Evaluation of the teratogenic potential of the dopamine agonist bromocryptine in rats

Single subcutaneous injections of bromocryptine (BCR; 2 mg/kg) to rats on days 5, 7 or 10 of gestation caused a lowering of the serum prolactin (PRL) concentration and, on days up to and including day 8 of gestation, abortion of entire litters. Coincident with the end of the PRL-dependent phase of gestation (approximately day 9), BCR was no longer abortifacient, allowing higher doses of the drug to be administered from this time without the risk of abortion. Treatment at 50 or 100 mg/kg from day 10 to 16 of pregnancy, despite affecting the dams (increased water consumption), had no adverse effects on pregnancy or fetal development.     

Toxicological effects of cadmium during pregnancy in Wistar albino rats

Cadmium is a heavy metal and widespread environmental toxicant. This study investigated the effects of prenatal Cd exposure on fetal growth and limb development in rats. Pregnant rats were given 0, 4 or 8 mg/kg/day (equivalent to ≈ 0, 30 or 60 ppm) of cadmium as CdSO₄ in their drinking water from conception to gestation day 20. Cd significantly (p<0.001) and dose-dependently inhibited maternal weight gain and caused abortion of pregnancy. In addition, Cd significantly (p<0.001) decreased fetal body weight, forelimb and hindlimb bone lengths, compared to controls. These effects were sex-dependent, greater in the female offspring. Furthermore, there were reductions in the weights, and alterations in the histology of maternal placenta, ovary and liver of Cd-exposed rats. The results indicate that cadmium will cause abortion of pregnancy and sex-dependent impairment of fetal growth and limb development, which may be consequent upon alterations in ovarian and placental functions.     

Developmental toxicity study of chlorpyrifos in rats

Chlorpyrifos (O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)-phosphorothioate) was evaluated for potential developmental toxicity. Groups of 30 bred female Fischer 344 rats were given 0, 5, 15, and 25mg/kg per day by gavage on gestation days 6-15; the fetuses were evaluated on gestation day 21. Clinical signs of toxicity attributed to chlorpyrifos were noted in dams receiving 15 and 25mg/kg per day. Maternal effects in these groups also included depressed body weight and acetylcholinesterase activity. Fetal weight and viability were decreased, and fetal death and early resorption were increased at the 25mg/kg per day maternal dose. Visceral, skeletal, and external variations were also increased in this group. Chlorpyrifos showed fetotoxic and teratogenic effects at a maternal dose of 25mg/kg per day, a dose that also produced maternal toxicity.     

Effects of triphenyltin acetate on pregnancy in rats by oral administration

A teratological test was carried out on triphenyltin acetate (TPTA) used as a fungicide and antifouling agent. Pregnant Wistar rats were treated orally with TPTA at dose levels of 0, 1.5, 3.0, 6.0, 9.0 and 12.0 mg/kg/d during days 7-17 of gestation. Cesarean sections were performed on day 20 of gestation. In the pregnant rats, 2 of 13 and 2 of 12 dams died at 9.0 and 12.0 mg/kg, respectively. Vaginal bleeding, bloody mouth and nose, somnolence and depression of body weight gain and food intake were observed at 9.0 and 12.0 mg/kg at late stages of pregnancy. No statistically significant reductions in maternal thymus and spleen weights were observed on day 20 of gestation. Increase in embryonic and fetal deaths and in dams with total resorption of fetuses were observed at doses of more than 6.0 mg/kg. The doses of TPTA in this experiment, however, induced no teratogenic effects in rats.     

Evaluation of dimethoate toxicity on pregnancy in albino mice

We investigated whether dimethoate, an organophosphorus insecticide, causes abortion or fetal resorption in pregnant albino mice. Graded doses of 16, 20, 24, and 28 mg/kg body weight/d were administered orally from days 7 to day 15 of pregnancy. Laparotomy was performed on day 8 of pregnancy to note the number of implantations, and the animals were autopsied on day 19. The results revealed no inhibition of pregnancy in all dimethoate treated mice relative to a suitable control group. Treatment with 24 or 28 mg dimethoate caused a significant decrease in the number of implantations, live fetuses, and corpora lutea, but a decreased percent fetal survival and increased percent post-implantation loss and gestation length were not significant when compared with control mice. In all mice treated with 28 mg dimethoate, a significant decrease occurred in the body weight of the ovaries, uterus, and liver when compared with control mice. Following treatment with 16 or 20 mg dimethoate, however, no significant change was found in body and organ weights or in the number of implantations, live fetuses, and corpora lutea, percent post-implantation loss, and fetal survival, or gestation length compared with the corresponding parameters in control mice. The results of this study clearly indicate that dimethoate does not cause abortion or fetal resorption in pregnant mice. A significant decrease in the number of corpora lutea and percent fetal survival observed at higher doses of dimethoate could be due to a toxic effect on the embryo or to a hormonal imbalance.     

Reproduction studies with 1α,25-dihydroxyvitamin D3 (calcitriol) in rats and rabbits

Reproduction and teratology studies were performed in rats and rabbits with 1α,25-dihydroxyvitamin D₃ (calcitriol). Dosages of 0.02, 0.08, and 0.3 μg/kg/day were administered orally as a solution in Neobee oil. In rat teratology studies, no substantial differences were noted between control animals and animals treated with calcitriol from Days 7 through 15 of gestation with respect to litter sizes, resorption rates, pup weights, or external, visceral, and skeletal abnormalities. No adverse effects on either fertility or neonatal development were noted in rat reproduction studies in which male and female rats were pretreated prior to mating through sacrifice on Day 13 of gestation or through lactation Day 21. No adverse effect on perinatal development was noted in litters from females treated from Day 15 of gestation through Day 21 of lactation. However, hypercalcemia and hypophosphatemia were observed in treated pregnant female rats at dosages of 0.08 and 0.3 μg/kg/day and increased serum urea nitrogen was observed at 0.3 μg/kg/day. Hypercalcemia calcemia was noted in pups from dams receiving 0.08 and 0.3 μg/kg/day calcitriol. There was no decrease in the percentage bone ash as determined on lactation Day 21 in either treated females or their pups as compared to controls. In rabbits treated from Days 7 through 18 of gestation with 0.3 μg/kg/day, $\text{3}\text{16}$ rabbits died. Other signs of toxicity included maternal weight loss, an increased resorption rate and neonatal mortality. Two litters at 0.3 μg/kg/day and 1 litter at 0.08 μg/kg/day contained fetuses with multiple abnormalities. These studies demonstrated that in pregnant animals the observed effects of calcitriol are characteristic of those reported for vitamin D₃. In rabbits, dosages of 0.3 μg/kg/day calcitriol produced maternal and fetotoxic effects.     

Reproductive toxicity studies with cis-(-)-2,3,4,4a,5,9b-hexahydro-2,8-dimethyl-1H-pyrido-[4,3-b]indole dipalmitate in rats

cis-(-)-2,3,4,4a,5,9b-Hexahydro-2,8-dimethyl-1H-pyrido-[4,3-b]indole dipalmitate (stobadin dipalmitate; in the following briefly called STB) a new prospective cardioprotective drug, was evaluated for effects on fertility, general reproductive performance, prenatal and peri-postnatal development in the rat. Doses of 5, 15 and 50 mg/kg/d were administered orally in aqueous suspension to rats in all studies. Daily treatment of male rats for 70 days before mating and female rats for 14 days before mating and during gestation and lactation had no adverse effects on fertility, survival rate and weight gains of parental animals or on prenatal and postnatal development of pups. There was only evidence of slight adult toxicity late in the experiment, significant increase of anomalous foetuses in both the 15 and 50 mg/kg/d doses and decreased body weight of the young at 50 mg/kg/d on day 21 post partum. Daily oral treatment of pregnant rats with STB throughout organogenesis (day 4 to 16) had no overt effects on dams or on embryo-foetal development, except of increased incidence of some skeletal variations in all treated groups. In the peri-postnatal toxicity study treatment of pregnant dams with STB continuously from day 15 of gestation through parturition and lactation had no adverse effects on reproductive parameters of dams or on survival and development of F1 offspring at any dose used. There were only signs of slight maternal toxicity at 50 mg/kg/d, which consisted of sedated behaviour, reduced liver weight and reversible histopathological changes in kidney tissue. The results of these studies did not reveal serious developmental hazard potentials of STB administered to rats in doses up to 50 mg/kg/d.     

Teratology study in fischer 344 rats exposed to ethylene oxide by inhalation

Pregnant Fischer 344 rats were exposed 6 hr/day to either 100, 33, or 10 ppm of ethylene oxide vapor on Days 6 through 15 of the gestation period. Two separate control groups were maintained under the same conditions but were exposed to room air only. Two other groups of rats were given a known rodent teratogen, aspirin, by gavage; one group was given 500 mg/kg body weight on Day 9 of gestation, and the other was given 625 mg/kg body weight on Day 10 of gestation. No treatment-related effects of ethylene oxide were noted for the following evaluations; maternal survival, litter size, number of implantation and resorption sites, and number of preimplantation losses. Exposure to 100 ppm of ethylene oxide resulted in a significant depression of body weight in the fetuses, but did not result in any abnormal effects of embryonic or fetal lethality, or teratologic effects of the soft tissues or skeleton. Consequently, ethylene oxide was not considered a teratogen by inhalation in the Fischer 344 rat at an exposure concentration of 100 ppm.     

Maintenance or interruption of pregnancy by human chorionic gonadotrophin in adrenalectomized albino rats

In the present study, we investigated the efficacy of human chorionic gonadotrophin (HCG) in the maintenance of pregnancy in adrenalectomized rats. Holtzman's strain albino rats were adrenalectomized on day 8 of pregnancy and at the same time were laparotomized to observe the number of implantations. Adrenalectomy on day 8 caused abortions or fetal resorption in almost all rats. Administration of 5 or 50 IU HCG in adrenalectomized rats, from day 8 through 14 or 19, was not able to maintain gestation, resulting in fetal resorption with many placentomas and placental scars. However, a single injection of 5 IU or 1 IU HCG administered on day 8 only maintained the pregnancy to full term in adrenalectomized rats. Hence, the present experiment indicates that replacement therapy of a single dose of 5 IU or 1 IU HCG might be sufficient for maintaining pregnancy in adrenalectomized rats.     

Teratogenic effects of carboplatin, an oncostatic drug, administered during the early organogenetic period in rats

In the preceding study, no teratological effects against rat fetuses were observed when carboplatin, an oncostatic platinum coordination complex, was dosed to their dams from days 7 to 17 of gestation at a dose level of 4 mg/kg/day. However, there are a few reports which show the teratogenic action of carboplatin injected from days 6 to 15 of pregnancy at a dose level of 6 mg/kg/day. In the present study, carboplatin was administered intravenously to pregnant female Crj: CD (Sprague-Dawley) rats from days 6 to 9 or 7 to 10 of gestation at a dose level of 6 mg/kg/day in order to know the teratogenicity of this drug. Carboplatin were highly embryolethal in dams when dosed from days 6 to 9 of gestation, but not in animals when injected from days 7 to 10 of pregnancy. Carboplatin also produced external, internal and skeletal anomalies in fetuses such as gastroschisis, dilatation of cerebral ventricles, cleft sternum, fused ribs, malformed thoracic vertebra when administered from days 6 to 9 of gestation, but not in conceptuses when dosed from days 7 to 10 of pregnancy. However, the delayed ossification which was ascribed to the fetal growth retardation was observed in rats treated with this drug during both administration periods. These results suggest that carboplatin is embryotoxic, inducing intrauterine death and congenital malformations in rats, when injected during the early stages of gestation including day 6 of pregnancy.     

Evaluation of the embryolethality of butyl benzyl phthalate by conventional and pair-feeding studies in rats

The embryolethality of butyl benzyl phthalate (BBP) was studied in Wistar rats. Pregnant rats were given BBP at dosages of 0 (control) and 2.0% in the diet from day 0 to day 20 of pregnancy. Daily intake of BBP was 974 mg kg-1 for the 2.0% BBP group. In this group, all dams exhibited complete resorption of all the implanted embryos, and their food consumption, body weight gain and adjusted weight gain (body weight gain excluding the gravid uterus) during pregnancy were markedly lowered. To determine whether the embryolethality was the result of reduced food-consumption during pregnancy, a pair-feeding study was performed in which the pregnant rats received the same amount of diet consumed by the 2.0% BBP-treated pregnant rats. The pair-fed and 2.0% BBP-treated pregnant rats showed significant and comparable reductions in the adjusted weight gain. In the pair-fed group, the incidences of postimplantation and total losses were higher than those in the control group, and the number of live fetuses per litter was lower than the control value. However, the complete resorption of all the implanted embryos was not found in any of the pair-fed pregnant rats. It could be concluded that the embryolethality observed in the 2.0% BBP-treated pregnant rats is attributable to the effects of dietary BBP but not to the maternal malnutrition from reduced food consumption during pregnancy.     

The interactive effects of alcohol and cocaine on maternal and fetal toxicity in the Long-Evans rat

The number of obstetric patients with polydrug abuse problems has increased substantially in recent years. One of the most common drug combinations is alcohol and cocaine. The effect of this drug combination on pregnancy is, therefore, of interest. Consequently, the present study investigated the relative and interactive effects of these two drugs on pregnancy outcome in an animal model. Alcohol and cocaine were administered, both separately and in combination, to separate groups of pregnant Long-Evans rats from gestation day 7-19. Animals were then sacrificed and examined on gestation day 20. Control animals were given vehicle only or were nontreated. The isobolographic method was used to evaluate the effects of the alcohol-by-cocaine interaction on select maternal and fetal variables. This method of analysis indicated that alcohol and cocaine had interactive effects that were linearly additive for some variables and infraadditive for others. In general, the results suggest that the alcohol-plus-cocaine drug combination poses a greater risk to pregnancy than either drug alone.     

Oral dosage study of miporamicin administered during the period of fetal organogenesis in rats

Experiments were conducted to assess the effects of miporamicin (MPM) on prenatal and postnatal development of fetuses and offsprings of rats receiving the compound at oral dosages of 40, 200, or 1,000 mg/kg/day during the organogenesis stage of gestation. The drug treatment had no appreciable effect on maternal body weight during pregnancy or lactation period. The rats showed decreased food intake and increased water intake during gestation period in the groups given greater than or equal to 200 mg/kg/day, and increased food and water intakes during lactation period in the group given 1,000 mg/kg/day. There was no macroscopic evidence of changes indicative of any effect of the treatment in the viscera of rat dams at terminal necropsy. Observation of the fetuses did not reveal any effect of the treatment with MPM with respect to the number of implantations, the number of living fetuses, the death rate of fetuses or incidence of external, visceral, or skeletal anomalies. Male fetal weights were low in the groups given greater than or equal to 200 mg/kg/day. Observation of the offspring post partum failed to disclose any abnormalities indicative of adverse effects of the treatment with respect to birth index, viability index, weaning index, postnatal external differentiation, body weight changes, external morphology, skeleton, viscera, organ weight, functional and behavioral tests, emotion, learning ability, or reproductive performance, or in respect of prenatal development of their fetuses (F2). It is concluded from the results that no effect dose levels of MPM was 40 mg/kg/day in rat dams, 40 mg/kg/day also for their fetuses, and 1,000 mg/kg/day for postnatal development of the offspring under the experimental conditions described.     

The Pregastrulation Rat Embryo: A Possible Object for Studies of Retinoid-Associated Teratogenicity

The study examined whether pregastrulation rat embryos can be used as a model for demonstrating in vivo the toxic and teratogenic effects of all-trans retinoic acid (tRA). The tRA was administered per os to Wistar rats on day 6 of gestation (the presence of sperm was taken as day 1) in a single dose of 120 mg/kg body weight. In the litters examined on days 9 and 14 of gestation, tRA significantly increased the number of resorbed embryos. Examination on day 14 of pregnancy revealed that tRA also caused a high proportion of embryos to be growth-retarded (with CR length at least 20% less than that of controls). Growth retardation was found in 6 of 7 tested litters. Both external and skeletal malformations were observed in 20 day fetuses when tRA was administered on day 6 of gestation. Rats receiving tRA on days 11 or 14 of gestation served as positive controls, and also showed malformations. These results indicate that pregastrulation rat embryo can be used for assessing the pathways contributing to the teratogenic effect of tRA.     

Maternal hepatic and embryonic effects of 1,2,3,4-tetrachlorobenzene in the rat

To assess possible maternal hepatic and reproductive effects of this uncharged, low molecular weight, lipophilic chlorinated benzene 0, 100, 300 and 1000 mg/kg/day of 1,2,3,4-tetrachlorobenzene (TCB) was orally administered to pregnant rats on days 9-13 of gestation and the animals were killed on day 14 of pregnancy. Phenobarbital and beta-naphthoflavone were administered to other pregnant rats as positive hepatic controls. Maternal mortality (7/19 rats) was increased and body weight gain was greatly decreased in the 1000 mg/kg/day TCB group. Liver to body weight ratio and hepatic microsomal protein content were unaffected by any TCB treatment. On day 14 maternal NADPH-cytochrome c reductase activity was increased at 1000 mg/kg/day, while the maternal hepatic microsomal cytochrome P-450 content was significantly induced by both 300 and 1000 mg/kg/day of TCB. Microsomal N-demethylation of aminopyrine was increased from 2.6 to 4.0 and 4.5 nmol/mg protein/min at doses of 300 and 1000 mg/kg TCB, respectively. However, maternal hepatic microsomal ethoxyresorufin O-deethylase activity was not consistently increased by TCB. Hepatic glutathione S-transferase activity towards 1,2-dichloro-4-nitrobenzene was increased only by the 1000 mg/kg/day TCB treatment. The rate of microsomal p-nitrophenol and phenolphthalein glucuronidation was increased by TCB administration. Embryonic growth was adversely affected by TCB treatment. Yolk sac diameter, embryonic crown-rump length, and head length were all decreased by treatment with 300 mg/kg/day TCB. This TCB treatment did not significantly elevate the number of dead or abnormal embryos.     

Strain comparisons of atrazine-induced pregnancy loss in the rat

Atrazine was administered by gavage, in 1% methylcellulose, to F344 Sprague-Dawley (SD), and Long Evans (LE) rats at 0, 25, 50, 100, or 200 mg/kg/day on gestation days 6 through 10. The dams were allowed to deliver and litters were examined postnatally. The F344 strain was the most sensitive to atrazine's effects on pregnancy, showing full-litter resorption (FLR) at >/=50 mg/kg. In surviving F344 litters, prenatal loss was increased at 200 mg/kg. In SD and LE rats, FLR occurred only at 200 mg/kg. Delayed parturition was seen at >/=100 mg/kg in F344 and SD rats. Regarding maternal toxicity, the SD dams were the most sensitive, with weight loss at >/=25 mg/kg. When 200 mg/kg was administered to F344 rats on days 11 through 15 (after the LH-dependent period of pregnancy), no FLR was seen. These findings suggest that atrazine-induced FLR is maternally mediated, and consistent with loss of LH support of the corpora lutea.     

Fetal development in alloxan-treated rats

The effect of alloxan on embryo and fetal development in rats was evaluated. Alloxan was injected intraperitoneally (ip) in pregnant rats at doses of 80 to 150 mg/kg at Day 0 (day of fertilization), and 110 mg/kg at Day 4 of pregnancy. Hyperglycemia was rarely produced at alloxan doses from 80 to 100 mg/kg, and the frequency of malformations observed was low. Higher doses (110 to 150 mg/kg) caused severe hyperglycemia, and maternal or embryonic death. When 110 mg/kg was administered on Day 4 of gestation (the day before embryo implantation), all rats had resorption nodules and litters with embryos with delayed growth. We recommend the induction of diabetes mellitus on Day 4 of pregnancy for studies of diabetes–gestation interaction.     

Continuous Deep Intravenous Infusion in Rat Embryotoxicity Studies: The Effects of Infusion Volume and two Different Infusion Fluids on Pregnancy

Intravenous infusion over long periods is an increasingly common method of administration for novel medicinal agents. This investigation was undertaken to evaluate the suitability of a new catheter implantation technique in the rat and to determine the effects of two different infusion fluids and volumes on litter parameters. Female Sprague-Dawley rats were anesthetized on day 1 of gestation and an indwelling catheter was implanted into the posterior vena cava by introduction into the femoral vein. A swivel joint in the roof of the cage allowed unrestricted movement of the animal. One group of rats was not treated further. Other groups were maintained on continuous infusion with physiological saline or isotonic glucose (dextrose) solution at various rates until day 15 of gestation (the test article would normally be dissolved in the infusion fluid starting from day 6 of gestation). Anesthesia and catheter implantation without infusion caused a slight transient reduction in maternal weight gain by comparison with historical data from untreated rats. This parameter then showed a clear inverse relationship to infusion volume in the infused groups. An infusion rate of 0.25 mL/h (i.e., 24 mL/kg day^?1) did not adversely affect gestation. Infusion of 1.0 mL/h of saline caused an increase in early resorption incidence and retarded fetal development. The same volume of isotonic glucose solution caused only a minor increase in resorptions with no effects on surviving fetuses.     

Respiration in sprague-dawley rats during pregnancy

Minute ventilation and tidal volume increase in humans during pregnancy. Little data exists, however, on the respiration in pregnant rats, despite their widespread use as an animal model. Since respiration will affect the pharmacokinetics of volatile compounds and ultimately the dose to the fetus, we conducted a study to evaluate respiration in rats during pregnancy. Whole-body plethysmography was used to measure the breathing frequency and tidal volume approximately every other day from gestation day (GD) 1 to 21 in 16 timed pregnant and 16 nonpregnant, female, Sprague-Dawley rats. Minute ventilation was calculated as a product of the breathing frequency and tidal volume, and the body weight of each rat was used to determine the scaled ventilation. Multivariate analysis of variance methods for a repeated-measures design were used to analyze the respiratory data. Breathing frequency was not affected by pregnancy; however, tidal volume was somewhat greater in pregnant versus nonpregnant rats. The increase in tidal volume resulted in significantly increased minute ventilation in pregnant rats compared to nonpregnant rats during the latter period of gestation. Due to the increased body weight of the pregnant rats, the scaled ventilation at the end of gestation was significantly lower in pregnant rats compared to nonpregnant rats. This study provides important reference values that can be used in pharmacokinetic models during pregnancy.     

Teratogenesis study of o-toluenediamine in rats and rabbits

o-Toluenediamine in corn oil was administered po to Sprague-Dawley rats at dosages of 10, 30, 100, or 300 mg/kg body wt/day during Days 6 through 15 of gestation. All animals were killed on Day 20 of gestation. A similar study was conducted with Dutch-Belted rabbits dosed po daily at 3, 10, 30, or 100 mg of o-toluenediamine/kg body wt/day from Days 6 through 18 of gestation. Rabbits were killed on Day 29 of gestation. Maternal toxicity was indicated at 300 mg/kg in rats and 100 mg/kg in rabbits by reduced body weight gain during gestation. Fetal body weight was reduced at the highest dosage in both rats and rabbits. In addition, at the high dosage, an increase in the number of resorption sites in rabbits were noted. Skeletal examination of rats showed increased incidence of missing sternebrae at 300 mg/kg and incompletely ossified vertebrae at 100 and 300 mg/kg in comparison to control fetuses. The effects on the fetus could be the result of maternal toxicity. There was no evidence of teratogenic effects or effects on the dams at dosages through 30 mg/kg body wt.