Evaluation of the developmental toxicity of diallyl phthalate administered orally to rats

The objective of this study was to evaluate the developmental toxic potential of diallyl phthalate (DAP) in rats. Pregnant Sprague-Dawley rats were given DAP at doses of 0 (olive oil), 100, 150, 200, and 250 mg/kg/day, by gavage (5 ml/kg), on Gestational Days (GD) 6 through 20. Gross examination at necropsy revealed liver lesions in dams given 150 mg/kg/day or higher doses. In addition, maternal weight gain and food consumption were significantly reduced at 200 and 250 mg/kg/day. There was no significant increase in the incidence of resorptions, or malformations, at any dose. Fetal body weight was significantly reduced at 200 and 250 mg/kg/day. There was a significant increase in the incidence of fetuses with skeletal variations at 250 mg/kg/day. Retarded ossification of certain bones (i.e. forelimb and hindlimb phalanges, metatarsals, and caudal vertebrae) was also observed. There was no sign of developmental toxicity at 100 and 150 mg/kg/day.

Thus, DAP caused fetal toxicity at doses which also produced maternal effects, but no embryolethality or teratogenicity.     

氟他胺对仔鼠雄性生殖系统的影响

目的探讨宫内暴露氟他胺对雄性仔鼠生殖系统的影响。方法孕鼠随机分为5个实验组及一个对照组,从孕12~17d连续6d实验组每天腹部皮下注射用生理盐水配制的氟他胺4492.2、4882.8、5273.4、5664.0、6054.6μg/kg,对照组注射同量生理盐水;于怀孕20d行剖宫术,提取雄性仔鼠睾丸,做电镜检测;并于出生后第2、13、28d观察雄性仔鼠性分化与性发育的指标。结果染毒组雄性子代肛殖距除4492.2μg/kg剂量外,其余各组均明显小于对照组(P<0.01);尿道下裂的发生率依次为0、29.00%、63.68%、93.02%、100%;单侧隐睾发生率分别为0、4.55%、8.70%、13.95%、15.56%;乳晕延迟退化率均为100%;各组前列腺不发育或发育不全。电镜检测的结果表明睾酮生成的细胞器受损。结论宫内暴露于氟他胺可使雄性仔鼠性分化与性发育异常。     

Hazard to the developing male reproductive system from cumulative exposure to phthalate esters—dibutyl phthalate,diisobutyl phthalate,butylbenzyl phthalate,diethylhexyl phthalate,dipentyl phthalate,and diisononyl phthalate

Phthalate esters are found in a wide variety of consumer and food packing products. Hence there is widespread exposure of the human population to these chemicals. Some of the phthalate esters are known to be toxic to the developing male reproductive system. This paper derives a reference dose (RfD) for each of the phthalate esters (dibutyl phthalate, diisobutyl phthalate, butylbenzyl phthalate, diethylhexyl phthalate, dipentyl phthalate, and diisononyl phthalate) that cause these effects. As these phthalate esters cause similar adverse biological effects and have the same mechanism of action, it is appropriate in a risk assessment to consider the potential adverse effects from cumulative exposure to these chemicals using a dose addition model. This paper provides examples of a cumulative risk assessment using the hazard index and relative potency approaches from the RfDs derived from studies in laboratory animals and exposure information in people. The results of the cumulative risk assessments for both a US and a German population show that the hazard index is below one. Thus it is unlikely that humans are suffering adverse developmental effects from current environmental exposure to these phthalate esters.     

Adverse effects of butyl benzyl phthalate on the reproductive and hematopoietic systems of male rats

A 14-day dietary study was conducted in adult, male, Fischer 344 rats at levels of 0.0, 0.625, 1.25, 2.5 and 5.0% butyl benzyl phthalate (BBP) to evaluate potential effects of this plasticizer on the male reproductive and hematopoietic systems. Total body, thymus, testis, epididymis, prostate and seminal vesicle weights were reduced in the 2.5% and 5% BBP dose groups, while pituitary weight was unaffected. Histological evaluations revealed dose-dependent atrophy of the testis, prostate and seminal vesicles at 2.5% and 5%, atrophy of the thymus and epididymis at 5%, and the presence of immature sperm cells in the tubular lumens and necrosis of the tubular epithelium in the epididymis at 2.5% and 5% BBP. Plasma testosterone concentration was decreased at 5%, while follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations were increased at 2.5% and 5.0% BBP. The circulating components of blood, and clotting times (prothrombin time, activated partial thromboplastin time), were unaffected although bone marrow cellularity was reduced at 2.5% and 5%. Changes in non-reproductive organs included enlargement of liver and kidneys, thymic atrophy and associated morphological abnormalities in these organs. These data indicate a direct toxic effect of BBP on the testis with secondary effects on other reproductive organs. Pituitary and hypothalamic responses did not appear to be affected. The reduced bone marrow cellularities suggest that prolonged exposures to BBP could affect circulating blood components or compromise clotting ability.     

Dose-dependent alterations in androgen-regulated male reproductive development in rats exposed to Di(n-butyl) phthalate during late gestation.

Di(n-butyl) phthalate (DBP) is a commercially important plasticizer and ubiquitous environmental contaminant. Since previous, limited dose-response studies with DBP that reported alterations in male reproductive development and function failed to establish a NOAEL (no-observed-adverse-effect level), an extensive dose-response study was conducted. Pregnant CD rats were given DBP by gavage at 0, 0.5, 5, 50, or 100 mg/kg/day (n = 19-20) or 500 mg/kg/day (n = 11) from gestation day 12 to 21. In male offspring, anogenital distance was decreased at 500 mg DBP/kg/day. Retained areolas or nipples were present in 31 and 90% of male pups at 100 and 500 mg/kg/day, respectively. Preputial separation was not delayed by DBP treatment in males with normal external genitalia, but cleft penis (hypospadias) was observed in 5/58 rats (4/11 litters) at 500 mg/kg/day. Absent or partially developed epididymis (23/58 rats in 9/11 litters), vas deferens (16/58 animals in 9/11 litters), seminal vesicles (4/58 rats in 4/11 litters), and ventral prostate (1/58 animals) occurred at 500 mg/kg/day. In 110-day-old F(1) males, the weights of the testis, epididymis, dorsolateral and ventral prostates, seminal vesicles, and levator ani-bulbocavernosus muscle were decreased at 500 mg/kg/day. At 500 mg/kg/day, widespread seminiferous tubule degeneration was seen in 25/58 rats (in 9/11 litters), focal interstitial cell hyperplasia in 14/58 rats (in 5/11 litters), and interstitial cell adenoma in 1/58 rats (in 1/11 litters). For this 10-day prenatal (embryonic and fetal) exposure to DBP, the NOAEL and LOAEL (lowest-observed-adverse-effect level) were 50 and 100 mg/kg/day, respectively. This is currently the lowest NOAEL described for the toxicity of DBP.     

Effects of in utero exposure to finasteride on androgen-dependent reproductive development in the male rat.

Finasteride is a specific inhibitor of type II 5alpha-reductase, the enzyme that converts testosterone (T) to the more potent androgen receptor agonist dihydrotestosterone (DHT). In utero exposure to androgen receptor antagonists and T biosynthesis inhibitors have induced permanent effects on androgen-sensitive end points such as anogenital distance (AGD), nipple retention, and malformations of the male rat reproductive tract. The objectives of this study were to (1) characterize the dose response of finasteride-mediated alterations in androgen-dependent developmental end points, (2) determine whether prenatal exposure to finasteride permanently decreases AGD or results in nipple retention, and (3) evaluate whether AGD or nipple retention is predictive of adverse alterations in the male reproductive tract. Pregnant Crl:CD(SD)BR rats (n=5-6/group) were gavaged with either vehicle or finasteride at 0.01, 0.1, 1.0, 10, or 100 mg/kg/day on gestation days 12 to 21. All male offspring were monitored individually until necropsy on postnatal day (PND) 90. The present study design has been used previously for other antiandrogens and is sensitive to perturbations of the male rat reproductive tract. Decreases in AGD on PND 1 and increases in areolae-nipple retention on PND 13 were significantly different from controls in all finasteride-exposed male rats. Finasteride-induced changes in AGD and nipple retention were permanent in male rats exposed to finasteride at and above 0.1 mg/kg/day. On PND 90, dorsolateral and ventral prostate lobes were absent in 21 to 24% of rats exposed to 100 mg/kg/day finasteride and weighed significantly less at and above 10 mg/kg/day. In the highest dose group, 73% of animals had ectopic testes, much higher than previously reported. The most sensitive malformation other than decreased AGD and nipple retention was the dose-dependent increase in hypospadias. The lowest observed adverse effect level (LOAEL) for finasteride-induced permanent effects in this study was 0.1 mg/kg/day based on permanent changes in AGD and nipple retention. Finasteride-induced changes in AGD and retention of nipples were highly predictive of hypospadias, ectopic testes, and prostate malformations even though some animals with retained nipples or decreased AGD may not have had other reproductive tract malformations. In summary, prenatal exposure to finasteride specifically inhibited DHT-mediated development with little to no change in T-mediated development.     

Effect of lindane on CYP‐mediated steroid hormone metabolism in male mice following in utero exposure

A wide number of pesticides, including highly persistent organochlorinated compounds, such as lindane (LIN), may induce reproductive and developmental alterations by directly binding to the estrogen/androgen receptors or altering steroid hormone metabolism. In the present work, we have investigated whether LIN in utero exposure of CD1 mice affects the reproductive system in male offspring by causing an impairment of the CYP‐dependent steroid hormone metabolism. Dam exposure to 25 mg kg^?1 b.w. LIN occurred during critical developmental periods, from gestational days 9 to 16. Effects on hepatic CYP‐mediated testosterone (TST) hydroxylase, aromatase activities and testicular parameters were tested at postnatal days (PND 50, 65–69, 100) that are critical for sexual maturation in CD1 mice. In the adult F1 mice significant changes of male reproductive endpoints (testis weight, spermatid number) as well as dramatic effects on CYP‐mediated TST metabolism were observed on PND 65–69, in the absence of any of systemic toxicity. The levels of TST 6β‐ and 2α‐hydroxylation and dehydrogenation showed the highest level of reduction, suggesting CYP 3A and 2C families as the major target of LIN induced effects. All changes were almost recovered on PND 100. No effects on aromatase activity were evidenced. Overall, these findings provide useful information for a better characterization of the LIN mode of action. They suggest that LIN‐induced toxicity in males is linked to an impairment of steroid hormone homeostasis, due to CYP‐mediated TST catabolism modulation and differs from LIN receptor‐mediated mechanism previously reported in females. Copyright © 2009 John Wiley & Sons, Ltd.     

Cumulative effects of dibutyl phthalate and diethylhexyl phthalate on male rat reproductive tract development: altered fetal steroid hormones and genes.

Exposure to plasticizers di(n-butyl) phthalate (DBP) and diethylhexyl phthalate (DEHP) during sexual differentiation causes male reproductive tract malformations in rats and rabbits. In the fetal male rat, these two phthalate esters decrease testosterone (T) production and insulin-like peptide 3 (insl3) gene expression, a hormone critical for gubernacular ligament development. We hypothesized that coadministered DBP and DEHP would act in a cumulative dose-additive fashion to induce reproductive malformations, inhibit fetal steroid hormone production, and suppress the expression of insl3 and genes responsible for steroid production. Pregnant Sprague Dawley rats were gavaged on gestation days (GD) 14-18 with vehicle control, 500 mg/kg DBP, 500 mg/kg DEHP, or a combination of DBP and DEHP (500 mg/kg each chemical; DBP+DEHP); the dose of each individual phthalate was one-half of the effective dose predicted to cause a 50% incidence of epididymal agenesis. In experiment one, adult male offspring were necropsied, and reproductive malformations and androgen-dependent organ weights were recorded. In experiment two, GD18 testes were incubated for T production and processed for gene expression by quantitative real-time PCR. The DBP+DEHP dose increased the incidence of many reproductive malformations by >or=50%, including epididymal agenesis, and reduced androgen-dependent organ weights in cumulative, dose-additive manner. Fetal T and expression of insl3 and cyp11a were cumulatively decreased by the DBP+DEHP dose. These data indicate that individual phthalates with a similar mechanism of action, but with different active metabolites (monobutyl phthalate versus monoethylhexyl phthalate), can elicit dose-additive effects when administered as a mixture.     

Adult 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure and effects on male reproductive organs in three differentially TCDD-susceptible rat lines.

The contribution of genetic factors to adult male reproductive system toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was analyzed in three rat lines differentially resistant to TCDD acute lethality: line A, B, and C rats (selectively bred from TCDD-resistant Han/Wistar [Kuopio; H/W] and TCDD-sensitive Long-Evans [Turku/AB; L-E] rats). The resistance is linked to a mutated H/W-type aryl hydrocarbon receptor allele in line A and to an H/W-type unknown "B" allele in line B. Line C rats do not have resistance alleles. Mature male line A, B and C rats were given single oral doses up to 1000, 300, and 30 micrograms/kg TCDD, respectively. The dose-responses of TCDD effects on male reproductive organ weights, sperm numbers, and serum testosterone concentrations were analyzed 17 days after exposure. Serum testosterone concentrations were decreased by the highest doses of TCDD, and there were no major sensitivity differences among the rat lines. Correspondingly, the decrease in relative weight of ventral prostate and seminal vesicles was seen only after a dose of >/=100 micrograms/kg TCDD. Thus the effect was observed only in resistant lines A and B. The relative weights of testes and epididymides were not affected. Significant decrease in spermatogenesis was observed in each rat line, but the amount of decrease was reduced by resistance alleles. The highest TCDD dose decreased the daily sperm production by 37, 38, and 60% in line A, B, and C rats, respectively. Therefore, the resistance alleles appear to selectively modify the TCDD effects on the adult male reproductive system. The fact that the influence of resistance alleles on spermatogenesis is different from that on androgenic status indicates that the effect of TCDD on sperm numbers is not fully related to decreased serum testosterone.     

Evaluation of effects of prenatal exposure to the cyanide and thiocyanate in wistar rats

A study was performed at term and at weaning to verify the toxic effects of the prenatal exposure to potassium cyanide (KCN) and potassium thiocyanate (KSCN) in pregnant Wistar rats. Females received daily in drinking water the doses: 1, 3 and 30 mg KCN/kg or 0.8, 2.4 and 24 mg KSCN/kg from GD 6 to GD 20 and were euthanized on GD 20 (trial A) or one day after weaning (trial B). Skeletal and visceral analyses of the fetuses (trial A) were performed and samples of blood and different organs, from both dams (trials A and B) and weaned pups (trial B), were collected in order to perform the biochemical evaluation and histopathology. Results showed high thiocyanate levels in dams of the different experimental groups from both trials. The intensity of the histological lesions observed in dams of trial B was similar to that of trial A, except those lesions found in the pancreas. The histopathological study of this organ revealed loss of cells in the Islets of Langerhans from dams of trial A which received the highest dose of cyanide (CN). There was an increase in the number of biliary ducts in animals treated with the highest doses of both thiocyanate and cyanide. The histopathological study of the spleen and the lungs of experimental and control groups did not reveal any significant alteration. In relation to fetuses (trial A), the visceral and skeletal evaluations did not reveal any significant malformation; on the other hand, pups from trial B showed some histological alterations similar to those observed in their dams. It is concluded that the cyanide and/or thiocyanate promoted toxic effects in the fetuses some of which could also be observed at weaning.     

Effect of in utero and lactational exposure of triazophos on reproductive system functions in male offsprings,Rattus norvegicus

In the present study, Triazophos (TZ) was used at acceptable daily intake (ADI) to investigate the consequence of prenatal and postnatal exposure on reproductive functions in the male offsprings. Pregnant females were divided into three groups, the first group was orally gavaged with olive oil (control), the second group was administered with 0.01?mg kg^?1 bw of the ADI of TZ from gestation day (GD) 1 until parturition (designated as P group) and the third group was gavaged with the same dose from GD1 to postnatal day (PND) 21 of lactation (marked as P?+?L group). Non-significant reduction occurred in the body weight of pups except at (PND) 35 during which body weight of P?+?L group pups significantly decreased. Male offsprings born to TZ exposed females showed significant changes at maturity (PND 63) in weight of liver, thyroid and testis, alterations in the levels of protein, urea, creatinine in plasma and abnormal levels of cholesterol, phospholipids and lipid peroxidation in testicular homogenate. Gonadal inhibition in TZ exposed progeny was reflected from a significant fall in sperm count, sperm motility, plasma testosterone level and histopathological alterations in testis. Hence, in utero and lactational exposure to ADI level of TZ influences testis development and functions in the male offsprings. Further investigations are suggested with germline studies of offsprings to examine the transgenerational effect of TZ exposure.     

Toxicological review of male reproductive effects and trichloroethylene exposure: assessing the relevance to human male reproductive health

Effects of trichloroethylene (TCE) on male reproduction and fertility have been studied in mice and rats, and assessed in workers exposed to TCE. Only limited evidence exists for any male reproductive effects in rats or humans. The human studies of TCE male reproductive effects failed to provide much useful information for risk assessment. First, the TCE-specific studies are limited in group size, scope, and typically provide no data on dose, so dose–response assessment is impossible. In other studies, TCE is only one of many solvents identified in the workplace, such that the confounding exposures or lack of evidence of specific exposures make the exposure assessment useless. For TCE risk assessment, one currently must rely upon animal studies as more reliable and useful. The rat studies were generally negative, showing systemic toxicity but little or no male reproductive toxicity. The mouse studies showed various organ effects in the male reproductive system and were typically associated with increased liver weight and kidney toxicity. Enzyme induction and oxidative metabolism appear to be important in the systemic toxicity and may likewise play a role in the reproductive toxicity of TCE. Oxidative metabolites of TCE are formed in the mouse epididymis resulting in epididymal damage, and at systemically toxic high doses, TCE may adversely affect the maturation of sperm and decreasing sperm motility. Protection against systemic toxicity should also protect against adverse effects including male reproductive toxicity.     

MDMA (ecstasy) delays pubertal development and alters sperm quality after developmental exposure in the rat

3,4-Methylenedioxymethamphetamine, MDMA or “ecstasy” is consumed mainly by young population at childbearing age. Therefore, there may be a risk of exposure of some pregnant women. The effects of the developmental exposure to MDMA on the sexual development and long-term sexual behaviour/fertility were assessed in Sprague–Dawley rats. MDMA was administered subcutaneously at 0 (control), 0.5, 5 and 10 mg/kg to female rats once a day, three consecutive days a week during 10 weeks, including gestation and lactation. The male offspring was evaluated for sexual maturation and mated with untreated sexually receptive females to evaluate the mating and pregnancy rates. Hormonal, haematological, biochemical, histological, genotoxicological and testicular and sperm parameters were also evaluated. A significant higher incidence of DNA damage in sperm and interstitial oedema in testes was found. There was also a significant and dose-related decrease in sperm count and a significant decrease in sperm motility at all doses. A significant delay in preputial separation onset in all treated groups was observed. This study reports by the first time an alteration of spermatogenesis after in utero and lactation MDMA exposure in the rat.     

Effects of in utero exposure to the organophosphate insecticide fenitrothion on androgen-dependent reproductive development in the Crl:CD(SD)BR rat.

Fenitrothion [0,0-dimethyl-O-(4-nitro-m-tolyl) phosphorothioate] is an organophosphate insecticide that has been shown to have antiandrogenic activity using in vitro and in vivo screening assays. Studies were performed to evaluate the ability of fenitrothion to disrupt androgen-dependent sexual differentiation in the male rat. Pregnant Crl:CD(SD)BR rats were administered fenitrothion by gavage at 0, 5, 10, 15, 20, or 25 mg/kg/day ( n = 6-11/group) from gestation day (GD) 12 to 21. Maternal toxicity was observed in the dams treated with 20 and 25 mg fenitrothion/kg/day based on muscle tremors and decreases in body weight gain from GD 12 to 21. Fetal death was increased in the 20 and 25 mg/kg/day exposure groups, as evidenced by a decrease in the proportion of pups born alive. Androgen-mediated development of the reproductive tract was altered in male offspring exposed in utero to maternally toxic levels of fenitrothion (25 mg/kg/day), as evidenced by reduction in anogenital distance on postnatal day (PND) 1 and retention of areolae on PND 13. However, these effects were only transient, and there were no indications of abnormal phenotypes or development of androgen-dependent tissues on PND 100. At the dose levels evaluated in this study, fenitrothion was only weakly antiandrogenic in vivo compared with other androgen receptor antagonists such as flutamide, linuron, and vinclozolin. Based on observed fetotoxicity at 20 mg/kg/day, the lowest observed adverse effect level (LOAEL) for developmental effects can be lowered from 25 to 20 mg/kg/day.     

In utero and lactation exposure of rats to 1R4F reference cigarette mainstream smoke: effect on prenatal and postnatal development.

Childhood cognitive and behavioral deficits have been reported in children born to mothers who smoked during pregnancy (Institute of Medicine, 2001). To investigate these potential responses in an animal model, reproductive and neurotoxicity evaluations based on the U.S. FDA guidelines were used to examine the offspring of male and female Sprague-Dawley rats exposed 2 h/day, 7 days/week by nose-only inhalation to whole mainstream smoke total particulate matter (TPM). Concentrations of 150, 300, or 600 mg/m(3) were used (males: 4 weeks prior to and during mating; and females: 2 weeks prior to mating, during mating, and through weaning at postnatal day 21). Sham air controls receiving filtered air and cage controls were also maintained. F(1) rats were weighed, identified by gender, examined for clinical signs of toxicity, and evaluated for neurobehavioral effects through postnatal day 65. Parental exposure was evidenced by smoke concentration-related increases in blood carboxyhemoglobin, nicotine, and cotinine and by characteristic cigarette smoke-related rodent respiratory tract histopathology. Also, nicotine and cotinine were found in F(1) blood through the lactation period. Maternal toxicity occurred at concentrations of 300 and 600 mg TPM/m(3), where total body weight gain during gestation was significantly (p < or = 0.05) decreased compared to sham controls. While smoke concentration-related decreases in F(1) birth weight and growth were evident (600 mg TPM/m(3), significantly different from sham at all time points), no adverse effects on developmental landmarks, including age at vaginal patency or preputial separation, motor activity, acoustic startle response or learning, and memory, were observed in the F(1) generation. This study confirmed that maternal exposure to high levels of mainstream cigarette smoke during gestation and lactation reduces birth weight and retards growth in the rat neonate; however, the developmental and neurobehavioral testing methodologies employed did not appear to be sensitive for an evaluation of neonatal behavioral effects following parental smoke exposure.     

A dose response study following in utero and lactational exposure to di-(2-ethylhexyl) phthalate (DEHP): reproductive effects on adult male offspring rats

The reproductive effects of in utero and lactational exposure to di-(2-ethylhexyl) phthalate (DEHP) in adult male offspring rats were investigated. The selected endpoints included reproductive organ weights, testicular function, hormonal status, sexual behaviour and fertility. Two wide ranges of doses, low and high, were tested. Female Wistar rats were treated daily with DEHP and peanut oil (vehicle control) by gavage from gestation day 6 to lactation day 21. The low-doses were 0.015, 0.045, 0.135, 0.405 and 1.215 mg DEHP/kg body weight (bw)/day, and the high-doses were 5, 15, 45, 135 and 405 mg DEHP/kg bw/day. A reduction in daily sperm production of 19-25% in relation to control was observed in animals exposed to 15, 45, 135 and 405 mg/kg/day. Quantitation of specific cell types shows that the observed effects in daily sperm production are not related to changes in the number of Sertoli cells or their capability to support early stages spermatocytes. A low incidence of cryptorchidism was observed in DEHP exposed groups with a lowest observed adverse effect level of 5mg/kg/day. Serum testosterone concentration was similar to control at most doses but was significantly increased at 0.045, 0.405 and 405 mg DEHP/kg/day. In spite of this effect, the weight of seminal vesicle with coagulating glands was significantly reduced at 405 mg/kg/day. Testis, epididymis and prostate weights were similar among groups. Fertility and sexual behaviour were not affected by DEHP treatment at any dose. Overall, our results show that in utero and lactational DEHP exposure reduces daily sperm production and has the potential to induce reproductive tract abnormalities (of which cryptorchidism seems to be the most sensitive in our rat strain) in male offspring rats. The lowest observed adverse effect levels (LOAELs) for these effects were 15 and 5 mg/kg/day, respectively. Therefore, the no observed adverse effect level (NOAEL) for this study can be set at 1.215 mg/kg/day.     

Effects of perinatal loratadine exposure on male rat reproductive organ development

Normal pre- and postnatal male reproductive development and function is dependent upon testicular androgen production and is sensitive to antiandrogenic perturbations. It was of interest to determine if the H₁ histamine antagonist loratadine had the potential to alter androgen-mediated reproductive development in the rat, a sensitive species for detecting antiandrogenic effects. Loratadine was administered orally by gavage to pregnant Sprague–Dawley rats at doses of 4, 12 or 24 mg/kg from gestation day 7 to postnatal day 4, encompassing the period of androgen-dependent male reproductive development. Vehicle control rats received 0.4% aqueous methylcellulose. Dams were allowed to deliver naturally and rear their offspring until postnatal day 21. On postnatal day 21 male offspring were retained for further evaluation of androgen-dependent endpoints and the female offspring were euthanized and their sex confirmed internally. Males were necropsied from postnatal day 72 to 85. Dams administered 24 mg/kg of loratadine exhibited a transient 45% decrement in maternal body weight gain at the initiation of dosing (gestation days 7–9). Mean pup body weight on postnatal days 1 and 4 were approximately 4% lower than controls. No other effects on offspring growth were observed. Anogenital distance on postnatal day 1 was unaffected by loratadine exposure. Loratadine exposure did not induce the retention of nipples in male rats, affect preputial separation, or induce external malformations, including hypospadias. Seminal vesicle and prostate weights were not decreased by loratadine exposure. These data clearly demonstrate that systemic loratadine exposure, in multiples up to 26 times clinical exposure levels, does not exhibit in vivo antiandrogen activity, as evidenced by the absence of alterations or malformations in androgen-dependent reproductive tissues in male rats exposed to loratadine during the critical period of androgen-dependent development.     

Use of the Adverse Outcome Pathway (AOP) framework to evaluate species concordance and human relevance of Dibutyl phthalate (DBP)-induced male reproductive toxicity

Dibutyl phthalate (DBP) is a phthalate ester used as a plasticizer, and solvent. Studies using rats consistently report that DBP exposure disrupts normal development of the male reproductive system in part via inhibition of androgen synthesis. However, studies using xenograft models report that in human fetal testis DBP exposure is unlikely to impair testosterone synthesis. These results question the validity of the rat model for assessment of male reproductive effects caused by DBP. The Adverse Outcome Pathway (AOP) framework was used to evaluate the available evidence for DBP-induced toxicity to the male reproductive system. Three relevant biological elements were identified: 1) fetal rats are more sensitive than other rodents and human fetal xenografts to DBP-induced anti-androgenic effects, 2) DBP-induced androgen-independent adverse outcomes are conserved amongst different mammalian models and human fetal testis xenografts, and 3) DBP-induced anti-androgenic effects are conserved in different mammalian species when exposure occurs during postnatal life stages.     

Studies on the prenatal toxicity of toluene in rabbits following inhalation exposure and proposal of a pregnancy guidance value

Prenatal toxicity of toluene was determined in two separate studies by inhalation exposure of Himalayan rabbits. In the first study 15 artificially inseminated females per group were exposed to 30, 100, or 300 ppm and in the second study 20 artificially inseminated females per group inhaled 100 or 500 ppm. In each case the rabbits were exposed for 6 hours per day from day 6 post-insemination (p. i.) to day 18 p. i. The respective controls inhaled conditioned clean air under the same exposure conditions. No signs of maternal toxicity were observed. All data obtained on gestational parameters were found to be within the variation range reported for this rabbit strain. The fetal external, soft tissue and skeletal findings were seen in toluene exposed fetuses in a frequency similar to the corresponding and/or historical controls. Differences observed between the groups were not concentration dependent and were considered incidental rather than compound related. Therefore, toluene was not embryotoxic, fetotoxic, or teratogenic for rabbits exposed during the period of organogenesis. The highest concentration tested under these conditions (500 ppm) was found to be a no-observable-adverse-effect level (NOAEL) for both the adult and the fetal Himalayan rabbit. Based on these and previous results of animal studies of prenatal toxicity, a safety or uncertainty factor approach is considered for setting limits of exposure for women at workplaces. A pregnancy guidance value of 20 ppm is proposed.The present studies were sponsored by the Berufsgenossenschaft der Chemischen Industrie, W-6900 Heidelberg, FRG