The postnatal effects of prenatal exposure to low doses of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) in Sprague-Dawley rats

Nitrofen was administered to pregnant Sprague-Dawley rats by gavage on days 8-16 of gestation at 5 different dose levels--0, 0.46, 1.39, 4.17 and 12.5 mg/kg/day. Diaphragmatic hernias were found in pups that died immediately after birth at the 3 highest dose levels. At the 1.39-mg/kg dose level 3 of the 4 pups examined had diaphragmatic hernias, at the 4.17-mg/kg dose level 2 out of 3 pups had diaphragmatic hernias, and at the 12.5-mg/kg dose level all 5 pups found dead had diaphragmatic hernias. Locomotor activity of the offspring was measured on postnatal days 17 and 24, and hyperactivity was evident at the 3 highest dose levels. However, when the rats were later tested at 45, 49 and 90 days of age they had apparently recovered from this earlier hyperactivity. In the female rat, nitrofen did not delay the onset of puberty as measured by the age of vaginal opening or the age at first estrus. At necropsy of the offspring which began on postnatal day 133, Harderian gland weight reduction and hydronephrosis were seen at the 4.17- and 12.5-mg/kg dose levels, while no effects were found in body, liver, testes, seminal vesicle, kidney, or lung weights. Results of the present study and earlier studies demonstrate that rats are more sensitive than mice to the teratogenic effect of nitrofen (Gray et al., Science, 215 (1982) 293 and Gray et al., Toxicol. Appl. Pharmacol., 67 (1983) 1). In general, nitrofen affects the same organ systems in rats as it does in mice, but the rank order of sensitivity of these effects differs from those described earlier in the mouse by Gray et al. (Toxicol. Appl. Pharmacol., 67 (1983) 1).

The effect of acute maternal toxicity on fetal development in the mouse

The effects of acute alterations in maternal health status upon fetal development were assessed following exposure of pregnant CD-1 mice on day 8 of gestation to one of ten chemicals at doses calculated to exert either a low or a moderate degree of maternal lethality. The dams were killed on day 18 of gestation, and the fetuses were examined by routine teratological techniques. The chemicals were cacodylic acid, caffeine, deltamethrin, dinoseb, ethylene bisisothiocyanate sulfide (EBIS), endrin, guthion, kepone, sodium salicylate, and toxaphene. Three (cacodylic acid, EBIS, and kepone) produced dose-related increases in the incidence of dams with completely resorbed litters. Prenatal mortality in litters that contained live fetuses at term was elevated only for one chemical (cacodylic acid). Fetal weight was reduced in three instances (cacodylic acid, endrin, and guthion), while the incidence of terata was markedly elevated for two (cacodylic acid and kepone). For two other chemicals (endrin and sodium salicylate), a low incidence was found of defects that were similar to defects induced by those chemicals in other species. These effects appear to be chemospecific in nature and not the result of some indirect maternal action. Thus, maternal health status, as measured by the incidence of lethality in the treated groups and by the magnitude of maternal weight gain in surviving females, presents no simple explanation for many manifestations of fetal toxicity. However, for seven chemicals (excluding deltamethrin, EBIS, and kepone) an increased incidence of supernumerary ribs was observed. For three of these seven chemicals (caffeine, dinoseb, and toxaphene), supernumerary ribs was the only observed fetal effect. There was a significant linear inverse relationship between maternal weight gain during gestation and the incidence of extra ribs in the treated groups compared to their respective controls. Under the experimental conditions of this study, it appears that the incidence of supernumerary ribs increased in response to a nonspecific maternal toxicity.

Toxicity of mercuric chloride to the developing rat kidney. II. Effect of increased dosages on renal function in suckling pups

It has been demonstrated that the sensitivity to HgCl2 nephrotoxicity increases with maturity in the rat, and that neonates are largely unaffected by a dose of 5 mg/kg. In the present study, immature rat pups were exposed to higher doses of HgCl2 to determine whether this effect was attributable to a quantitative or qualitative difference in the renal sensitivity to HgCl2. Sprague-Dawley rats were injected with a single dose of 5, 7.5, 10, 12.5, 20, or 30 mg/kg on Postnatal Day 1; 5, 7.5, 10, 12.5, 15, or 20 mg/kg on Day 8; or 6.25, 7.5, 10, or 12.5 mg/kg on Day 15. Renal function was evaluated at 24, 48, and 120 hr after treatment by measuring urine volume, osmolality, urinary pH, and chloride content, the ability to concentrate urine during water deprivation, and the presence of protein, glucose, or hemoglobin in urine. Animals were then killed and their kidneys weighed. A dose of 20 mg/kg was needed to induce mortality in pups treated at 1 day of age, and 15 mg/kg was needed in pups treated at 8 days of age. In contrast, the 6.25-mg/kg dose given to 15-day-old pups produced some mortality, and all rats given higher doses at 15 days of age died within 2 days. There was marked oliguria or anuria in the rats that died. Kidney weight was increased in a dose-related fashion at all ages. In those animals not rendered oliguric by the treatment, urine volume increased and the ability to secrete a more concentrated urine during water deprivation decreased. Urinary pH was decreased in a dose-related manner. Urinary chloride excretion was temporarily decreased after HgCl2 treatment on Day 1 , but was increased thereafter. Proteinuria, glucosuria, and hematuria were detected in the treated rats, again increasing in frequency and severity with age and dose.

An extended evaluation of an in vivo teratology screen utilizing postnatal growth and viability in the mouse

A teratology test system proposed by Chernoff and Kavlock utilizes growth and viability for 3 days after birth to prioritize chemicals for standard teratology testing. The present study is an extended observation of the growth and viability of Chernoff and Kavlock's animals from 41 treatments for 250 days to determine if neonatal weight reductions persisted throughout life, if mortality occurred later in life or, if other serious abnormalities developed that could not be anticipated from the neonatal data. One chemical which was positive in the present study would be a false negative in the standard teratology test and the Chernoff/Kavlock Assay (CKA). Congo red did not cause frank malformations or mortality but it specifically altered reproductive function in the offspring. Two chemicals produced a variety of unusual abnormalities that were not apparent in the neonates, indicating that postnatal testing is necessary to determine the full teratogenic potential of some compounds. Mice exposed prenatally to cytosine arabinoside became hydrocephalic and 30% of them lacked lower incisors. Nitrofen caused hydrocephaly, the age of eye-opening was delayed, a few of the mice had no eyes, and most of the mice lacked Harderian glands. Eighteen of the 41 treatments caused mortality of 15%, or greater, by day 3, and four of these treatments resulted in additional mortality past the neonatal period. No compound caused a decrease in viability after the neonatal period without also reducing days 1 or 3 litter sizes, validating the use of this measurement in the CKA. Cytosine arabinoside was administered later in gestation than the CKA dosing regime and caused a marginally significant increase in mortality near birth but killed over 50% of the pups after weaning. Altering the duration or period of exposure in the CKA may necessitate a longer postnatal evaluation than presently recommended. Neonatal weight, the second parameter used in the CKA to prioritize chemicals for additional testing, appears to be less useful than viability. It was a poor predictor of subsequent growth, some early weight effects persisted, while most of those concurrent with maternal weight reductions were transient. A correlation analysis of the parameters measured in the CKA and in the present study, excluding the compounds that produce frank malformations, indicated that compounds that reduced maternal weight gain during dosing had fewer live pups and growth was transiently retarded.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrocardiographic responses of rat fetuses with clamped or intact umbilical cords to acute maternal uterine ischemia

Uterine ischemia results in severe cardiac disturbances in the fetus. It has been postulated that these effects are due to interaction between the fetus and the ischemic uterus or placenta, and not to hypoxia or buildup of metabolites in the fetus. Rat fetal cardiac responses to uterine clamping and umbilical cord clamping were compared by electrocardiography. On day 21 of gestation, fetuses in a total of 14 pregnant rats were exposed to umbilical clamping, uterine clamping, or no clamping. Electrocardiograms were recorded for each fetus immediately after clamping and at 10, 20, and 30 minutes after clamping. Immediately after clamping, the uterine clamping group alone showed severe sinus bradycardia. At all other observation times, fetuses exposed to uterine or umbilical clamping showed bradycardia and other electrocardiographic changes typically associated with hypoxia. Therefore, umbilical clamping protected the fetuses from the adverse effects of uterine clamping for only a very short time.

Toxicity of mercuric chloride to the developing rat kidney. I. Postnatal ontogeny of renal sensitivity

Although the sensitivity of the adult rat kidney to mercuric chloride has been widely reported, the degree to which this toxicant affects the developing kidney is unknown. Therefore, this study examined the effects of HgCl2 on renal function during postnatal maturation. Sprague-Dawley rats were treated with a single sc injection of 5 mg/kg HgCl2 on Day 1, 8, 15, 22, or 29 after birth. The effects on renal function, histology, and morphology were assessed 24, 48, and 120 hr after each treatment. Measurements of renal function included urine volume, osmolality, the ability to concentrate urine during water deprivation, urinary pH, chloride and protein content, tests for glucosuria, hematuria, and various serum chemistry parameters. Rats were killed and their kidneys processed and examined by light microscopy. The renal sensitivity to HgCl2 increased throughout maturation for every parameter measured. No pups treated with HgCl2 on Day 1 died, but mortality increased to almost 20% in rats treated 22 and 29 days after birth. Body weight was unaffected in Day 1 animals, but was decreased at 120 hr post-treatment in three of the other four age groups. Kidney weights were unaffected in 1- and 8-day olds, but were increased by 10 to 55% in rats that were 15, 22, and 29 days old. Urine volume was increased 48 to 72 hr following treatment at all ages. The ability to concentrate urine in response to water deprivation was compromised in all animals with the exception of those treated on Day 1, and was decreased to the greatest extent in 29-day-olds. Urinary chloride concentration was decreased in Day-22 animals at 24 and 48 hr, and in Day-29 rats at all times observed after injection. Urinary pH was more acidic in treated suckling pups, and more basic in treated pups after weaning on Day 22. Urinary protein content was increased after exposure in all but the pups treated on Day 1. Serum creatinine was increased at 120 hr after injection in Day-8 rats, and 24 and 48 hr after injection in older rats. Glucosuria and hematuria occurred with increasing frequency as the pups matured. Histological evaluation revealed some cortical tubular dilatation in rats treated on Day 1 or Day 8; there was tubular necrosis in older rats. For all parameters observed, the neonatal kidney was largely insensitive to HgCl2 toxicity; however, a trend toward increased sensitivity with increasing age was demonstrated.

Postnatal evaluation of morphological and functional effects of prenatal exposure to nitrofen in the Long-Evans rat

The herbicide Nitrofen was administered to Long-Evans rats on d 11 of gestation (75 mg/kg, po) in an effort to further evaluate its reported ability to induce hydronephrosis and to affect Harderian-gland development. This regimen did not affect the litter size at birth or postnatal growth and viability. Eye opening, recorded on postnatal d 16 (PD 16), figure-eight maze activity (PD 24), and vaginal opening (PD 31) were unaffected by treatment. Lung weights were lower on PD 7 and 35 but not at PD 210. Harderian-gland weights were lower at PD 35 and 210, and 12% of the Nitrofen-treated offspring had missing glands, versus 0% of controls. Hydronephrosis was detected in 23% of the necropsied offspring and was represented in every treated litter. Only one control pup (1.5%) was hydronephrotic at necropsy. Treated pups, regardless of the presence or absence of hydronephrosis, had a diminished ability to concentrate urine in fluid deprivation tests applied on PD 3 and 6. By PD 50, however, treated offspring were not deficient in a similar test unless hydronephrosis was present. Microscopic examination on PD 7 of morphologically normal kidneys showed no treatment-related delay in nephrogenesis. Serum chemistry values evaluated at PD 210 showed no overall treatment effect, but animals with hydronephrosis had elevated phosphorus, urea nitrogen, creatinine, and potassium levels. This study has demonstrated that a single prenatal exposure to Nitrofen alters Harderian-gland development, lung growth, and renal development and function. Hydropenia tests applied to neonates detected renal dysfunction and were predictive of hydronephrosis, while a similar test in young adults did not detect dysfunction in morphologically normal animals. The neonatal hydropenia test appears to be an extremely useful tool in evaluating perinatally induced renal dysfunction.

The effects of the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether (NIT) on serum thyroid hormones in adult female mice

The administration of the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen; NIT) to adult female mice by i.p. injection at doses of 500 and 1000 mg/kg/day for 3 days, reduced serum thyroxine (T4) levels. T4 levels were reduced in the high-dosage group by 60% of the control and by 20% in the low-dose group. Serum triiodothyronine (T3) levels were relatively unaffected by NIT treatment at either dose. The animals appeared euthyroid, as body weights were unaffected even though T4 levels were reduced. Liver weights were slightly higher as a result of NIT exposure at both 500 and 1000 mg/kg/day.

Postnatal developmental alterations following prenatal exposure to the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether: a dose response evaluation in the mouse

Although nitrofen, 2,4-dichlorophenyl-p-nitrophenyl ether, is a relatively nontoxic herbicide, prenatal exposure to doses considerably less than the LD50 value for adult rats and mice produces numerous developmental defects that become apparent as the animals mature. In the present study postnatal development was observed following prenatal exposure during Days 7 to 17 of gestation at doses of 0, 6.25, 12.5, 25, 50, 100, 150, and 200 mg/kg/day. These doses did not cause maternal toxicity as indicated by the viability of the dams or maternal weight gain during pregnancy. By 3 days of age all pups in the two highest dose groups were dead and 50% had died in the 100 mg/kg/day dose group. Some of the dead and moribund pups from the 200 mg/kg/day exposure group necropsied at three days of age had cleft palate (15%) or diaphragmatic hernia (6%). In addition, about 22% of the pups at 200 mg/kg/day developed a distended abdomen from gasping and swallowing air. These pups did not suckle and eventually died. Body weights of offspring were reduced at birth in the 150 and 200 mg/kg/day groups and at 3 days of age in the 100 mg/kg/day group. Growth rates were subsequently retarded at 12.5, 25, 50, and 100 mg/kg. The Harderian glands were reduced or absent in 97, 65, and 4% of the mice in the 100, 50, and 25 mg/kg dosage groups, respectively, and the gland weights were reduced at all dosages, including the lowest dose of 6.25 mg/kg/day. Weights of other organs including lung and liver (at 6.25 and above), seminal vesicle (at 12.5 and above), and testes (at 100 mg/kg/day) were also reduced by prenatal nitrofen exposure. In addition, prenatal treatment with nitrofen produced functional deficits of the reproductive system; puberty was delayed in females and litter sizes were reduced at 50 and 100 mg/kg/day. A cross-fostering experiment with 100 mg/kg/day of nitrofen demonstrated that the effects noted in the present study were produced solely by prenatal exposure; pups exposed to nitrofen in the milk alone as a consequence of any accumulation of nitrofen in the dam during gestation were unaffected.

Morphometric, biochemical, and physiological assessment of perinatally induced renal dysfunction

Three chemicals, known either to alter renal development when administered during fetal development or to affect renal function when administered to adult rats, were administered to Sprague-Dawley rats at critical periods of renal development. Chlorambucil (CHL) was administered ip on d 11 of gestation at doses of 0, 3, and 6 mg/kg; nitrofen (2,4-dichlorophenyl p-nitrophenyl ether) (NIT) was given po on d 8-16 of gestation at 0, 4.17, 12.5, and 25 mg/kg . d; and mercuric chloride (MER) was given sc on postnatal d 1 at 0, 14, and 28 micrograms/pup. To assess the effects of these toxicants on the functional development of the kidneys, a diuresis test with and without antidiuretic hormone was applied on postnatal d 3 (PD 3); a hydropenia test on PD 6; and kidney weights, glomerular counts in midhilar cross sections, and the specific activity of renal alkaline phosphatase were determined on PD 3 and 6. Data from pups with obvious malformations of the kidneys was eliminated from the statistical analyses of the data so that emphasis could be placed on alterations of functional development in individuals with apparently morphologically normal kidneys. CHL retarded the growth and biochemical differentiation of the kidney at 6 mg/kg. Pups from this treatment groups showed an attenuated response to exogenously administered antidiuretic hormone. NIT impaired growth and altered renal morphology at a dose of 12.5 mg/kg . d and altered physiological responses in the absence of anatomical changes at a dose of 4.17 mg/kg . d. MER, at doses near the maximum tolerated, failed to alter any parameter, indicating that the very young animal differs markedly from the adult in response to that compound. The data indicate that relatively simple tests of renal function are useful in the detection of perinatally induced nephrotoxicity.

An in vivo teratology screen utilizing pregnant mice

Twenty-eight compounds of known teratogenic potential were assayed by an in vivo screening procedure. Postnatal growth and viability of prenatally exposed offspring was used as a measure of developmental toxicity. Gravid CD-1 mice were administered maximum tolerated doses of the compounds for up to 5 consecutive days during the period of major organogenesis. The dams were allowed to give birth, and litter size and weight on postpartum d 1 and 3 were recorded and compared with concurrent controls. All 15 compounds that were teratogenic by standard teratology test criteria exhibited some form of developmental toxicity. Four chemicals known to produce only fetal toxicity (reduced weight or supernumerary ribs) were tested and the screen successfully identified those that reduced weight. Finally, of the 9 compounds that show no effect in standard tests, 6 were also negative in the screen and 3 demonstrated either reduced viability or weight.

An analysis of fetotoxicity using biochemical endpoints of organ differentiation

The biochemical differentiation of the brain, lungs, liver, and kidneys of the late gestation rat fetus was examined to characterize the immediate implications of retarded growth on fetal development. Initially, the normative profile of development of the brain (weight, DNA content, and protein content), lungs (weight and surfactant accumulation), liver (weight and glycogen deposition), and kidneys (weight, alkaline phosphatase activity, and protein content) was determined on gestation days 19, 20, 21, and 22 (day 1 = finding of sperm in the vaginal smear). Subsequently, five compounds known to induce fetotoxicity (chlorambucil, methyl salicylate, mirex, nitrofen, and toxaphene) were administered during organogenesis, and the effects on organ differentiation were determined in day 21 fetuses. The effects of fetal growth retardation resulting from exposure to exogenous agents were not equally distributed among the organs studied. The liver and kidney appeared more sensitive to insult by these agents than did the brain and lungs.

Prenatal exposure to the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether destroys the rodent Harderian gland

Exposure of mice to the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether during gestation produces abnormalities that are not readily apparent at birth but become obvious as the pups mature. By 2 weeks after birth there are severe intraorbital defects resulting from destruction of the Harderian glands behind the eyes. This effect is noticeable only postnatally because the Harderian gland does not grow or function until after birth.

Evaluation of renal function in neonatal rats

The ontogenetic profile of several parameters of neonatal renal development in the rat is presented. Nephrogenesis was observed to continue at a rapid pace between birth and 8 days of age and to be virtually complete by 11 days of age. The activity of alkaline phosphatase, a brush border enzyme, declined during this time period relative to organ growth as a whole. The ability to elaborate a concentrated urine when presented with a period of fluid deprivation was barely present at birth and increased dramatically with age. Finally, the diuresis response to an orally administered water load was detected on the second postnatal day, while the response to antidiuretic hormones was present to a slight degree on the first postnatal day.

Multigeneration study of 1,2,4-trichlorobenzene in rats

Rats were continuously exposed to 0, 25, 100, or 400 ppm 1,2,4-trichlorobenzene (TCB) in the drinking water, beginning with birth of the F0 generation and continuing through weaning of the F2 generation. The treatment did not affect fertility, growth, viability, locomotor activity, or blood chemical analysis. Adrenal gland enlargement was observed in both the F0 and F1 animals at 95 d of age. To further examine the adrenal enlargement found in the reproduction study, an acute toxicity study was undertaken in which immature females were given ip injections of 0, 250, or 500 mg/kg TCB on 3 consecutive days. It was found that TCB had no estrogenic activity and that the livers and adrenals of treated females were significantly larger than those of controls. Rather than being estrogenic, TCB in this treatment regimen resulted in a decrease in uterine weight. These two studies demonstrate that chronic or acute doses of TCB can produce adrenal enlargement in rats.

Perinatal toxicity of endrin in rodents. II. Fetotoxic effects of prenatal exposure in rats and mice

The fetotoxic potential of endrin in the CD rat and CD-1 mouse was investigated. Endrin was administered as a solution in corn oil to groups of pregnant animals by gastric intubation at multiple dose levels throughout the period of organogenesis. The dams were sacrificed prior to term and the fetuses were examined for skeletal and visceral anomalies. In addition, maternal livers and fetuses from rats in each dose level were analyzed for endrin content. In the mouse, endrin caused maternal liver enlargement at a dose of 0.5 mg/kg/day and reduced maternal weight gain at a dose of 1.0 mg/kg/day. Fetal weight and skeletal and visceral maturity were adversely affected at a dose of 1.0 mg/kg/day, but no teratogenic effect or embryo lethality was evident even at a dose level that produced maternal lethality (1.5 mg/kg/day). In the rat, endrin markedly reduced maternal weight at doses above 0.150 mg/kg/day but produced no apparent effects on the fetus. The data suggest that species differences in sensitivity to endrin may in part be due to differences in metabolism. Although endrin levels in rat fetuses at a maximally tolerated dosage level resembled those previously reported for the hamster, relatively less 12-ketoendrin was present, paralleling the change in fetal sensitivity.

Perinatal toxicity of endrin in rodents. III. Alterations of behavioral ontogeny

The behavioral development of rats and hamsters was observed following perinatal exposure to endrin, a central nervous system teratogen in the hamster but not the rat [1,2]. In the hamster, prenatal exposure to endrin at 1.5 mg/kg/day on days 5-14 of gestation produced a persistent elevation in the locomotor activity. Offspring of treated hamsters ambulated 75% more than controls in the open field at 15 days and 45% more at 20 days of age. Long term observations of locomotor activity in the figure-8 mazes indicated that a significant elevation of this behavior was still present at 125 days of age. Non-locomotor behaviors of the Offspring (including sexual, rearing and running wheel behaviors) were unaffected. The dams repeatedly exposed daily to endrin at 0.75 or 1.5 mg/kg/day were markedly hypoactive using the same testing conditions in which the pups were hyperactive. This dosing regime was toxic to the dams in the 1.5 mg/kg/day dose group, killing more than half of them. In the second experiment, rats exposed perinatally to endrin at 0.15 or 0.30 mg/kg/day were 30% more active than control prior to weaning, but not as adults. These doses did not kill dams or affect the pup survival or growth. The similarity of the behavioral changes noted in the young of both species is suggestive of similar alteration of central nervous system function even though endrin produces gross morphological defects only in the hamster.

The teratogenic potential of cacodylic acid in the rat and mouse

Cacodylic acid, an organic arsenical herbicide, was administered to time-pregnant albino CD rats and CD-1 mice on days 7-16 of gestation. The compound was given by gastric intubation as a solution in distilled water. Rats received 0, 7.5, 15, 30, 40, 50, or 60 mg/kg/day in 0.2 ml/day intubation volume; mice received 0, 200, 400, or 600 mg/kg/day in 0.1 ml/day. Following maternal sacrifice on day 18 (mice) and 21 (rats), fetuses were weighed and fixed for skeletal and visceral examinations. Fetal and maternal toxicity was observed in both species. In the mouse, maternal toxicity was evident at the lowest dose, while teratogenic response was confined to cleft palate at 400 and 600 mg/kg/day. The effective maternal toxic dose in the rat was 40 mg/kg/day. In this species, incidence of irregular palatine rugae, i.e., ridges that were discontinuous and/or not lying in apposition at the palatal raphe, was significantly (p less than 0.001) dose-related. The results suggest an "apparent no effect level" for this anomaly below 30 mg/kg/day.

Studies on the developmental toxicity of ozone: postnatal effects

Pregnant rats were exposed to either 0, 1.0, or 1.5 ppm ozone during either mid gestation (Days 9-12) or late gestation (Days 17-20). The dams were allowed to deliver and the early morphological and behavioral development of their pups was monitored. Both exposure regimens transiently reduced neonatal growth rates. The late gestation exposure regimen produced retardations in early reflex development and in open field behavior. Finally, several males from this exposure regimen remained permanently stunted in growth.

Perinatal toxicity of maneb, ethylene thiourea, and ethylenebisisothiocyanate sulfide in rodents

The potential of the fungicide maneb and two of its metabolites, ethylenebisisothiocyanate sulfide (EBIS) and ethylene thiourea (ETU), to induce perinatal toxicity in four species of rodents was investigated. The compounds were admininistered to rats and mice during the period of organogenesis, and ETU was also administered to rats and mice during the period of organogenesis, and ETU was also administered by oral gavage for a similar period to hamsters and guinea pigs. Treatment also continued through the lactational period in groups of rats that were allowed to give birth. Fetuses were examined for signs of toxicity, including terata, and neonates for reflex developement and open-field behavior. Maneb produced hydrocephalus in fetuses in litters of rats receiving 480 mg/kg . d. No fetotoxic effects were noted in litters of rats receiving EBIS at doses at high as 30 mg/kg . d. ETU proved to be a potent teratogen in the rat. Among the effects seen at doses of 40 mg/kg . d or greater were hydrocephalus, encephalocele, kyphosis, and various defects of the digits. Neither maneb (up to 1500 mg/kg . d), ETU (up to 200 mg/kg . d), nor EBIS (up to 200 mg/kg . d) elicited signs of fetal toxicity in the mouse. ETU also failed to result in fetal toxicity when administered to the hamster (100 mg/kg . d) or the guinea pig (100 mg/kg . d). Neither maneb nor EBIS produced significant dose-related alterations in the behavioral development of perinatally exposed rat neonates. At doses that also produced neonatal hydrocephalus, ETU produced significant increases in the open-field activity of the neonates. In addition to the perinatal effects noted above, both maneb and EBIS caused maternal limb paralysis in the rat, an effect not noted in the mouse at much higher doses.

Perinatal toxicity of endrin in rodents. I. Fetotoxic effects of prenatal exposure in hamsters

The potential of the insecticide endrin to induce fetal toxicity was determined in hamsters exposed to the compound on either day 8 or days 5--14 of gestation. Endrin was administered by oral gavage as a solution in corn oil. Doses used included 0.5--10.0 mg/kg on day 8 and 0.75 to 3.5 mg/kg/day on days 5--14. Exposure to a single dose of endrin resulted in significant incidences of fused ribs and meningoencephaloceles at levels of 5 mg/kg or greater. No significant effects were noted in either maternal mortality and weight gain or in fetal mortality or weight gain. The administration of multiple doses of endrin resulted in few fetal defects, although a significant dose-related increase in fetal mortality and decrease in fetal weight was seen. Significant maternal lethality and weight reductions were noted at doses of 1.5 mg/kg/day or greater. At sacrifice, maternal liver and fetal tissues were collected and subsequently analyzed for endrin and a major metabolite, 12-ketoendrin. Endrin was found to cross the placenta and 20 ppb were found in fetuses from litters exposed to 2.5 mg/kg/day. Maternal livers from this dose group contained an average of 2500 pbb of endrin.