Reproductive Toxicity Study In Rats Research Articles

3-Nitrooxypropanol (Feed Additives).

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of 3-nitrooxypropanol (3-NOP) (CAS No. 100502-66-7), using the evaluation documents for feed additive designation. This feed additive is a nitrate ester of 1,3-propanediol developed to reduce methane generated in the first stomach of cattle (rumen). The data used in the assessment include the fate in animals (mice, rats, cattle), residues (cattle), genotoxicity, acute toxicity (rats), subacute toxicity (mice, rats and dogs), chronic toxicity/carcinogenicity (rats), reproductive/developmental toxicity (rats and rabbits), and others. The lowest no-observed-adverse-effect level (NOAEL) for possible adverse effects of 3-NOP was 100 mg/kg bw per day in 52-chronic toxicity, 104-week chronic toxicity/carcinogenicity, and two-generation reproductive toxicity studies in rats. Given this, FSCJ specified an acceptable daily intake (ADI) of 1 mg/kg bw per day by applying a safety factor of 100 to the NOAEL.

Effects of endocrine disruptor furan on reproductive physiology of Sprague Dawley rats: An F1 Extended One-Generation Reproductive Toxicity Study (EOGRTS).

The present study investigated the reproductive toxicity of furan in an Extended One-Generation Reproductive Toxicity Study in rats. Sprague Dawley F0 weaning rats (30 per sex per group) were exposed to furan orally at 0, 1, 2.5, 5, and 10 mg kg-1 for 10 weeks (males) and 2 weeks (females) and then mated. Results of F0 indicated that in the furan-treated groups (5 mg kg-1 and 10 mg kg-1), body weight (bw) gain decreased during prebreed and gestational period while increased during lactation periods. F0 animals prebreeding exposure resulted in head tilt and foot splay at 10 mg kg-1. Number of live pups at birth were decreased (p < 0.001) at 10 mg kg-1. At postnatal day (PND) 70, a significant (p = 0.03) decrease in testosterone levels of male rats and estrogen levels of female rats (p = 0.05) was observed in 10 mg kg-1 furan-treated group in F1 generation. Luteinizing hormone, follicle-stimulating hormone, and progesterone levels were also reduced, but their reduction was not statistically significant in all groups. In higher dose furan group (10 mg kg-1), testicular and ovarian weights were reduced in F1 generation at PND 70, with decreased daily sperm production (p = 0.01) and disturbed estrous cyclicity (p < 0.01). Some histopathological changes were also observed in testis and ovaries in groups whose parents were previously exposed to 10 mg kg-1 bw of furan group. Based on the above results, it is suggested that exposure to food-based contaminant furan induced remarkable changes in the F0 (parental stage) and F1 (offspring, pubertal, and adult stage) generations of Sprague Dawley rats.

Flometoquin (Pesticides).

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of flometoquin (CAS No. 875775-74-9), a quinoline insecticide, based on results from various studies. Major adverse effects of flometoquin observed were suppressed body weight and hepatocellular steatosis in rats, and ovarian atrophy with decreased numbers of small follicle in rats and mice. Neither teratogenicity nor genotoxicity relevant to human health was detected. Increased incidences of gonadal stromal tumor in female rats and of small intestine adenocarcinomas in male mice were identified in carcinogenicity studies. Genotoxic mechanisms were, however, unlikely involved in their tumor developments, and these enabled FSCJ to establish a threshold in the assessment. Mechanism and toxicity studies suggested that ovarian atrophy triggered the development of gonadal stromal tumor, through continuous stimulation of gonadotropin to the gonadal stroma, via negative feedback. A reproductive study showed the decreases in numbers of small follicle, implantation and also in litter size. Based on the results from various studies, flometoquin (parent compound only) was the residue definition for dietary risk assessment in agricultural products. The lowest no-observed-adverse-effect level (NOAEL) obtained from all the studies was 0.8 mg/kg bw/day in a developmental toxicity study in rabbits. FSCJ specified an acceptable daily intake (ADI) of 0.008 mg/kg bw/day by applying a safety factor of 100 to the NOAEL. FSCJ recognized that in considering the ambiguity of the underlying mechanism, the adverse effect on small follicle possibly occurred after single oral administration of flometoquin. Thus FSCJ specified an acute reference dose (ARfD) to be 0.044 mg/kg bw by applying a safety factor of 100 to the NOAEL of 4.45 mg/kg bw per day in a two-generation reproductive toxicity study in rats, based on a comprehensive evaluation of NOAEL for ovarian toxicity.

Fenquinotrione (Pesticides).

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of fenquinotrione (CAS No. 1342891-70-6), a triketone herbicide, based on results from various studies. A major adverse effect of fenquinotrione was observed in ocular toxicity characterized as keratitis in rats, which is often observed with other 4-hydroxyphenylpyruvate dioxygenase (4-HPDDase) inhibitors in this species. Other effects included were centrilobular hepatocytes hypertrophy, and also cholecystolithiasis in mice. No effects were observed on neurotoxicity, fertility, teratogenicity and genotoxicity. A corneal squamous cell carcinoma found in a male rat, at a sub-highest dose in a two-year carcinogenicity study, was judged to be treatment-related, because this tumor is rare in rats. The occurrence was considered to be attributed to persistent stimulation of inflammation including keratitis. In addition, negative results were obtained from all of the genotoxicity studies. Therefore, a genotoxic mechanism was unlikely involved in the tumor development, and it enabled FSCJ to establish a threshold in the assessment. Fenquinotrione (parent compound only) was the residue definition for dietary risk assessment in agricultural products. The lowest no-observed-adverse-effect level (NOAEL) obtained from all the studies was 0.166 mg/kg bw/day in a two-generation reproductive toxicity study in rats. FSCJ specified an acceptable daily intake (ADI) of 0.0016 mg/kg bw/day by applying a safety factor of 100 to the NOAEL. The lowest-observed-adverse-effect-level (LOAEL) for potential adverse effects of a single oral administration of fenquinotrione was 2,000 mg/kg bw based on soft feces and staining of perianal fur observed within one day after the oral administration in an acute toxicity study in rats. Thus the acute reference dose (ARfD) is not necessary, since the LOAEL was adequately above the cut off level (500 mg/kg bw).

Toxicologic evaluations of DHA-rich algal oil in rats: Developmental toxicity study and 3-month dietary toxicity study with an in utero exposure phase

DHA-rich algal oil ONC-T18, tested for subchronic, reproductive, and developmental toxicity in the rat, did not produce any significant toxicologic manifestations. Based on the absence of maternal or developmental toxicity at any dosage level, a dosage level of 2000mg/kg/day was considered to be the no observed adverse-effect level (NOAEL) for maternal toxicity and embryo/fetal development when DHA-rich algal oil was administered orally by gavage to pregnant Crl:CD(SD) rats during gestation days 6–19. In a dietary combined one-generation/90-day reproductive toxicity study in rats, the NOAEL for F0 male and female and F1 male systemic toxicity was considered to be 50,000ppm (highest concentration administered) and 25,000ppm for F1 female systemic toxicity (higher mean body weight, body weight gain, and food consumption). F0 reproductive performance values, estrous cycle length, gestation length, or the process of parturition, and the numbers of former implantation sites and unaccounted-for sites were unaffected by algal oil exposure. Postnatal survival and developmental parameters in the F1 generation were unaffected by algal oil exposure at all dietary concentrations. There were no neurotoxic effects noted at any algal oil exposure level. The results support the safety of DHA-rich algal oil for its proposed use in food.

Scientific Opinion on Bisphenol A: evaluation of a study investigating its neurodevelopmental toxicity, review of recent scientific literature on its toxicity and advice on the Danish risk assessment of Bisphenol A

Bisphenol A (BPA) is used in the manufacture of plastics, to produce reusable drinking bottles, infant feeding bottles and other food storage containers. EFSA was asked to evaluate a dietary developmental neurotoxicity study in rats (Stump, 2009) and recent scientific literature (2007–2010) in terms of relevance for the risk assessment of BPA. The impact of these studies on the current Tolerable Daily Intake (TDI) of 0.05 mg BPA/kg body weight (b.w.)/day as set by EFSA in 2006 was assessed. Advice on the Danish risk assessment underlying the Danish ban of BPA in food contact materials for infants aged 0–3 years is included. Overall, based on this comprehensive evaluation of recent toxicity data, the Panel on food contact materials, enzymes, flavourings and processing aids (CEF) concluded that no new study could be identified, which would call for a revision of the current TDI. This TDI is based on the No-Observed-Adverse-Effect-Level (NOAEL) of 5 mg/kg b.w./day from a multi-generation reproductive toxicity study in rats, and the application of an uncertainty factor of 100. This factor is regarded as conservative based on all information on BPA toxicokinetics. The Panel noted that some studies conducted on developing animals have suggested other BPA-related effects of possible toxicological relevance, in particular biochemical changes in brain, immune-modulatory effects and enhanced susceptibility to breast tumours. These studies had several shortcomings. At present the relevance of these findings for human health cannot be assessed. Should any new relevant data become available in the future, the Panel will reconsider this opinion. A minority opinion is expressed by a Panel member and presented in an Annex to this opinion.

Ovarian Follicle Counts Using Proliferating Cell Nuclear Antigen (PCNA) and Semi-Automated Image Analysis in Rats

Ovarian follicle counting is a method to assess ovarian toxicity in reproductive toxicity studies in rats. Although ovarian follicle counting has been traditionally performed manually on hematoxylin and eosin (H&E)-stained sections, the use of immunohistochemical methods, including human cytochrome P450 1B1 (CYP1B1) and proliferating cell nuclear antigen (PCNA), have been used to enhance the visibility of the primordial and primary follicles to facilitate manual counting. In this study, serial sections from both ovaries from ten 3-month-old female Sprague Dawley rats were stained using routine H&E and immunohistochemistry for PCNA. Counting of primordial and primary follicles was performed manually using these two stains and by semi-automated image analysis of PCNA-stained slides. Although manual counting of PCNA-stained slides is preferable to manual counting of H&E-stained slides, manual counting involves variability between individual counters. Semi-automated image analysis of PCNA-stained slides yields an accurate and consistent count of these primordial/primary follicles and eliminates variability between individual counters.

Safety assessment of dietary diacylglycerol oil: A two-generation reproductive toxicity study in rats

Diacylglycerol (DAG) oil is a novel edible oil with similar taste and usability characteristics as conventional edible oils. Recent studies suggest that DAG oil may be helpful in the prevention and management of obesity. The objective of the present two-generation study was to evaluate potential adverse effects of DAG oil on reproductive processes. DAG oil was administered via gavage to rats (30/sex/group) for at least 70 days prior to mating, at dose levels of 0, 1.25, 2.5 or 5.0 ml/kg/day (0, 1160, 2320 and 4630 mg/kg/day). An additional group received a triacylglycerol (TAG) oil with a similar fatty acid composition to DAG oil. The rats were treated throughout the mating, gestation and lactation periods. Administration of DAG or TAG oil did not reveal any toxicologically significant effects on reproductive performance (mating, fertility and copulation/conception indices). DAG oil did not affect mean gestation lengths, the process of parturition, spermatogenic parameters, organ weights, histopathologic findings, mean numbers of pups born, implantation sites and unaccounted sites. F1 and F2 pup viability, live litter sizes, body weights, mean age of attainment of balanopreputial separation and vaginal patency were similar to those in the control group. Based on the results of this study, a dose level of 5.0 ml/kg (4630 mg/kg/day) was considered as the no-observed-adverse-effect level for reproductive and systemic toxicity, and neonatal toxicity.

Routes and Modes of Administration of Resorcinol and Their Relationship to Potential Manifestations of Thyroid Gland Toxicity in Animals and Man

Medical case reports published in the 20th century over the course of several decades show that resorcinol caused reversible adverse effects on the human thyroid gland (TG) manifested as hypothyroidism. Affected patients had ulcerating leg varicosities and underwent prolonged treatment with ointments containing high concentrations of resorcinol. In animal studies resorcinol failed to induce TG toxicity, unless pharmacokinetic/toxicokinetic (PK/TK) conditions were manipulated (e.g., injection of resorcinol in oil or application in a slow release formulation). A recently completed two-generation reproductive toxicity study in rats did not detect any adverse effects on either reproductive or TG end points (Welsch, Nemec, and Lawrence, 2008, Int. J. Toxicol. 37, this issue). Resorcinol intake via drinking water up to the palatability limit had resulted in average daily intakes (mg/kg) of 233 in F0 and F1 males and 304 (premating/gestation) or 660 (lactation) in females. Free resorcinol in blood plasma was barely detectable in a few parental animals, indicating rapid metabolism. This short review communication offers a perspective on compromised human skin barrier function as a likely cause of drastic increases in resorcinol absorption. In conjunction with multiple daily applications over many months to hyperemic, inflamed, and lesioned human skin much higher absorption was likely responsible for the reported human TG toxicity.

Safety studies on epigallocatechin gallate (EGCG) preparations. Part 3: Teratogenicity and reproductive toxicity studies in rats

Green tea and its principal active ingredient, epigallocatechin gallate (EGCG), have been demonstrated to have anticancer properties through interactions with multiple biochemical processes. Since these processes are often crucial in normal fetal development it is important to evaluate the potential effects of EGCG on the fetus. EGCG preparations of >91% purity were administered to pregnant rats during organogenesis and development in order to define the safety of Teavigo™, a high-concentration EGCG extract produced by the same novel method. In an initial preliminary study using subcutaneous and gavage routes, there was no evidence of any direct embryo–fetal toxicity, although some maternal toxicity was seen. In the main teratogenicity study, feeding pregnant rats diets supplemented at 1400, 4200 or 14,000 ppm during organogenesis was non-toxic to dams or fetuses. A two-generation study in rats fed 1200, 3600 or 12,000 ppm EGCG preparation showed no adverse effects on reproduction or fertility. The highest dose reduced the growth rate of offspring, and there was a slight increase in pup loss. A growth effect among pups was also seen at 3600 ppm, but in the second generation only. The lowest dose was considered the overall no-observed adverse effect level (NOAEL). As dams consumed twice the amount of feed during the crucial lactation period, the NOAEL was equivalent to 200 mg/kg/day EGCG preparation.

Enhanced one-generation reproductive toxicity study in rats for detecting endocrine-disrupting effects of chemicals

An enhanced one-generation reproductive toxicity study in rats without adjusting a litter size during the lactation period is proposed as a rapid and reliable bioassay for providing the data concerning adverse and/or low-dose effects of suspected endocrine disruptors. In this study, pregnant females are treated with the test substance from gestation day 0 through lactation day 21, in principle. F1 offspring from one-half of the litters in each dose group are killed and necropsied at weaning, while those from the remaining litters are examined for sexual maturation, estrous cyclicity, and/or sperm production. A series of pilot studies with ethynylestradiol as a reference chemical have suggested that the exposure of estrogenic chemicals during the early gestation period is critical for detecting effects on fertilization and/or implantation of eggs and survival of implants, and that expression of some genes including AR in the prostate and IGF-1 in the uterus of F1 offspring may be sensitive markers for monitoring potential estrogenic effects of the test compound.

Assessment in rats of the reproductive toxicity of gasoline from a gasoline vapor recovery unit

Gasoline (CAS 86290-81-5) is one of the world’s largest volume commercial products. Although numerous toxicology studies have been conducted, the potential for reproductive toxicity has not been directly assessed. Accordingly, a two-generation reproductive toxicity study in rats was conducted to provide base data for hazard assessment and risk characterization. The test material, vapor recovery unit gasoline (68514-15-8), is the volatile fraction of formulated gasoline and the material with which humans are most likely to come in contact. The study was of standard design. Exposures were by inhalation at target concentrations of 5000, 10 000, and 20 000 mg/m 3. The highest exposure concentration was approximately 50% of the lower explosive limit and several orders of magnitude above anticipated exposure during refueling. There were no treatment-related clinical or systemic effects in the parental animals, and no microscopic changes other than hyaline droplet nephropathy in the kidneys of the male rats. None of the reproductive parameters were affected, and there were no deleterious effects on offspring survival and growth. The potential for endocrine modulation was also assessed by analysis of sperm count and quality as well as time to onset of developmental landmarks. No toxicologically important differences were found. Therefore, the NOAEL for reproductive toxicity in this study was ≥20 000 mg/m 3. The only systemic effects, in the kidneys of the male rats, were consistent with an α−2 u-globulin-mediated process. This is a male rat-specific effect and not relevant to human health risk assessment.

Reproductive toxicity studies in rats with rimexolone, a corticoid ophthalmic suspension.

Rimexolone is a potent anti-inflammatory corticosteroid with a lower potential for elevating intraocular pressure, relative to other ophthalmic steroids, and is indicated for postsurgical inflammation and uveitis. Fertility and peri/postnatal toxicities were evaluated at oral gavage doses of 50, 150 or 500 mg/kg, and developmental toxicity at 100, 500, or 1000 mg/kg. In the fertility study, male rats were treated daily beginning 4 weeks prior to mating and females were treated daily beginning 2 weeks prior to mating, and through gestation day 6. Females were necropsied on gestation day 15 and males were necropsied after 10 weeks of exposure. In males, dose-related reductions in mean body weights, body weight gains, and food consumption occurred in all groups. In the 500 mg/kg females, mean body weights were reduced during gestation, and there was an increase in early resorptions and concomitant decrease in viable fetuses at this level. There were no effects on copulation or fertility indices, or on the number of corpora lutea and implantation sites. The no-observed-effect level (NOEL) for fertility and reproductive effects was 150 mg/kg. In the developmental toxicity study, female rats were treated daily from gestation days 6 through 17, necropsied on gestation day 20 and fetuses were evaluated. Maternal toxicity occurred at 500 and 1000 mg/kg as indicated by reduced maternal body weights and body weight gains. However, there was no indication of a developmental effect on fetuses due to rimexolone. The NOEL was 1000 mg/kg for the developing fetuses. In the peri/postnatal toxicity study, female rats were treated daily from gestation day 6 through lactation day 20 and necropsied. F1 developmental and behavioral parameters were evaluated. Selected F1 animals were mated at 12 weeks, allowed to deliver, and necropsied on lactation day 21. At 500 mg/kg, F0 maternal body weights were reduced during gestation and lactation, and F1 pup weights were reduced during lactation and the growth phase. There were no effects on the F1 fertility or reproductive capabilities, or on F2 developmental parameters. The NOEL for the F0 females and F1 offspring was 150 mg/kg. Together, these studies indicate that, unlike some corticosteroids, rimexolone does not produce developmental or reproductive toxicity in rats.

Preclinical safety evaluation of cerivastatin, a novel HMG-CoA reductase inhibitor

Cerivastatin is a new but structurally distinct 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (“statin”). It effectively decreases low-density lipoprotein (LDL) cholesterol at 1% of the doses of other currently available statins. The toxicology of cerivastatin was evaluated in a comprehensive program of studies including: (1) single- and multiple-dose toxicity studies in rats, mice, minipigs, dogs, and monkeys; (2) reproductive toxicity studies in rats and rabbits; (3) in vitro and in vivo mutagenicity assays in rats and mice; and (4) carcinogenicity studies in rats and mice. In addition, studies were undertaken to investigate the effects of cerivastatin on lens opacity, testicular tissue, and hemorrhage in dogs. Oral administration of single and multiple doses of cerivastatin over periods ranging from 4 weeks to 24 months was generally well tolerated. Adverse effects were similar to those observed with other statins and primarily involved the liver and muscle tissue. At the high doses used in the toxicologic studies, cerivastatin caused elevations in serum transaminases and creatine phosphokinase levels as well as some degeneration of muscle fibers in rats, mice, dogs, and minipigs. In dogs, the species most sensitive to statins, cerivastatin caused erosions and hemorrhages in the gastrointestinal tract, bleeding in the brain stem with fibroid degeneration of vessel walls in the choroid plexus, and lens opacity. Apart from minor morphologic changes in the testicular tissue of dogs—the only organ for which a comparably low margin of safety was observed—cerivastatin had no significant effects on the male or female reproductive system. Cerivastatin also caused no primary embryo-toxic or teratogenic effects. With the exception of cerivastatin-induced effects on the eyes and testicles, administration of mevalonic acid reversed the toxicologic effects of cerivastatin, indicating that the toxic effects were related to its mode of action and not to any intrinsic toxicity of the molecule itself. There was no evidence that cerivastatin had any mutagenic effects and, in contrast to other statins, high doses of cerivastatin did not induce tumors in rats. The main metabolite of cerivastatin was well tolerated systemically in all animals, including dogs. Overall, cerivastatin has a similar toxicologic profile to other statins and is a well-tolerated HMG-CoA reductase inhibitor.

Japan Pharmaceutical Manufacturers Association (JPMA) Survey on Background Control Data of Developmental and Reproductive Toxicity Studies in Rats, Rabbits and Mice

ABSTRACT The Non‐Clinical Evaluation Subcommittee of the Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA) collected historical control data from developmental and reproductive toxicity studies, which were conducted by the member companies and associated contract laboratories between 1986 and 1993. The data include spontaneous incidences of fetal morphological alterations and other observations made at terminal cesarean sections in rats, rabbits and mice. In addition, mating and natural delivery data in rats are also provided. There were strain differences as well as inter‐laboratory variations in the incidences of fetal visceral and skeletal alterations for both rats and rabbits. These inter‐laboratory variations were attributed to differences in the selection of observation parameters, observation criteria and classification of the findings.

Toxicokinetic analysis of losartan during gestation and lactation in the rat.

Previous developmental and reproductive toxicity studies in rats with losartan, a potent AT1-selective angiotensin II (AII) receptor antagonist, correlated maternal treatment during gestation day (GD) 15-20 with irreversible renal abnormalities in the F1 generation (Spence et al., '95a,b). Continued treatment through lactation was also associated with increases in pup mortality and decreases in pup body weights that persisted through weaning. The studies presented here were undertaken to quantify fetal and neonatal exposure to losartan when administered to the dam by oral gavage during early gestation, late gestation, and lactation. Following daily oral dosing of 135 mg/kg/day on GD6-15, fetal drug levels were negligible. However, losartan and its active metabolite, EXP3174 (L-158,641) were readily detectable in fetal plasma on GD 20 (estimated AUC values, 50.70 and 167.70 micrograms/hr/ml, respectively) and maternal milk during lactation (1.61 and 1.67 micrograms/ml, respectively). These studies suggest that the relative increased sensitivity of the fetus as compared to the neonate for losartan-induced renal lesions is related to the degree of exposure which is dependent on the time of administration (early gestation vs. late gestation/lactation) and the route of exposure (transplacental or through the milk). Furthermore, the maximum exposure to losartan and EXP3174 correlates with the ontogeny of the renin angiotensin system on approximately GD 17 and the critical period for losartan-induced renal lesions (GD15-20). The data support the hypothesis that the observed adverse fetal and neonatal effects are pharmacologically mediated, presumably through the lack of AT1 receptor stimulation.

Symposium on estrogens in the environment, III.

Symposium on estrogens in the environment, III.

Preclinical Toxicology and Safety Pharmacology of Brodimoprim in Comparison to Trimethoprim and Analogs

The toxicology and safety pharmacology of brodimoprim (Ro 10-5970), a new dihydrofolate reductase inhibitor for antimicrobial chemotherapy, are reported. The toxicity is compared to trimethoprim and other dihydrofolate reductase inhibitors of the trimethoprim type. In safety pharmacological tests brodimoprim showed no significant activity in the cardiovascular, autonomic neuroeffector or central nervous systems. Effects on urine volume and sodium and potassium excretion were not noted. The acute toxicity of brodimoprim after oral administration is low. In repeated dose studies in rats, oral doses up to 50 mg/kg/day were generally well tolerated. In the baboon no toxic effects were seen even at repeated doses up to 150 mg/kg/day; on the other hand the dog was found to be particularly sensitive to treatment as 20 mg/kg/day were poorly tolerated. Target organ systems included central nervous system, liver, red blood cell parameters and thyroid gland. Doses up to 100 mg/kg/day were not teratogenic or embryotoxic in rabbits. However, treatment with 100 mg/kg/day in reproductive toxicity studies in rats induced effects on fetal/litter weight, survival of offspring and litter size and increased the incidence of skeletal variations and malformed offspring. No mutagenicity was found in the tests performed with brodimoprim. In comparison brodimoprim shows the typical toxicity known for trimethoprim and analogs. In pyrimethamine toxic effects occurred at considerably lower doses than in the other compared compounds.