplasms occurred inthese groups of rats. Additional (stop exposure) groups of 60male and 60 female F344 rats received diets containing 0, 6000,or 18,000 ppm for 27 weeks followed by maintenance on controldiets for up to an additional 77 weeks. Survival of the stopexposure groups was reduced because of the development of chemicalrelated neoplasms of the urinary bladder. After 13, 28, 40,and 65 weeks on study, 10 rats per group were necropsied andevaluated for the presence of chemical associated lesions. Hyperplasiaof the epithelium of the urinary bladder was significantly increasedat all interim evaluations. A transitional cell carcinoma wasobserved at the 13-week evaluation in one male rat that received18,000 ppm and thereafter transitional cell neoplasms of thebladder were present in male and female rats at each interimevaluation. Adeno matous polyps of the large intestine weresignificantly increased in groups that received 6000 or 18,000ppm. In addition carcino mas of the large intestine were presentin four males and two females that received 18,000 ppm. Hyperplasiaof the transitional epithelium of the renal pelvis was significantlyincreased in groups of rats that received 6000 or 18,000 ppmand transitional cell papillomas were observed in three malesand one female that received 18,000 ppm. Transitional cell carcinomasof the kidney occurred in one male that received 6000 ppm andsix males and one female that received 18,000. Groups of 60male and 60 female B6C3F₁, mice received dietary concentrationsof 0, 666, 2000, or 6000 ppm o-nitroanisole for 2 years. Nostop exposure study was conducted with mice. The only neoplasticresponse observed in mice was in the liver of males; hepatocellularadenomas or carcino mas were increased in groups of male micethat received 2000 or 6000 ppm. No increase in neoplasms associatedwith chemical exposure occurred in female mice.