Effects of prenatal perfluorooctane sulfonate (PFOS) exposure on lung maturation in the perinatal rat

BACKGROUND: Perfluorooctane sulfonate (PFOS), found widely in wildlife and humans, is environmentally and metabolically stable. Environmental PFOS may be from its use as a surfactant, hydrolysis of perfluorooctanesulfonyl fluoride, and degradation of N-alkyl-perfluorooctanesulfonamide compounds formerly used in numerous applications. Prenatal exposure to PFOS in rodents causes neonatal mortality; treatment on gestation days (GD) 19-20 is sufficient to induce neonatal death in rats. Affected pups are born alive but present with labored breathing. Their lungs are pale and often do not expand fully on perfusion. METHODS: Pregnant Sprague-Dawley rats received 0, 25, or 50 mg/kg/day PFOS/K+ orally on GD 19-20. Lungs from GD 21 fetuses and neonates were prepared for histology and morphometry. Rescue experiments included co-administration of dexamethasone or retinyl palmitate with PFOS. Pulmonary surfactant was investigated with mass spectrometry in GD 21 amniotic fluid and neonatal lungs. Microarray analysis was carried out on PND 0 lungs. RESULTS: Histologically, alveolar walls were thicker in lungs of PFOS-exposed newborns compared to controls. The ratio of solid tissue:small airway was increased, suggesting immaturity. Rescue studies were ineffective. Phospholipid concentrations and molecular speciation were unaffected by PFOS. No changes in markers of alveolar differentiation were detected by microarray analysis. CONCLUSIONS: Morphometric changes in lungs of PFOS exposed neonates were suggestive of immaturity, but the failure of rescue agents and normal pulmonary surfactant profile indicate that the labored respiration and mortality observed in PFOS-treated neonates was not due to lung immaturity.     

Developmental toxicity evaluation of butylparaben in Sprague-Dawley rats

The developmental toxicity potential of butylparaben (CAS No. 94-26-8) was evaluated in rats. Sprague-Dawley rats were administered butylparaben in 0.5% carboxymethylcellulose by oral gavage at dose levels of 0, 10, 100, or 1,000 mg/kg/day on gestation days (GD) 6-19 (sperm positive day = GD 0). Caesarean sections were performed on GD 20 and fetuses were evaluated for viability, growth, and external, visceral, and skeletal abnormalities. Each group consisted of 25 females, with at least 21 per group being pregnant. The highest dose level caused decreases in maternal weight gain during some of the measurement intervals and was statistically significant during the GD 18-20 interval. Maternal food consumption was significantly decreased in the highest dose group over the dosing period (GD 6-20). There were no differences from control in any of the developmental parameters measured, including embryo/fetal viability, fetal weight, malformations, or variations. Based on the results of this study, the maternal NOAEL for butylparaben was 100 mg/kg/day. Butylparaben does not have the potential to cause developmental toxicity in the Sprague-Dawley rat at oral dosages up to 1000 mg/kg/day.     

Developmental Toxicity of the HMG‐CoA Reductase Inhibitor (PPD10558) in Rats and Rabbits

PPD10558 is an orally active, lipid‐lowering 3–hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase inhibitor (statin) being developed as a treatment for hypercholesterolemia in patients who have not been able to tolerate statins because of statin‐associated myalgia. We have studied the potential developmental toxicity effects of PPD10558 in pregnant rats and rabbits given daily oral doses during the period of organogenesis. Rats were dosed with 0, 20, 80, or 320 mg/kg/day from Gestation Day (GD) 6 to 17 and rabbits received dose levels of 0, 12.5, 25, or 50 mg/kg/day from GD 6 to 18. Additional groups in both studies served as toxicokinetic animals and received the PPD10558 in the same manner as the main study groups at the same dose levels. Blood samples were collected from toxicokinetic animals at designated time points on GD 6 and 17 in rats and GD 6 and 18 in rabbits. Fetal exposure in rats was assessed on GD 20. Maternal and developmental parameters were evaluated in rats and rabbits on GD 20 and GD 29, respectively. No maternal and developmental toxicity was observed at any of the dose levels used in the rat study. Evidence of fetal exposure was determined in fetal plasma with mean fetal concentrations of PPD10558 and the metabolite (PPD11901) found to be between 1 and 6% of the mean maternal concentrations. In rabbits, marked maternal toxicity including mortality (eight deaths; 1 dose at 25 and 7 at 50 mg/kg/day), abortions (2 at 25 mg/kg/day and 6 at 50 mg/kg/day) and reduction in gestation body weight, gestation body weight changes and decreased food consumption were observed. In addition, fetal body weights of the combined sexes were significantly reduced at 50 mg/kg/day in comparison with the controls. Mean peak exposure (Cmax) and total exposure (AUC(0–24)) of PPD11901 in both rats and rabbits were higher than that of PPD10558 on GD 6 and GD 17 at each of the three dose levels.. Based on the results of these studies, the no observed adverse effect level (NOAEL) for maternal and developmental toxicity in rats was considered to be ≥320 mg/kg/day, the highest dose level used in the study. The NOAEL for maternal and developmental toxicity in rabbits was 12.5 mg/kg/day and 25 mg/kg/day, respectively.     

Two generation reproduction study of ethylbenzene by inhalation in Crl-CD rats

BACKGROUND: This study was conducted to evaluate the potential adverse effects of ethylbenzene (EB) on reproductive capability from whole-body inhalation exposure of F0 and F1 parental animals. METHODS: Four groups of Crl:CD(SD)IGS BR rats (30/sex/group for F0 and 25/sex/group for F1) were exposed to 0, 25, 100, and 500 ppm EB for 6 hr/day for at least 70 consecutive days before mating. Inhalation exposure for the F0 and F1 females continued throughout mating, gestation through gestation day (GD) 20, and lactation days (LD) 5-21. On LD 1-4, females received EB in corn oil via oral gavage at dose levels of 26, 90, and 342 mg/kg/day (divided into three equal doses, approximately 2 hr apart), as calculated from a physiologically-based pharmacokinetic (PBPK) model to provide similar maternal blood area-under-concentration (AUC) as provided by inhalation. Pups were weaned on postnatal day (PND) 21 and exposure of the F1 generation started on PND 22. Estimates of internal exposure were determined by measuring EB concentrations in blood collected from F1 dams (4/group) and their culled pups 1 hr after the last gavage dose on PND 4. On PND 22, blood was collected from these same F1 dams and their weanlings for EB analysis 1 hr after a 6-hr inhalation exposure. The remainder of the F2 generation was not directly exposed. RESULTS: EB exposure did not affect survival or clinical observations. Male rats in the 500 ppm group in both generations gained weight more slowly than the controls. There were no indications of adverse effects on reproductive performance in either generation. Male and female mating and fertility indices, pre-coital intervals, spermatogenic endpoints, ovarian follicle counts, reproductive organ weights, lengths of estrous cycle and gestation, live litter size, pup weights, developmental landmarks, and postnatal survival were unaffected. No adverse exposure-related macroscopic pathology was noted at any level. CONCLUSIONS: Increased liver weights were found in the animals exposed to 500 ppm. F1 maternal whole blood EB concentrations of 0.49, 3.51, or 18.28 mg/L were found 1 hr after administration of a composite oral dose of 26, 90, or 342 mg/kg/day, respectively, but no detectable EB was found in blood samples of their F2 PND 4 culled pups. F1 maternal mean whole blood EB levels 1 hr after a 6-hr inhalation exposure on postpartum day (PPD) 22 was 0.11 mg/L (25 ppm), 0.56 mg/L (100 ppm), and 11 mg/L (500 ppm). For the offspring exposed with their dams on PND 22, F2 pup blood EB concentrations ranged from 0.017-0.039 mg/L (25 ppm), 0.165-0.465 mg/L (100 ppm), and 8.82-15.74 mg/L (500 ppm). Because decreased weight gain in the 500 ppm males was transient and no histopathological changes were associated with the increased liver weights in the 500 ppm male and female groups, these changes were not considered adverse. Therefore, for parental systemic toxicity, 100 ppm was considered a NOEL and 500 ppm a NOAEL in this study. The 500 ppm exposure concentration was considered a NOAEL for F0 and F1 reproductive toxicity and offspring developmental endpoints.     

Postnatal development of rat pups after maternal exposure to diethanolamine

BACKGROUND: Diethanolamine (DEA), a widely used surfactant, was administered to pregnant mice at the oral LD10 resulting in failure of pups to grow and thrive through postnatal day (PND) 3 [National Toxicology Program, 1987; York et al., Teratology 37:503-504, 1988]. The toxicity profile for DEA differs among rodent species. This study investigated DEA-induced postnatal toxicity in a second species. METHODS: Timed-mated Sprague-Dawley rats were dosed (0, 50, 125, 200, 250, or 300 mg DEA/kg/day, p.o.) on gestational days (GD) 6-19. Dams and pups were monitored for body weight, feed/water intake, clinical signs, litter size, and sex ratio. At necropsy (PND 21), maternal liver and kidney weights and number of uterine implantation sites were recorded. RESULTS: The high-dose group was terminated early due to excessive toxicity. The estimated maternal LD10 was 218 mg/kg/day. Maternal effects included decreased body weight and relative feed intake (>or=200 mg/kg/day), transiently reduced relative water intake (125 and 250 mg/kg/day), and increased absolute kidney weight (>or=125 mg/kg/day). Postimplantation loss (PND 0) and pup mortality (PND 0-4) were increased (>or=200 and >or=125 mg/kg/day, respectively). Pup body weight was reduced (>or=200 mg/kg/day) as late as PND 21. CONCLUSIONS: This study demonstrates reduced postnatal growth and survival in a second species after gestational exposure to DEA, persistence of toxic effects through the end of lactation, possibly due to long elimination half-life, and maternal and developmental toxicity no-observed-adverse-effect level (NOAELs) (50 mg/kg/day) and lowest-observed-adverse-effect level (LOAELs) (125 mg/kg/day) for oral DEA exposure during embryo/fetal development in the rat.     

Pre- and postnatal development studies of lasofoxifene, a selective estrogen receptor modulator (SERM), in Sprague-Dawley rats

BACKGROUND: Lasofoxifene is a nonsteroidal selective estrogen receptor modulator (SERM) developed for the treatment of postmenopausal osteoporosis. The purpose of these studies was to evaluate the effects of lasofoxifene on the postnatal development, behavior, and reproductive performance of offspring of female rats given lasofoxifene during organogenesis and lactation. METHODS: Two range-finding studies were conducted to determine the effects of lasofoxifene at doses from 0.01-10 mg/kg on parturition and lactation in pregnant rats and on the early postnatal development of the offspring, and to optimize the dosing regimen. Maternal milk and plasma were sampled for concentrations of lasofoxifene on Lactation Days 4, 7, and 14. In the pre- and postnatal development study, lasofoxifene was administered to pregnant and lactating rats by oral gavage at dose levels of 0.01, 0.03, and 0.1 mg/kg on Gestation Days 6-17 and Lactation Days 1-20. Maternal body weight and food consumption were measured throughout pregnancy, and body weight was measured throughout lactation. Parturition was monitored closely. The F1 offspring were measured for viability, body weight, anogenital distance, the appearance of postnatal developmental indices and reflex behaviors, sensory function, in an age-appropriate functional observational battery, motor activity, auditory startle, passive avoidance, and the Cincinnati Water Maze. The F1 generation was assessed for reproductive function, and the F2 offspring were measured for body weight and viability throughout the lactation period. RESULTS: In the range-finding studies, indications of maternal toxicity included decreased body weight and food consumption, increased length of gestation, prolonged parturition, dystocia, and increased offspring mortality at birth. Concentrations of lasofoxifene in maternal plasma were similar to those in milk, increased with increasing dose, and remained consistent over a 10-day period. In the pre- and postnatal development study, maternal body weights and food consumption were decreased in all treated groups during gestation. Length of gestation was increased, parturition was prolonged, and dystocia was noted in the dams in the 0.1 mg/kg group. There was increased pup mortality in the F1 litters in the 0.1 mg/kg group and all treated groups had decreased offspring body weights beginning at 1 week of age, continuing into the postweaning period and, for the F1 males, into adulthood. Female F1 offspring in the 0.03 and 0.1 mg/kg groups had increased body weights as adults. There were delays in the age of appearance of preputial separation in the males in the 0.1 mg/kg group and vaginal opening in the females in all treated groups. Body temperature was decreased by <0.5 degrees C after weaning for male and female offspring in the 0.1 mg/kg group. The sensory, behavioral, and functional measures, including the tests of learning and memory, were unaffected by treatment. Mating success was lower for the F1 animals in the 0.1 mg/kg group, but there were no effects on the reproductive parameters. Mating, reproduction, and maternal behavior of the F1 animals in the 0.01 and 0.03 mg/kg groups and the survival and body weights of the F2 offspring in all treated groups through Postnatal Day 21 were unaffected by treatment. CONCLUSION: The maternal findings in this study were related to the pharmacologic activity of lasofoxifene. Inhibition of growth of the F1 offspring after perinatal exposure to lasofoxifene was observed, but there were no significant effects on the sensory, behavioral, or functional measures, including learning and memory. There were no effects on the F2 generation. The findings are consistent with those reported for at least one other SERM. The findings of this study do not suggest increased risk for the primary indication of use in postmenopausal women.     

Embryotoxicity of oral administered chlorothalonil in mice

BACKGROUND: Chlorothalonil (2,4,5,6-tetrachloroisophthalonitril), the nephrotoxic fungicide, was examined for its potential to produce developmental toxicity in mice after oral administration. METHODS: Pregnant ICR (CD-1) mice were given sublethal doses of 0 (corn oil), 100, 400, and 600 mg/kg/day chlorothalonil by gavage on gestation days (GD) 6-15. RESULTS: Maternal effects in 400 and 600 mg/kg/day dose groups included signs of toxicity such as weakness and depression in the maternal activity, and reduction in body weight and weight gain. No maternal toxicity was apparent in the 100 mg/kg/day dose group. Maternal exposure to chlorothalonil during organogenesis significantly affected the number of live fetuses, early resorption, and mean fetal weight in the 400 and 600 mg/kg/day dose groups. No external, visceral, and skeletal abnormalities were observed among any of the treated groups compared to the control. CONCLUSIONS: On the basis of the present results chlorothalonil can produce clinical signs of toxicity and fetotoxicity without teratogenic effects at 400 and 600 mg/kg/day dose groups.     

Postnatal closure of membranous ventricular septal defects in Sprague-Dawley rat pups after maternal exposure with trimethadione

BACKGROUND: Congenital membranous ventricular septal defects (VSD) have been shown to close during postnatal development in rats [Solomon et al., Teratology 55:185-194, 1997]. Although they may differ in size, spontaneous and treatment-related VSD are histologically similar; however, the postnatal fate of treatment-induced VSD is not known. The objective of this study was to determine if treatment-induced VSD persist throughout postnatal development. METHODS: Groups of 40 female rats were given oral doses of trimethadione (TMD) at 400 mg/kg/day (200 b.i.d.) or 600 mg/kg/day (300 b.i.d.) on Gestation Days (GD) 9 and 10. Twenty dams in each group were designated for Cesarean section and 20 were allowed to deliver and rear their offspring to Postnatal Day (PND) 21. The integrity of the ventricular septum was evaluated in fetuses (GD 21) and pups (PND 21). RESULTS: The incidence of membranous VSD was 0.6, 7.6, and 49.8% per litter in the Control, 400, and 600 mg/kg groups, respectively, on GD 21. Both the incidence and severity of VSD increased with dose. The VSD at 400 mg/kg were small in size and initially detected by the presence of blood flowing through the defect from the closed right ventricle. In the 600 mg/kg dose group, the VSD, although still membranous, were larger and more readily detected without the need to examine the blood flow. At 600 mg/kg, not only were the VSD larger than those in the Control or the 400 mg/kg group, 10.1% per litter of the affected fetuses had other vessel anomalies associated with the VSD, which were incompatible with pup survival. On PND 21, VSD was noted in 0.3, 0, and 6.4% per litter evaluated in the Control, 400, and 600 mg/kg groups, respectively. This demonstrates that the small, isolated treatment-related VSD can resolve postnatally; however, the closure of the larger or more severe VSD may be prolonged or may not occur at all. Although TMD exposure reduced group mean fetal weights at both dose levels, there was no difference between the mean weight of fetuses with VSD and those fetuses without VSD in the same group. CONCLUSION: Treatment-induced VSD close postnatally, and appears to be a delay in cardiac development not associated with fetal weight. The timing of closure and survivability during closure is dependent on the severity of the VSD. Further characterization of the two sizes of VSD may provide diagnostic clarity; however, the current data support the smaller VSD as a variation with no significant impact on viability and growth, and the more severe VSD to be a malformation.     

Effects of gestational exposure to ethane dimethanesulfonate in CD-1 mice: microtia and preliminary hearing tests

BACKGROUND: Microtia is a reduction in pinna size, usually seen in humans in conjunction with other medical conditions. We report microtia in CD‐1 mice after gestational exposure to ethane dimethanesulfonate (EDS), an alkylating agent and adult rat Leydig cell toxicant. METHODS: Time‐pregnant CD‐1 mice were administered 0, 80, or 160 mg EDS/kg on gestation days (GD) 11–17, or 0 or 160 mg EDS/kg on GD 11–13, GD 13–15 or GD 15–17. Pinnae were measured on postnatal days (PND) 4, 8, 18, and 28; and were observed for detachment from birth through PND 8. Branchial‐arch derived skeletal structures and histology of the pinna was examined on PND 4 and 24. Brainstem auditory evoked response (BAER) tests were carried out at approximately PND 160 to determine possible effects on hearing. RESULTS: All offspring of EDS‐treated dams exhibited bilateral, dose‐related decreases in pinna size. Gestational exposure during GD 11–13 produced smaller ears than during GD 13–15 or 15–17, but not as small as the GD 11–17 regimen. Ossification of other pharyngeal arch derivatives was delayed whereas histology was unremarkable. BAER analysis showed a decrease in the proportion of adult offspring producing a quantifiable response to varied auditory stimuli among EDS‐treated litters. CONCLUSIONS: Gestational exposure to EDS affects pinna development in the mouse, with a broad period of sensitivity during the second half of gestation. Microtia induced by EDS may be associated with hearing deficits, suggesting functional importance of pinna size or additional effects of EDS on ear development not detected by morphological examination. Birth Defects Res B68:383–390, 2003. © 2003 Wiley‐Liss, Inc.     

Developmental toxicity of temafloxacin hydrochloride in the long-tailed macaque (Macaca fascicularis)

The potential developmental toxicity of temafloxacin hydrochloride was studied in the long-tailed macaque (Macaca fascicularis). Ten animals in each of the three drug-treated groups (25, 50, and 100 mg/kg) were administered temafloxacin via nasogastric intubation during gestational days (GD) 20-50. A control group of ten animals received vehicle only. The dams were monitored daily for adverse physical signs and maternal blood samples were collected for analyses of serum progesterone (P), 17 beta-estradiol (E2), and chorionic gonadotropin (CG). In addition, the conceptus was monitored periodically by ultrasound during gestation to confirm growth and viability. Increased maternal toxicity (weight loss, anorexia, emesis) and embryolethality were observed at 100 mg/kg, and a no-observable-adverse-effect-level (NOAEL) of 50 mg/kg was established. The incidence of prenatal mortality was as follows: Control = 1/10 (10%); 25 mg/kg = 1/10 (10%); 50 mg/kg = 2/10 (20%); and 100 mg/kg = 5/10 (50%). Analysis of P, E2, and CG indicated no significant effect of treatment. In addition, no significant differences were observed in embryonic/fetal growth and development when compared to historical controls. No gross structural changes were observed in fetuses exposed to 50 or 100 mg/kg, although one fetus exposed to 25 mg/kg exhibited microphthalmia. This anomaly was considered spontaneous and, therefore, unrelated to treatment.     

Ameltolide. I: Developmental toxicology studies of a novel anticonvulsant

Ameltolide, a novel anticonvulsant agent, has been shown in animal models to be effective in controlling seizures. The developmental toxicity of ameltolide was evaluated in two species. Naturally mated rats and rabbits were dosed once daily by gavage on gestation days (GD) 6-17 and 6-18, respectively. Rats were given doses of 0, 10, 25, or 50 mg/kg; rabbits were given 0, 25, 50, or 100 mg/kg. Laparotomy was performed on rats on GD 20 and on rabbits on GD 28. In rats, maternal toxicity was indicated at the 25- and 50-mg/kg dose levels by depressed body weight gain. Fetal body weight was depressed at the 50-mg/kg dose level. Fetal viability and morphology were not affected. The no-observed effect levels (NOEL) for adult and developmental toxicity in the rat were 10 and 25 mg/kg, respectively. In rabbits, maternal toxicity was indicated by a net loss in body weight at the 50- and 100-mg/kg dose levels. Fetal viability and body weight were depressed at the 100 mg/kg dose level. Shortened digits occurred on the right forepaw of one fetus at the 50-mg/kg dose level (in conjunction with severe maternal toxicity) and on the hindpaws of two fetuses from separate litters at the 100-mg/kg dose level. Incomplete ossification of the phalanges occurred on the forepaws of nine fetuses from four litters at the 100-mg/kg dose level. Ameltolide was weakly teratogenic in the rabbit. The NOEL for adult and developmental toxicity in the rabbit was 25 mg/kg.     

Developmental toxicity and uterotrophic studies with di-2-ethylhexyl terephthalate

BACKGROUND: These studies were conducted to evaluate the potential adverse effects of di-2-ethylhexyl terephthalate (DEHT) exposure on in utero development in mice and rats. In addition, a uterotrophic assay for estrogenic activity was conducted in sexually immature rats. METHODS: In the developmental toxicity studies, diet containing DEHT was fed to four groups of mated female Crl:CD(SD)IGS BR rats (25/group) from gestation day (GD) 0-20 or Crl:CD1(ICR) mice (25/group) from GD 0-18. Concentrations within the feed were 0, 0.3, 0.6, and 1.0% for the rats and 0, 0.1, 0.3, and 0.7% for the mice. Laparohysterectomies were carried out on the last day of exposure and the numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. The fetuses were weighed, sexed, and examined for external, visceral and skeletal malformations, and developmental variations. The dose rate from dietary DEHT exposure was 0, 226, 458, and 747 mg/kg/day in the rats and 197, 592, and 1382 mg/kg/day in the mice for the control, low, mid, and high-exposure groups, respectively. RESULTS: DEHT exposure did not affect clinical observations. A slight reduction in body weight gain was noted in the high-dose level rat group; the remaining groups were unaffected. At necropsy, increased liver weights were noted in the high-dose rat group and the mid- and high-dose mouse groups. Mean numbers of implantation sites and viable fetuses, mean fetal weights, and mean litter proportions of preimplantation loss, early resorptions, late resorptions, and fetal sex ratios were unaffected by DEHT exposures. No test article-related malformations or variations were observed at any concentration level in the rat and mouse developmental toxicity studies. In the uterotrophic assay for estrogenic activity, sexually immature female rats received oral gavage doses 20, 200, or 2000 mg DEHT/kg bw/day from postnatal day (PND) 19-21. A slight reduction in rate of body weight gain was noted on the first day of dosing in the high dose group, but no other indications of toxicity were evident. DEHT exposure did not affect wet or blotted uterine weight parameters in any of these dose groups. The NOEL for developmental toxicity in rats was 747 mg/kg/day and 1382 mg/kg/day in mice. The NOEL for estrogenic activity was 2000 mg/kg/day. The NOEL for maternal toxicity was 458 mg/kg/day in rats and 197 mg/kg/day in mice. CONCLUSIONS: The lack of adverse developmental effects with DEHT exposure are in contrast to the adverse developmental effects noted after di-2-ethylhexyl phthalate (DEHP) exposure. The difference between the effects noted with the ortho-constituent (DEHP) and the lack of effects reported with the para-constituent (DEHT) is due most likely to differences in metabolism and the formation of the stable monoester, mono-2-ethylhexyl phthalate (MEHP) from the DEHP moiety.     

Critical window of male reproductive tract development in rats following gestational exposure to di-n-butyl phthalate

BACKGROUND: Gestational exposure to di-n-butyl phthalate (DBP), a ubiquitous environmental contaminant, has been shown to interfere with the development of the male reproductive tract by acting as an antiandrogen. This study was conducted to identify the critical days for the abnormal development of the male reproductive tract, specifically the testis and epididymis. METHODS: Timed-pregnant Sprague-Dawley rats were dosed with DBP at 500 mg/kg/day on gestation day (GD) 14 and 15, 15 and 16, 16 and 17, 17 and 18, 18 and 19, or 19 and 20 (GD 0=plug day). Anogenital distance (AGD) was measured on postnatal day (PND) 1 and 13, while areloa number was recorded on PND 13 only. After weaning, males were allowed to mature to PND 90 at which time they were necropsied. Areloa number and AGD were recorded and testes, epididymides, seminal vesicles, prostate gland, kidneys, and liver weighed. Blood serum was collected and assayed for total testosterone concentration. RESULTS: There were no observable effects on litter size, sex ratio, serum testosterone concentration, or mortality of pups. Statistically significant permanent reductions in AGD were seen in males exposed prenatally to DBP on GD 15 and 16 or GD 18 and 19. On PND 13, areola were present in males exposed to DBP on GD 15 and 16, 16 and 17, 17 and 18, and 19 and 20. However, permanent retention occurred only in males after DBP exposure on GD 16 and 17. Exposure to DBP on only GD 17 and 18 elicited a reduction in epididymal weights; while exposure on only GD 16 and 17 caused a significant increase in the weights of the testes due to edema. In this study, epididymal and testicular malformations were most prevalent after exposure to DBP on any gestational day. Epididymal malformations, characterized by agenesis of various regions and small or flaccid testes were significantly increased in DBP-exposed males only on GD 16 and 17. CONCLUSIONS: These findings suggest that 2-day DBP exposure is highly detrimental to the developing reproductive tract of the male fetus and the critical window for abnormal development is GD 16-18.     

The role of maternal toxicity in lovastatin-induced developmental toxicity

The role of maternal toxicity in lovastatin-induced developmental toxicity in rats was examined in a series of studies. The first study administered lovastatin at 100, 200, 400, or 800 mg/kg/day (mkd) orally to mated rats from Gestation Day (GD) 6 through 20. Maternal toxicity was observed as transient dose-related body weight losses at the initiation of dosing; there were also deaths and/or morbidity at 400 and 800 mkd. These toxicities occurred in conjunction with forestomach lesions. Mean fetal weights were decreased in all groups (-5 to -16%), and the incidence of skeletal malformations, variations, and incomplete ossifications was increased. The 2 highest doses produced the most severe maternal and developmental effects. Using the same dosages, the second study avoided gestational maternal weight losses and morbidity by starting treatment 14 days before mating with dosing continued to GD 20. There were transient dose-related body weight losses after the start of dosing and deaths in the 400- and 800-mkd groups; however, there was no evidence of maternal toxicity during gestation. Developmental toxicity was evident only as slight, but generally significant (p< or =0.05) decreases in mean fetal weights in groups given > or =200 mkd (-2 to -5%). Significantly, no skeletal abnormalities were observed. A third study administered the pharmacologically active metabolite of lovastatin subcutaneously at dose levels that matched oral maternal drug exposures. In the high-dose group, maternal weight gain and mean fetal weight were slightly decreased but there were no treatment-related skeletal abnormalities. Finally, a series of toxicokinetic studies assessed whether the 2 different developmental toxicity profiles were due to differences in drug exposure between the developmentally toxic and non-toxic dosing regimes. The data showed that groups with no skeletal abnormalities had maternal and embryonic/fetal drug concentrations similar to or even greater than the groups with fetal abnormalities. These results indicate that fetal skeletal abnormalities observed at lovastatin dose levels > or =100 mkd are not due to a direct teratogenic effect, but are the result of excessive maternal toxicity, which most likely involves a nutritional deficiency associated with forestomach lesions and reduced maternal food intake.     

Developmental toxicity of orally administered technical dimethoate in rats

BACKGROUND: Dimethoate (O,O-dimethyl-S-(N-methylcarbamoyl-methyl) phosphorodithioate), an organophosphate insecticide, was examined for its potential to produce developmental toxicity in rats after oral administration. METHODS: Pregnant Fischer 344 rats were given sublethal doses of 0 (corn oil), 7, 15, and 28 mg/kg/day dimethoate by gavage on gestation days (GD) 6-15. Maternal effects in 15 and 28 mg/kg/day dose groups included cholinergic signs such as tremors, diarrhea, weakness, and salivation, and depression in the maternal and fetal brain acetylcholinesterase (AChE) activities. Other maternal toxicity that included reduction in body weight and feed consumption was observed only in the treated group of 28 mg/kg/day. No maternal toxicity was apparent in the 7 mg/kg/day dose group. RESULTS: Maternal exposure to dimethoate during organogenesis significantly affected the number of live fetuses, early resorption, and mean fetal weight in the 28 mg/kg/day dose group. No external, visceral, and skeletal abnormalities were observed in any of the treated groups compared to the control. CONCLUSIONS: On the basis of the present results dimethoate can produce clinical signs of toxicity and significant inhibition of the maternal and fetal AChE activities in dose groups of 15 and 28 mg/kg/day and showed fetotoxicity without teratogenic effects at 28 mg/kg/day.     

Embryo/fetal toxicity assessment of lasofoxifene, a selective estrogen receptor modulator (SERM), in rats and rabbits

BACKGROUND: The purpose of this study was to evaluate the effects of lasofoxifene, a selective estrogen receptor modulator (SERM), on rat and rabbit fetal development. METHODS: Lasofoxifene was administered orally to rats (1, 10, 100 mg/kg) between gestation days (GD) 6-17, and in rabbits (0.1, 1, 3 mg/kg) between GD 6-18. Maternal body weight and food consumption were monitored throughout pregnancy. Fetuses were delivered by Cesarean section on GD 21 in rats, and GD 28 in rabbits, to evaluate fetal viability, weight, and morphology. Drug concentrations in maternal plasma were measured in a separate cohort of animals at several time points commencing on GD 17 (rats) and 18 (rabbits). On GD 18 (rat) and GD 19 (rabbit) drug concentrations were measured in maternal plasma and in fetal tissue 2 hr post dosing to determine the fetal to maternal drug ratio. RESULTS: In rats, there were dose-related declines in maternal weight gain and food consumption. Post implantation loss was significantly increased at dosages of 10 and 100 mg/kg, and the number of viable fetuses was decreased at 100 mg/kg. The placental weights increased, whereas fetal weights decreased in a dose-dependent manner. Lasofoxifene-related teratologic findings were noted at 10 and 100 mg/kg and included imperforate anus with hypoplastic tails, dilatation of the ureters and renal pelvis, misaligned sternebrae, hypoflexion of hindpaw, wavy ribs, and absent ossification of sternebrae. In rabbits, neither maternal weight gain nor food consumption were affected during treatment. Between GD 26-28, there was a dose-dependent increased incidence of red discharge beneath the cages. At 1 and 3 mg/kg, resorptions and post-implantation loss increased. There were no significant external or visceral effects, but 3 mg/kg there was an increased incidence of supernumerary ribs. Although the maternal plasma Cmax and AUC(0-24) were dose-dependent, the exposures in the rat were many orders of magnitude greater than in the rabbit even for the same 1 mg/kg dose. The single time point fetal/maternal drug ratio was higher in the rat (1.3-0.78) than in the rabbit (0.21-0.16). CONCLUSION: In general, both maternal and fetal effects of lasofoxifene were similar to those reported with other SERMs. Although the incidence or severity of these effects was, in some instances, greater in the rat than in the rabbit, the doses and the resultant maternal and fetal exposures were many orders of magnitude higher in the rat, suggesting the rabbit to be more sensitive to the toxicological effects of lasofoxifene.     

Developmental toxicity evaluation of emodin in rats and mice

BACKGROUND: Emodin, a widely available herbal remedy, was evaluated for potential effects on pregnancy outcome. METHODS: Emodin was administered in feed to timed-mated Sprague-Dawley (CD) rats (0, 425, 850, and 1700 ppm; gestational day [GD] 6-20), and Swiss Albino (CD-1) mice (0, 600, 2500 or 6000 ppm; GD 6-17). Ingested dose was 0, 31, 57, and approximately 80-144 mg emodin/kg/day (rats) and 0, 94, 391, and 1005 mg emodin/kg/day (mice). Timed-mated animals (23-25/group) were monitored for body weight, feed/water consumption, and clinical signs. At termination (rats: GD 20; mice: GD 17), confirmed pregnant dams (21-25/group) were evaluated for clinical signs: body, liver, kidney, and gravid uterine weights, uterine contents, and number of corpora lutea. Fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations/variations. RESULTS: There were no maternal deaths. In rats, maternal body weight, weight gain during treatment, and corrected weight gain exhibited a decreasing trend. Maternal body weight gain during treatment was significantly reduced at the high dose. In mice, maternal body weight and weight gain was decreased at the high dose. CONCLUSIONS: Prenatal mortality, live litter size, fetal sex ratio, and morphological development were unaffected in both rats and mice. At the high dose, rat average fetal body weight per litter was unaffected, but was significantly reduced in mice. The rat maternal lowest observed adverse effect level (LOAEL) was 1700 ppm; the no observed adverse effect level (NOAEL) was 850 ppm. The rat developmental toxicity NOAEL was > or =1700 ppm. A LOAEL was not established. In mice, the maternal toxicity LOAEL was 6000 ppm and the NOAEL was 2500 ppm. The developmental toxicity LOAEL was 6000 ppm (reduced fetal body weight) and the NOAEL was 2500 ppm.     

Effects of age and weaning on the immature rat uterotrophic assay using ethynylestradiol.

The purpose of this study was to evaluate the most appropriate rat age for the start of administration, and the effect of weaning, in the immature rat uterotrophic assay using ethynylestradiol (EE). Animals weaned on postnatal day (PND) 20 were administered subcutaneously EE at doses of 0.06-6 micrograms/kg/day for 3 days beginning on PND 21, 23 or 25. EE at the same doses was also administered to rats weaned on PND 17 or 20 from PND 21 for 3 days. Although uterine weight was significantly increased in the rats given 0.6-6 micrograms/kg EE in both of the studies, the percentage increase relative to the control in each group given EE from PND 21 and weaned on PND 20 was higher than in those groups given EE from PND 23 or 25, and the group weaned on PND 17.     

Teratogenicity of all-trans retinoic acid during early embryonic development in the cynomolgus monkey (Macaca fascicularis).

The embryotoxic and teratogenic potential of all-trans retinoic acid was assessed following exposure prior to and during early organogenesis in the cynomolgus monkey (Macaca fascicularis). Sixteen pregnant females were orally administered all-trans retinoic acid (Tretinoin, Hoffmann-La Roche) once daily from GD 10-20 and twice daily from GD 21-24 at three different dosages, 5 (n = 9), 10 (n = 6) and 20 mg/kg (n = 1). Adverse clinical signs resembling hypervitaminosis A were observed in one animal at 5 mg/kg, in three animals at 10 mg/kg, and in the animal treated with 20 mg/kg all-trans retinoic acid. Maternal weight loss was observed in the 10- and 20-mg/kg groups. A dose-dependent increase in embryolethality was observed, with 22% (2/9), 50% (3/6), and 100% (1/1) occurring at 5, 10, and 20 mg/kg, respectively. The majority of embryonic deaths occurred between GD 16 and 20; the incidence of these early losses was higher than in historical and concurrent controls. No malformations, but a single growth-retarded fetus, was observed in the 5-mg/kg group. Craniofacial malformations, consisting of external ear defects, mandibular hypoplasia, cleft palate, and temporal bone abnormalities, were seen in three viable fetuses in the 10-mg/kg group. Skeletal variations were common to the majority (70%, 7/10) of viable fetuses in both dose groups and were increased relative to historical controls (32%, 25/77). Unlike previous studies with 13-cis-retinoic acid during the pre- and early organogenic stages of development (Hummler et al., Teratology 42:263-272, 1990), no thymic hypo- or aplasia or heart anomalies were observed, which may be attributable to the slightly longer 13-cis retinoic acid treatment period, i.e., GD 10-27. However, external ear and temporal bone defects were common to both all-trans and 13-cis retinoic acid. The similarity observed in the malformation syndrome induced by both all-trans and 13-cis retinoic acid in the cynomolgus monkey and 13-cis retinoic acid embryopathy in humans supports this macaque species as a model for further developmental toxicity studies of vitamin A-related compounds.     

Reversible effects of triamcinolone and lack of effects with aspirin or L-656,224 on external genitalia of male Sprague-Dawley rats exposed in utero.

Inhibitors of the arachidonic acid cascade were given to pregnant rats during the critical period for morphogenesis of the external genitalia. Groups treated subcutaneously (s.c.) with 0.1 or 0.25 mg/kg/day of triamcinolone acetonide (TA) on gestational days (GD) 14-19 had male fetuses on GD 20 with moderate decreases in absolute anogenital distance (AGD), but gross and histological examinations revealed no alterations to the genital tubercle (i.e., no hypospadias). The s.c. coadministration of arachidonic acid at 100 mg/kg/day had minimal to no effect on AGD in the TA-exposed groups. No effect on AGD was observed in male fetuses from groups administered aspirin orally at 150 mg/kg/day, and only a 6% decrease was observed in the 300-mg/kg/day group. Neither TA nor aspirin adversely affected AGD of female fetuses. In another study, TA was administered on GD 11-19 at dose levels of 0.05 and 0.1 mg/kg/day, and dams were allowed to deliver. High-dose male offspring examined on postcoitum day (PCD) 23, had moderate decreases in AGD. In both studies with TA, there were also significant decreases in offspring weights. The contribution of the decreased weight to the decrease in absolute AGD was examined by a variety of methods (ratio of AGD to cube root of weight or biparietal distance, comparison to weight-matched controls, and covariance analysis). We conclude that TA caused a specific decrease in AGD on GD 20 that was largely reversed by PCD 23. When examined as adults (8 weeks old), the external genitalia of TA-exposed offspring were normal. Thus, the TA-induced decreases in AGD on GD 20 did not predict irreversible malformation. TA also caused other effects, which included a somewhat flattened genital tubercle and apparently thinned and glossy skin between the tubercle and the anus in both sexes on GD 20 and PCD 23, but not as adults. In addition, there were high pup mortality and high incidences of micrognathia and omphalocele (in the 0.25-mg/kg/day group only). Aspirin at 75 or 150 mg/kg/day and a specific lipoxygenase inhibitor (L-656,224) at 1,000 or 2,000 mg/kg/day were also administered from GD 14 to 19, and no offspring effects were observed. Thus, of the three agents that potentially inhibit the arachidonic acid cascade, only triamcinolone produced moderate effects on rat external genitalia that were largely reversible.(ABSTRACT TRUNCATED AT 400 WORDS)