Search

Prenatal exposure to 100 mg/kg atrazine (ATR) delays mammary gland (MG) development in resulting female offspring of Long-Evans rats. To determine if the fetal MG was sensitive to ATR effects during specific periods of development, timed-pregnant dams (n = 8/group/block) were dosed for 3- or 7-gestation day (GD) intervals (GD 13-15, 15-17, 17-19, or 13-19) with 100 mg ATR/kg/day or vehicle (C), and their offspring were evaluated for changes. Mammary glands taken from pups prenatally exposed to ATR displayed significant delays in epithelial development as early as postnatal day (PND) 4 compared to C, with continued developmental delays at later time points that varied by time of exposure. However, the most persistent and severe delays were seen in the GD 17-19 and GD 13-19 ATR exposure groups, demonstrating statistically similar growth retardation. Because MG developmental deficits persisted into adulthood, we hypothesized that ATR-exposed animals may have had difficulties nursing their young. Females exposed prenatally to either ATR (as defined) or C (n = 4 litters/group) were bred, and the resulting F 2 offspring from GD 17-19 and GD 13-19 exposure groups were significantly smaller in body weight (BW) than C. In a separate study, it was determined that ATR (25-100 mg/kg), delivered from GD 15-19, did not decrease fetal body weights on GD 20, even though the higher doses significantly decreased weight gain of the dosed dams. These data suggest that the consequences of brief ATR exposure during a critical period of fetal MG development (GD 17-19), are both delayed MG development of the offspring and inadequate nutritional support of F 2 offspring, resulting in adverse effects on pup weight gain.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure produces hydronephrosis and cleft palate in mice. These responses are corre- lated with disruption of expression of epidermal growth factor (EGF) receptor ligands, primarily EGF and transforming growth factor- alpha (TGF-a), and altered epithelial cell proliferation and differen- tiation. This research examined the role of these growth factors in TCDD-induced teratogenicity by using wild type (WT) and knockout (-/-) mice that do not express EGF, TGF-a, or both EGF and TGF-a. Pregnant females were weighed on GD 12 and dosed by gavage with either corn oil or TCDD at 24 mg/kg, 5 ml/kg. On GD 17.5, the maternal parameters evaluated included body weight, body weight gain, liver weight (absolute and adjusted for body weight). The number of implantations, live and dead fetuses, early or late resorp- tions, the proportion of males, fetal body weight, fetal absolute and relative liver weight, placenta weight, incidence of cleft palate, and the severity and incidence of hydronephrosis were recorded. TCDD did not affect maternal weight gain, fetal weight, or survival, but maternal and fetal liver weights and liver-to-body weight ratios were increased in all genotypes. The WT and TGF-a (-/-), but not the EGF (-/-) and EGF 1 TGF-a (-/-) fetuses, developed cleft palate after exposure to 24 mg TCDD/kg. Hydronephrosis was induced by TCDD in all genotypes, with the incidence in EGF 1 TGF-a (-/-) fetuses comparable to that of the WT. The incidence and severity of this defect was substantially increased in EGF (-/-) and TGF-a (-/-). In conclusion, this study demonstrated that expression of EGF influ- ences the induction of cleft palate by TCDD. Also, EGF and TGF-a The environmental contaminant 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD, dioxin) is the most potent and extensively studied member of the polychlorinated aromatic hydrocarbon (PAH) family of compounds. Members of this family of com- pounds produce similar patterns of toxicity and appear to have a common mechanism of action (Birnbaum et al., 1985; Mc- Connell and Moore, 1979; Poland and Knutson, 1982). TCDD is produced during industrial and combustion processes such as chemical pulp bleaching and waste incineration (Abbott et al., 1987; Firestone et al., 1972). The widespread distribution and stability of TCDD have resulted in bioaccumulation of the compound throughout the environment and food chain (Mc- Connell and Moore, 1979). TCDD has been shown to induce a variety of toxic responses in laboratory animals such as carci- nogenicity, hepatotoxicity, fetotoxicity, reproductive toxicity, and teratogenicity (McConnell et al., 1978; Poland and Knut- son, 1982; Schwetz et al., 1973). Human exposure to TCDD currently occurs primarily via dietary consumption, although there have been several accidental and occupational exposures (Fingerhut et al., 1991; Mastroiacovo et al., 1988; Reggiani, 1989). Because of its relative resistance to metabolism, TCDD tends to persist in the body and its half life in humans is estimated at 7 to 10 years (Pirkle et al., 1989). TCDD is a reproductive and developmental toxicant in wild- life and laboratory animals, including rats, hamsters, and mice. The primary teratogenic abnormalities produced in mice are hydronephrosis and cleft palate (Moore, 1973). In the C57BL/6N mouse, these responses are seen at doses that do not result in maternal or fetal mortality (Birnbaum et al., 1985).

Timed-pregnant CD(R) outbred albino Sprague-Dawley rats received formamide (50, 100, or 200 mg/kg/day) or vehicle (5 ml/kg deionized/distilled water, po) on gestational days (gd) 6 through 19. Maternal food and water consumption (absolute and relative), body weight, and clinical signs were monitored at regular intervals throughout gestation. At termination (gd 20), confirmed-pregnant females (21-23 per group) were evaluated for clinical status and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations and variations. There were no maternal deaths and no dose-related clinical signs. At 200 mg/kg/day, maternal body weight on gd 20, weight gain, and gravid uterine weight were significantly decreased. Maternal weight gain, corrected for gravid uterine weight, liver weight (absolute or relative), and food and water consumption (absolute or relative), were not affected. Formamide did not affect prenatal viability or incidences of fetal malformations or variations. Average fetal body weight/litter was decreased at 100 and 200 mg/kg/day. Fetal body weight was affected at lower daily doses than in previously published studies, possibly due to the longer total exposure period and/or lack of a recovery period between cessation of exposure and termination. In summary, the maternal toxicity no-observed-adverse-effect level (NOAEL) was 100 mg/kg/day and the low observed adverse effect level (LOAEL) was 200 mg/kg/day under the conditions of this study. Similarly, the developmental toxicity NOAEL was 50 mg/kg/day and the LOAEL was 100 mg/kg/day.

Mated Wistar rats, 25/group, were exposed to polymeric methylenediphenyl diisocyanate (MDI) aerosol of respirable size for 6 h/day, on gestational days (gd) 6 through 15, at 0, 1, 4, and 12 mg/m3. Maternal clinical signs, body weights, and feed and water consumption were measured throughout gestation. At scheduled sacrifice on gd 20, maternal body, gravid uterine, liver, and paired lung weights were documented. Corpora lutea were counted, implantation sites were identified: resorptions, dead and live fetuses, and placentas were weighed. All live fetuses were counted, sexed, weighed, and examined for external alterations; approximately 50% of the live fetuses/litter were preserved in Bouin's fixative and examined for visceral alterations, and the remaining live fetuses/ litter were cleared and stained with alizarin red S and examined for ossified skeletal alterations. Maternal toxicity was observed at 12 mg/m3, including mortality (2 of 24 pregnant), damage to the respiratory tract, reduced body weights and weight gain, reduced liver and increased lung weights, and reduced gravid uterine weight (the last not statistically significantly different from the control value). Developmental toxicity was also observed at 12 mg/m3, including reduced placental and fetal body weights and an increased incidence of fetal skeletal variations and skeletal retardations. There was no evidence of maternal or developmental toxicity at 1 or 4 mg/m3. The no observed adverse effect concentration for maternal and developmental toxicity was therefore 4 mg/m3. There were no treatment-related teratogenic effects at any concentrations evaluated.

Timed-pregnant CD-1 outbred albino Swiss mice received either methacrylamide (MAC; 0, 60, 120, or 180 mg/kg/day) or N,N'-methylenebisacrylamide (BAC; 0, 3, 10, or 30 mg/kg/day) p.o. in distilled water on gestational days (GD) 6 through 17. Maternal clinical status was monitored daily. At termination (GD 17), confirmed-pregnant females (27-30 per group, MAC; 24-25 per group, BAC) were evaluated for clinical status and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations. For MAC, no treatment-related maternal mortality was observed. Maternal body weight on GD 17, maternal weight gain during treatment and gestation, and corrected maternal weight gain were reduced at the high dose. Relative maternal food and water intake was not adversely affected; neurotoxicity was not observed. Relative maternal liver weight was increased at > or = 120 mg/kg/day; gravid uterine weight was decreased at 180 mg/kg/day. The maternal no-observed adverse effect level (NOAEL) was 60 mg/kg/day. The NOAEL for developmental toxicity was also 60 mg/kg/day. At > or = 120 mg/kg/day, mean fetal body weight was reduced. At 180 mg/kg/day, increased postimplantation death per litter was observed. Morphological development was not affected. The maternal NOAEL for BAC was 10 mg/kg/day. At 30 mg/kg/day, decreased maternal body weight on GD 17, maternal body weight change during treatment and gestation, corrected maternal body weight, and gravid uterine weight were observed. Relative maternal liver weight increased at 30 mg/kg/day. The developmental NOAEL was 3 mg/kg/day BAC. Mean fetal body weight was reduced at 30 mg/kg/day. At > or = 10 mg/kg/day, an increased incidence of fetal variations (extra rib) was observed, although fetal malformation rate was unaffected. MAC and BAC were not teratogenic to Swiss mice at the doses tested. BAC was more potent than MAC in causing adverse maternal and developmental effects.

This study evaluates the developmental toxicity and placental and milk transfer of N,N-dimethylformamide (DMF) in rats. Sprague-Dawley rats were given 0, 50, 100, 200, and 300 mg DMF/kg/day, by gavage, on Gestational Days (GD) 6 through 20. Maternal toxicity was indicated by depressions in weight gain and food consumption at doses >/=100 mg/kg. Fetal toxicity was indicated by decreased fetal body weight at doses >/=100 mg/kg, and by increased incidences of two skeletal variations (absent or poorly ossified supraoccipital and sternebrae) at 200 and 300 mg/kg. Thus, the maternal and developmental no-observed-adverse-effect level was 50 mg/kg/day. The time course disposition of [14C]DMF was examined over a 48-hr period in GD12- and GD18-pregnant rats after a single oral dose of 100 mg [14C]DMF/kg. Peak concentrations of radiocarbon occurred within 1 hr after dosing. Embryonic (GD12) and fetal (GD18) tissues accounted for 0.15 and 6% of the administered dose, respectively. Levels of radiocarbon in embryonic and fetal tissues were equal or slightly less than in maternal plasma up to 8 and 24 hr, respectively, and higher thereafter. HPLC analysis performed at intervals from 1 to 8 hr on GD12 and 1-24 hr on GD18 indicated that unchanged DMF and metabolites were readily transferred to the embryonic and fetal tissues, where their levels were generally equal to those in maternal plasma. The parent compound accounted for most of the radioactivity until 4-8 hr and then decreased. N-Hydroxymethyl-N-methylformamide (HMMF) and N-methylformamide (NMF) were the predominent metabolites and increased with time. Much lower concentrations were found for formamide and N-acetyl-S-(N-methylcarbamoyl)cysteine. Transfer of radioactivity into milk was studied in dams given a single oral administration of 100 mg [14C]DMF on Lactation Day 14. DMF, HMMF, and NMF were found in the milk at concentrations equal to those in plasma.

Boric acid (BA), an ingredient of many pharmaceutical, cosmetic, and pesticide products, was previously shown to induce reproductive and developmental toxicity in laboratory rodents. In this study, BA (0, 62.5, 125, or 250 mg/kg/day, po) was administered on Gestational Days (GD) 6-19 to New Zealand White rabbits (18-23 pregnant/group). Maternal body weight, food consumption, and clinical condition were monitored at regular intervals throughout gestation. At termination (GD 30), the numbers of uterine implantations, resorptions, dead fetuses, and live fetuses were determined. Fetuses were weighed, and live fetuses examined for external, visceral, and skeletal defects. Maternal food intake decreased during treatment at 250 mg/kg/day and increased at s= 125 mg/kg/day after treatment. Maternal body weight (GD 930), weight gain during treatment, gravid uterine weight, and number of ovarian corpora lutea decreased at 250 mg/kg/day. In contrast, maternal corrected gestational weight gain increased at s= 125 mg/kg/day. Maternal liver weight was not affected. Relative (but not absolute) maternal kidney weight increased at 250 mg/ kg/day, and microscopic evaluation revealed no treatment-related renal pathology. At 250 mg/kg/day, prenatal mortality was increased (90% resorptions/litter vs 6% for controls), the proportion of pregnant females with no live fetuses was increased (73% vs 0%), and live litter size was reduced (2.3 fetuses/litter vs 8.8). As a result, there were only 14 live fetuses (6 live litters) available for evaluation in the high-dose group, compared to 153-175 live fetuses (18-23 live litters) in the other groups. The percentage malformed fetuses/litter was increased at 250 mg/kg/day, primarily due to cardiovascular defects in 72% of high-dose fetuses vs 3% The U.S. Government's right to retain a nonexclusive royalty-free license in and to the copyright covering this paper, for governmental purposes, is acknowledged. 1 Presented in part at the 31 st Annual Meeting of the Society of Toxicology, Seattle, WA, February 23-27, 1992 (Price el ai, 1992), and at the International Symposium on the Health Effects of Boron and Its Compounds, Irvine, CA, September 16-17, 1992 (Heindel et al., 1994). 2 To whom all correspondence should be addressed. 3 Present address: National Center for Toxicological Research (NCTR), HFT-1, 3900 NCTR Road, Jefferson, AR 72079-9502. of controls. The most prevalent cardiovascular malformation (interventricular septal defect) was observed in 57% of high-dose fetuses compared to 0.6% among controls. At 250 mg/kg/day, average fetal body weight/litter was 92% of the average control weight (not statistically significant). In summary, no definitive maternal or developmental toxicity was observed at 62.5 or 125 mg/kg/day BA. Mild maternal effects and severe developmental toxicity were Observed at 250 mg/kg/day. © 1996 Society of Toxicology.

Ethylene glycol (EG) is a major industrial chemical, shown to be teratogenic at high doses by gavage in rodents. Since one route of industrial exposure is to the aerosol at high concentrations, timed-pregnant CD rats and CD-1 mice were exposed, whole-body, to a respirable aerosol of EG (mass median aerodynamic diameter, 2.3 microns) on Gestational Days (GD) 6 through 15 for 6 hr per day at target exposure concentrations of 0, 150, 1000, or 2500 mg/m3 (analytical concentrations of 0, 119 +/- 13, 888 +/- 149, and 2090 +/- 244 mg/m3, respectively), with 25 plug-positive animals per species per group. Clinical observations and maternal body weights were documented throughout gestation for both species. Maternal food and water consumption was measured in rats only throughout gestation. At scheduled necropsy (GD 21 for rats, GD 18 for mice), maternal animals were evaluated for body weight, liver weight, kidney weight, gravid uterine weight, number of ovarian corpora lutea, and status of implantation sites, i.e., resorptions, dead fetuses, live fetuses. Fetuses were dissected from the uterus, counted, weighed, sexed, and examined for external, visceral, and skeletal malformations and variations. All rat dams survived to scheduled termination. Minimal maternal toxicity was indicated by a significant increase in absolute and relative liver weight at 2500 mg/m3. Food and water consumption, maternal body weights and weight gain, and maternal organ weights (other than liver) were unaffected by exposure. Gestational parameters were unaffected by exposure, including pre- and post-implantation loss, live fetuses/litter, sex ratio, and fetal body weight/litter. There was no treatment-related increase in the incidence of any individual malformation, in the incidence of pooled external, visceral, or skeletal malformations, or in the incidence of total malformations by fetus or by litter. There were no increases in the incidence of external or visceral variations. Evidence of fetotoxicity, expressed as reduced ossification in the humerus, the zygomatic arch, and the metatarsals and proximal phalanges of the hind-limb, was observed at 1000 and 2500 mg/m3. All mouse dams survived to scheduled termination. One dam at 2500 mg/m3 was carrying a totally resorbed litter at termination. Maternal toxicity was observed at 1000 and 2500 mg/m3, expressed as reduced body weight and weight gain during and after the exposure period, and reduced gravid uterine weight. (Maternal effects may have been due, in part or whole, to effects on the conceptuses; see below.)(ABSTRACT TRUNCATED AT 400 WORDS)

Sprague-Dawley rats and Swiss (CD-1) mice were exposed to 0, 600, 1800, or 5000 ppm THF (a four-carbon cyclic ether, widely used as an industrial solvent) vapors, 6 hr/day, 7 days/week (6-19 days of gestation (DG) for rats; 6-17 DG for mice). Body weights of pregnant rats in the 5000 ppm group were reduced at euthanization. There were no effects on the percentage of live rat fetuses/litter or on the fetal sex ratio. Fetal body weight was significantly reduced for the 5000 ppm group, but the incidence of abnormalities was not increased. Mice in the 1800 and 5000 ppm groups were sedated during exposure; approximately 27% of the mice in the 5000 ppm group died. Mean body and uterine weights of mice were reduced for the 1800 and 5000 ppm groups at euthanization (18 DG), but adjusted maternal weight gain was not affected at 1800 ppm. There was a reduction in the percentage of live fetuses/litter for the mice in 1800 and 5000 ppm groups (95% resorptions in the 5000 ppm group). Fetal weight and sex ratio in mice were not affected. An increase in the incidence of reduced sternebral ossifications was correlated to THF concentration, although differences between groups were not statistically significant. There were no increases in the incidences of other malformations or variations. These results suggest that THF may be embryotoxic in mice, but if the conceptus survives, development as assessed by this experimental design continues in a normal fashion. The no-observable-adverse-effect level (NOAEL) for maternal toxicity was 1800 ppm in both rats and mice. The NOAEL for developmental toxicity was 1800 ppm in rats and 600 ppm in mice.

The teratogenic potential of a versatile solvent, N-formylpiperidine (NFP), was evaluated in the rat. Three groups of 25 mated female Sprague-Dawley rats were given 110, 220, or 440 mg/kg/day NFP in distilled water by gavage on Days 6 through 20 of gestation. A control group of 25 animals received distilled water on a comparable regimen. Maternal animals were observed daily for signs of toxicity; body weights and food consumption were measured at regular intervals throughout the study. All animals were euthanized on Gestation Day 21 and the fetuses examined for cleft palate and external abnormalities. One-half of the fetuses in each litter were examined for visceral anomalies while the remaining fetuses were examined for skeletal malformations after appropriate staining. One female in the high dosage group died on Gestation Day 12. Clinical signs of toxicity, observed in 6 females in the high dosage group, included tremors, convulsive movements, and an apparent weakness of the legs. Maternal toxicity, in terms of significantly decreased body weight and food consumption, was observed in the mid and high dosage groups. Food consumption was also significantly depressed for the first 4 days of dosing in the low dosage group. There was a significant increase in number of resorptions in the high dosage group when compared to controls. No effects were observed on other reproductive parameters. Mean fetal body weight was significantly lower in the high dosage group when compared to controls. While the incidence of fetal malformations on a litter basis was higher in the high dosage group, this change was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Methoxyethanol (2-ME) was applied as a single dermal dose on the backs of collared, pregnant Sprague-Dawley rats on Gestation Days (GD) 10, 11, 12, 13, or 14 at doses of 0 and 2000 mg/kg, and at doses of 0, 250, 500, and 1000 mg/kg on GD 12. Except for a transient loss in body weight observed the day after 2-ME administration, no signs of maternal toxicity were observed. On GD 20, dams were necropsied and the fetuses evaluated for normal development. Resorptions were significantly (p less than 0.05) increased in dams exposed to 2-ME on GD 10. Fetal body weights were reduced at dose levels of 1000 and 2000 mg/kg, but statistically significant differences were found only on GD 10 and 12. Significant increases in external, visceral, and skeletal malformations were observed in fetuses exposed to 2-ME at dose levels of 500 mg/kg or greater. Defects of the cardiovascular and urinary systems were the prominent visceral malformations observed. Limb defects (especially those pertaining to the digits) and vertebral column defects (primarily of the tail) were the most frequently observed skeletal defects. At the 2000 mg/kg dose level, 2-ME was teratogenic regardless of the GD of administration. Based on the results of this study, the no observed adverse effect level for developmental toxicity for a single dermal dose of 2-ME applied on GD 12 was determined to be 250 mg/kg.

Diethylene glycol monomethyl ether (diEGME) was one of 15 glycols tested in CD-1 mice using a short-term in vivo reproductive toxicity assay (Chernoff/Kavlock test). Because results were strongly suggestive of potential reproductive toxicity, a teratology study was conducted in Sprague-Dawley rats. Time-mated females were orally dosed on Days 7-16 of gestation with diEGME in distilled water. Doses of 0, 1000, 1495, 2235, 3345, and 5175 mg/kg/day were used in a preliminary dose-finding study. At 5175 mg/kg/day, two of nine rats died, five of five litters were totally resorbed, and maternal extra gestational body weight gain was reduced. At 3345 mg/kg/day, six of nine litters were resorbed but there were no deaths and extra gestational body weight gain was not affected. Visceral and skeletal examinations revealed a dose-related increase in malformations, primarily of the ribs and cardiovascular system. Subsequently, pregnant rats were similarly dosed with 0, 720, or 2165 mg/kg/day. Neither dose was maternally toxic, but fetal body weights and the number of live implantations were significantly reduced at 2165 mg/kg/day. Rib malformations were seen in 9.1% (control), 42.9% (720 mg/kg/day, p less than 0.05), and 80.0% (2165 mg/kg/day, p less than 0.001) of litters. Cardiovascular malformations occurred in 0.0, 4.8, and 71.4% (p less than 0.001) of litters. Diethylene glycol monomethyl ether thus was teratogenic in rats at all doses tested, producing a dose-dependent series of malformations similar to those produced by other members of the glycol ether family.

The developmental toxicity (embryofetotoxicity or teratogenicity) and maternal toxicity of butoxypropanol, a propylene glycol ether, was evaluated in New Zealand White rabbits. Dosages of 0 (water), 10, 40 or 100 mg/kg/day, selected on the basis of the water solubility of butoxypropanol and the results of a pilot study, were administered percutaneously to groups of artificially inseminated (Day 0) female rabbits on Days 7 through 18 of gestation. The dosage volume was 2 ml/kg. The control group contained 17 does and each test group contained 19 does. Does were observed for signs of test substance effect on abortion or premature delivery, body weight, and feed consumption. On Day 29, they were euthanized and examined for pregnancy, number and placement of implantations, early and late resorptions, and live fetuses. Pregnancy occurred in 15 control does (88%) and in 16 does in each test group (84%). There were no statistically significant differences between test and control groups for maternal body weight gain, feed consumption, number of corpora lutea per ovary, implantations, live fetuses, early and late resorptions, fetal body weights, gender, or gross external changes. There were no visceral or skeletal fetal alterations at any dose tested. No signs of maternal toxicity were observed; however, mild erythema occurred at the site of application at the 100 mg/kg/day dose level. The developmental no-effect level was greater than 100 mg/kg/day.