Teratogenicity and Embryotoxicity of Orally Administered Fenchlorphos in Blue Foxes

Pregnant blue foxes (Alopex lagopus) were administered fenchlorphos (0-0-dimethyl-0-(2,4,5-trichlorophenyl) phos-phorothioate) orally at a dose of 100 mg/kg/day in different periods of gestation. The dose chosen represents the therapeutic dose for the treatment of parasitic lesions. At term the mean number of whelps were recorded, and they were killed and examined for external, visceral and skeletal malformations. Of 19 medicated vixens the mean number of live whelps at term was 1.2 per vixen versus 9.5 in the control group. There was an evident predominance of males in the medicated groups. Several malformations of the head were registered, among them incomplete ossification of the skull bones, cleft palate, hydrocephalus internus and externus. Minor malformations like extra ribs or missing ribs occurred in the medicated groups. Congenital alopecia, hypoplastic kidneys, and hydronephrosis were observed in all the whelps in 1 medicated group. No significant difference in total brain weight, cerebellum weight or the cerebellum-to-total-brain weight was observed. Histological examination of the cerebellum showed a narrowing or absence of the granular and the molecular layers of the cortical zone.     

Sensitive periods for developmental toxicity of orally administered artesunate in the rat

BACKGROUND: Artesunate has been reported to cause embryolethality and malformations when administered orally to rats during organogenesis. The purpose of this study was to determine the most sensitive period(s) for the induction of these effects in order to provide clues about possible mechanisms and to identify a short treatment regimen for further studies. METHODS: Pregnant rats were orally administered artesunate (10, 17 or 30 mg/kg/day) on single or multiple days of gestation. Cesarean sections and fetal evaluations were conducted on Day 21 postcoitum (pc). RESULTS: Embryolethality, cardiovascular malformations and a syndrome of skeletal defects were observed after single doses on days 10 to 14 pc, while no developmental effects were observed before (day 9 pc) or after (days 16 or 17 pc) that period. The most sensitive day for embryo lethality was day 11 pc, where lethality occurred with a very steep dose response (postimplantation loss was ～15% at 10 mg/kg and 100% at 17 mg/kg/day). The most sensitive day for the induction of malformations was day 10 pc. Malformations tended to occur in partially resorbed litters and included cardiovascular defects and bent and misshapen long bones and scapulae. CONCLUSIONS: The sensitive window for developmental toxicity of artesunate in the rat was identified as days 10 to 14 pc. Single oral doses produced embryolethality and similar cardiovascular and skeletal malformations as previously reported in longer term dosing experiments. These single dose treatment regimens could be useful to further investigate the mechanistic basis for artesunate‐induced developmental toxicity. Birth Defects Research (Part B) 2008. © 2008 Wiley‐Liss, Inc.     

Developmental toxic effects of antifungal flusilazole administered by gavage to mice

BACKGROUND: The developmental toxicity of flusilazole was studied in CD-1 mice after oral administration. METHODS: Pregnant mice were given flusilazole at doses of 0 (corn oil), 10, 20, and 40 mg/kg/day, by gavage, on gestational days (GD) 6-15. RESULTS: Maternal toxicity, as evidenced by reduction in body weight gain and signs of toxicity, was observed at the middle- and high-dose groups. No significant incidence of resorptions or death was observed in any of dose groups. There was a pronounced reduction in fetal weight, which was significantly lower than control from 20 and 40 mg/kg/day. There was no significant increase in the incidence of fetuses with external or visceral malformations in any of dose groups, but there was a significant increase in the incidence of skeletal malformations was observed at 20 and 40 mg/kg/day. CONCLUSIONS: The results of this study reported marked maternal toxicity, growth retardation, and skeletal abnormalities in the mid- and high-dose groups. It seems likely that marked maternal toxicity contributed to the observed alterations in fetal growth retardation and skeletal development. The no-observed-effect level in the present study for maternal and developmental toxicity was 10 mg/kg/day.     

Malformations in rat fetuses induced by trypan blue

Malformations of fetuses obtained from Wistar rat dams treated with trypan blue during gestation were studied. Fetuses were examined on day 20 of gestation. One hundred and twenty-seven fetuses showed abnormalities of the external features, skeleton and internal organs, separately or in combination. External malformations were found in 108 fetuses. The most frequent external malformation was anomaly of tail. Spina bifida, club foot, exencephaly and anal atresia were also observed frequently. Skeletal malformations were detected in 48 fetuses. Deformity of vertebrae in the lumbar, sacral and/or caudal regions was found in 46 fetuses. Internal malformations were observed in 27 fetuses. Anomaly of heart and/or great vessels, hydrocephaly and micro- or anophthalmia were observed frequently. About 90% of the fetuses with skeletal malformations also showed some external malformations. In contrast, about 48% of the fetuses with internal malformations also had some external malformations. These results suggest that, for teratological study, internal examination is more important in detecting malformations of fetuses than skeletal examination.     

Developmental stages of the CD (Sprague-Dawley) rat skeleton after maternal exposure to ethylene glycol.

Ethylene glycol (EG), a chemical which causes skeletal malformations in rats, was administered by gavage to sperm positive CD rats on gestational days (gd) 6 through 15 at doses of 0 or 2,500 mg/kg/day to assess its effects on the pre- and postnatal skeletal development. Dams and fetuses/pups were killed on gd 18, 20, postnatal day (pnd) 1, 4, 14, 21, or 63, and offspring were double-stained for examination of skeletal malformations and degree of ossification of rapidly developing skeletal districts. No difference in gestational day of delivery between controls and the EG-treated dams was seen. Fetal weights per litter were significantly decreased with EG treatment in both the gd 18 and 20 groups. Pup body weight on pnd 1 was significantly below controls; however, EG had no effect on pup body weight on pnd 4-63. The percentage of fetuses/pups with skeletal malformations per litter was significantly increased after EG exposure for all time points except at pnd 63, with a predominance of axial skeletal defects. The percentages of total ossification, of sternabrae ossified, and of vertebral centra ossified were significantly reduced in the EG groups on gd 20 and on pnd 1-21, but not on gd 18 or on pnd 63. When the ossification data were subjected to statistical analysis with fetal/pup weights as a covariate, the values for EG-exposed pups on gd 20 were not statistically significantly different from the control values. The reduced ossification values for EG-exposed pups on pnd 1-21 retained statistical significance even after covariate analysis. There was no effect of dose or body weight on ossification of fore- or hindlimb digits. In conclusion, the differences in incidence of skeletal alterations observed prenatally and through pnd 21 were not evident by pnd 63, suggesting that perinatal skeletal abnormalities may not always be permanent.     

Teratogenicity of zinc deficiency in the rat: study of the fetal skeleton

Zinc deficiency (ZD) is teratogenic in rats, and fetal skeletal defects are prominent. This study identifies fetal skeletal malformations that affect calcified and non-calcified bone tissue as a result of gestational zinc deficiency in rats, and it assesses the effect of maternal ZD in fetal bone calcification. Pregnant Sprague-Dawley rats (180-250 g) were fed 1) a control diet (76.4 micrograms Zn/g diet) ad libitum (group C), 2) a zinc-deficient diet (0 microgram/g) ad libitum (group ZD), or 3) the control diet pair-fed to the ZD rats (group PF). On day 21 of gestation, laparotomies were performed. Fetuses were weighed, examined for external malformations, and stained in toto with a double-staining technique for the study of skeletal malformations. Maternal and fetal tissues were used for Zn, Mg, Ca, and P determinations. Gross external malformations were present in 97% of the ZD fetuses. No external malformations were found in fetuses from groups C and PF. Ninety-one percent of cleared ZD fetuses had multiple skeletal malformations, whereas only 3% of the fetuses of group PF had skeletal defects; no skeletal malformations were found in fetuses from group C. Some of the skeletal malformations described in the ZD fetuses, mainly affecting non-calcified bone, were not mentioned in previous reports, thus stressing the importance of using double-staining techniques. Examination of stained fetuses and counting of ossification centers revealed important calcification defects in ZD fetuses. These effects were confirmed by lower Ca and P concentrations in fetal bone with alteration of the Ca:P ratio.     

Developmental toxicity of artesunate and an artesunate combination in the rat and rabbit

The artemisinins are playing an increasingly important role in treating multidrug-resistant malaria. The artemisinin, artesunate, is currently in use in Southeast Asia and is advocated for use in Africa. In these areas, more than one million people die of malaria each year, with the highest mortality occurring in children and pregnant women. To test the developmental toxicity in ICH-compliant animal studies, embryofetal development studies were conducted in rats and rabbits treated with artesunate alone or a three-drug combination (CDA) consisting of chlorproguanil hydrochloride, Dapsone, and artesunate in the ratio 1.00:1.25:2.00. Developmental toxicity seen with CDA could be attributed to the administered dose of artesunate. The hallmark effect of artesunate exposure was a dramatic induction of embryo loss, apparent as abortions in rabbits and resorptions in both rats and rabbits. In addition, low incidences of cardiovascular malformations and a syndrome of skeletal defects were induced at or close to embryolethal doses of artesunate in both rats and rabbits. The cardiovascular malformations consisted of ventricular septal and vessel defects. The skeletal syndrome consisted of shortened and/or bent long bones and scapulae, misshapen ribs, cleft sternebrae, and incompletely ossified pelvic bones. These developmental effects were observed largely in the absence of any apparent maternal toxicity. The no or low adverse effect levels were in the range of 5 to 7 mg/kg/day artesunate. Encouragingly, no adverse drug-related developmental effects have been observed in a limited number of pregnant women (more than 100 first trimester and 600 second and third trimester) treated with artemisinins, primarily artesunate. Investigations of the mechanism of developmental toxicity are ongoing to attempt to determine whether rats and rabbits are more sensitive to artemisinins than humans.     

Comparison of the developmental toxicity of aspirin in rabbits when administered throughout organogenesis or during sensitive windows of development

BACKGROUND: A review of the nonsteroidal anti‐inflammatory drug (NSAID) literature suggested occurrences of low‐level incidences of cardiovascular and midline defects in rabbit fetuses exposed in utero. Aspirin (acetylsalicylic acid, ASA) is a widely used NSAID that irreversibly inhibits cyclooxygenases (COXs) 1 and 2. ASA has been studied extensively in rats and has consistently increased low‐incidence cardiovascular malformations and defects in midline closure. The objectives of the current study were to comprehensively define the developmental toxicology profile of ASA in rabbits by using a dosing paradigm encompassing the period of organogenesis and to test the hypothesis that maternal gastrointestinal toxicity after repeated dose administrations hampers the detection of low‐incidence malformations with ASA in rabbits by limiting ASA administration to sensitive windows for cardiovascular development and midline closure. METHODS: ASA was administered to pregnant New Zealand White rabbits from gestation days (GDs) 7 to 19 at dose levels of 125, 250, and 350 mg/kg per day and as single doses of 500, 750, or 1000 mg/kg on GD 9, 10, or 11. Cesarean sections were performed on GD 29, and the fetuses were examined for external, visceral, and skeletal development. RESULTS: In the repeated dose study, maternal toxicity was exhibited in the 250‐ and 350‐mg/kg per day groups by mortality and decreased food consumption and body weight gain. In the single dose studies, maternal toxicity was exhibited at all doses by reductions in body weight gain and food consumption for 3 days after treatment. Fetal body weight was significantly reduced in the repeated dose study at 350 mg/kg per day. Fetal weights were not affected by single doses of ASA on GD 9, 10, or 11. There were no treatment‐related external, visceral, or skeletal malformations associated with ASA administration throughout organogenesis or with single doses administered during critical developmental windows. CONCLUSION: These findings supported previous work demonstrating that ASA is not teratogenic in rabbits, as opposed to rats, even when large doses are administered on single days during specific windows of development. Birth Defects Research (Part B) 68:38–46, 2003. © 2003 Wiley‐Liss, Inc.     

Axial skeletal malformations induced by acetazolamide in rabbits.

In order to evaluate the teratogenic potential of acetazolamide in rabbits, three groups of 18 artificially inseminated females were treated orally with 50, 100, or 150 mg/kg/day of acetazolamide on days 6-18 of gestation. These doses induced maternal acidosis and electrolyte changes, consistent with those reported in rats and considered to be a result of carbonic anhydrase inhibition, as well as reductions in maternal body weight gain. At cesarean sections, average fetal body weights in the acetazolamide groups were dose-dependently decreased compared with controls. There were no effects of acetazolamide on embryonic survival or external morphology of live fetuses. In the fetal skeletal examination, thoracic and lumbar vertebral malformations occurred in 0.7%, 3.9%, and 6.1% of fetuses in the 50, 100, and 150 mg/kg/day groups, respectively, compared with none in the control group. In addition, missing vertebra was seen in a small number of fetuses in the 100 and 150 mg/kg/day groups. These axial skeletal malformations were, in some cases, associated with costal malformations. These results indicate that acetazolamide at maternotoxic doses can produce axial skeletal malformations in the rabbit.     

Developmental toxicity evaluation of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in Wistar rats

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is a genotoxic chlorination by-product in drinking water. There is some evidence that it has developmental toxic effects in vitro but its potential to cause developmental effects in vivo is not known. The developmental effects were evaluated in Wistar rats. Rats (22-26 dams per dose group) were administered MX by gavage at the dose levels of 3, 30, or 60 mg/kg in water on gestation days 6-19. Control animals received plain water. Clinical signs, body weight, and food and water consumption were recorded for the dams. On gestation day 20, a cesarean section was performed and the ovaries anduterine contents of the dams were examined and the liver, kidneys, spleen, and thyroid glands weighed. The fetuses of all dose groups were weighed, sexed, and observed for external and skeletal malformations and the fetuses of the two highest dose groups were evaluated for visceral malformations. The highest dose, 60 mg/kg of MX, was slightly toxic to the dams. It decreased the corrected body weight gain of dams by 32% and the water consumption by 16-17%. Kidney and liver weights were slightly increased. MX did not affect the number of implantations nor did it cause any resorptions. The body weights of fetuses were not significantly affected. MX did not cause external malformations or skeletal anomalies. Two fetuses at 60 mg/kg and one fetus at 30 mg/kg had major visceral malformations (persistent truncus arteriosus, diaphragmatic hernia, dilated aorta with a stenosis of pulmonary arteries) and two minor artery abnormalities were observed in those animals. The frequency of unilateral displaced testis was slightly higher (9.2%) in the 60-mg/kg dose group than in controls (1.6%). Since the abnormalities did not form a consistent pattern and occurred most at maternally toxic dose, we conclude that MX can be regarded as non-teratogenic.     

Teratogenic effects of nickel chloride on embryonic mice and its transfer to embryonic mice.

Administration of nickel chloride to the pregnant mice on the seventh to eleventh day of their gestational period, resulted in significant embryotoxic effects in terms of an increased resorption rate, a decreased fetal weight, delay in skeletal ossification and high incidence of malformation. Among the cases of fetal malformation, the following malformations were observed to occur at a higher rate of incidence: acephalia, exencephaly, cerebral hernia, open eyelid, cleft palate, micromelia, ankylosis of the extremity, club foot and skeletal anomalies. Most skeletal anomalies were in the form of vertebral and/or rib fusions and were found mostly at thoracic and lumbar levels. The concentration of nickel retained in embryonic tissues was 800 times higher in the exposed compared to control groups and indicated that increased tissue levels of nickel chloride had a toxic influence on the developing embryo.     

Effects of low-frequency magnetic fields on fetal development in rats

We studied effects of alternating magnetic fields on the embryonic and fetal development of rats. Mated females of the Han:Wistar-strain were sham exposed or exposed continuously to a 50-Hz field or to a 20,000 pulse-per-second (pps) sawtooth magnetic field from day 0 to day 20 of pregnancy for 24 h/day until necropsied on day 20. The respective peak-to-peak intensities of the fields were 35.6 μT (sinewave) and 15.0 μT (sawtooth). Each treatment group contained 72 bred females. Control animals were kept under the same conditions without the magnetic field. No adverse effects were seen in the dams. The mean numbers of implantations and living fetuses per litter were statistically significantly increased in the 50-Hz group. There were, however, three total resorptions of litters in dams of the control group, which contributed to the difference in the number of living fetuses. The corrected body-mass gains (gains without uterine content) of dams were similar in all groups. Pregnancy rates, incidences of resorptions. late fetal deaths, and fetal body masses were similar in all groups. The incidence of fetuses with minor skeletal anomalies was statistically significantly increased in both exposed groups. Only one serious malformation (anophthalmia, sawtooth-exposed group) and a few minor visceral malformations were found. In conclusion, the magnetic fields used in this study did not increase the incidence of major malformations or resorptions in Wistar rats. The increased number of skeletal anomalies and implantations we observed indicates, however, that some developmental effects in rats may attend exposure to time-varying magnetic fields. © 1993 Wiley-Liss. Inc.     

Requirement for Pbx1 in skeletal patterning and programming chondrocyte proliferation and differentiation

Pbx1 and a subset of homeodomain proteins collaboratively bind DNA as higher-order molecular complexes with unknown consequences for mammalian development. Pbx1 contributions were investigated through characterization of Pbx1-deficient mice. Pbx1 mutants died at embryonic day 15/16 with severe hypoplasia or aplasia of multiple organs and widespread patterning defects of the axial and appendicular skeleton. An obligatory role for Pbx1 in limb axis patterning was apparent from malformations of proximal skeletal elements, but distal structures were unaffected. In addition to multiple rib and vertebral malformations, neural crest cell-derived skeletal structures of the second branchial arch were morphologically transformed into elements reminiscent of first arch-derived cartilages. Although the skeletal malformations did not phenocopy single or compound Hox gene defects, they were restricted to domains specified by Hox proteins bearing Pbx dimerization motifs and unaccompanied by alterations in Hox gene expression. In affected domains of limbs and ribs, chondrocyte proliferation was markedly diminished and there was a notable increase of hypertrophic chondrocytes, accompanied by premature ossification of bone. The pattern of expression of genes known to regulate chondrocyte differentiation was not perturbed in Pbx1-deficient cartilage at early days of embryonic skeletogenesis, however precocious expression of Col1a1, a marker of bone formation, was found. These studies demonstrate a role for Pbx1 in multiple developmental programs and reveal a novel function in co-ordinating the extent and/or timing of proliferation with terminal differentiation. This impacts on the rate of endochondral ossification and bone formation and suggests a mechanistic basis for most of the observed skeletal malformations.     

Stage-specific skeletal and visceral defects of the I(Kr)-blocker almokalant: further evidence for teratogenicity via a hypoxia-related mechanism.

BACKGROUND: As a class effect, potent I(Kr)-blockers have been shown to induce stage-specific external malformations. The aim of this study was to investigate whether I(Kr)-blockers also induce stage-specific visceral and skeletal defects and to further elucidate a proposed arrhythmia-hypoxia hypothesis. METHODS: Single oral doses of the selective I(Kr)-blocker almokalant (ALM) 25-150 micromol/kg, 7-14 dams/group, were given to Sprague-Dawley rats on gestation days (GD) 10-14, and the fetuses were examined for malformations on GD 21. One group was pretreated with the spin-trapping agent, alpha-phenyl-N-t-butylnitrone (PBN), given intraperitoneally 1 hr before ALM on GD 11. RESULTS: Cardiac ventricular septum defects and vascular malformations were observed after dosing on GD 10-11 and, to a lesser degree, on GD 12-13. Urogenital defects, absence/malposition of the postcaval lung lobe, and attenuated diaphragm were observed mainly on GD 10-11. Skeletal examination showed a high incidence of vertebral abnormalities on thoracic level on GD 10, on lower thoracic to caudal level on GD 11, and sternebral defects were observed all days. On GD 13 brachy-, oligo-, and syndactyly of the forepaw were induced, and of the hindpaw on GD 14. PBN reduced the incidence of both visceral and skeletal defects. CONCLUSIONS: The stage specificity of observed visceral and skeletal defects correlates well with what has been reported in the literature after temporary interruption of oxygen supply during the same stages of development. The protective effect by PBN present further evidence that the teratogenicity of potent I(Kr)-blockers is related to induction of hypoxia- reoxygenation injury due to embryonic cardiac arrhythmia.     

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.     

Reduction of all-trans-retinoic acid-induced teratogenesis in the rat by glycine administration

BACKGROUND: Prenatal rat embryo exposure to retinoids induces severe malformations in various organs; the most active and teratogenic metabolite is all-trans-retinoic acid (atRA). The mechanisms of this embryopathy are only partly known. In the present study, the influence of glycine on the teratogenicity of atRA was investigated. METHODS: Embryos from 5 groups of white rats were studied: Group 1 remained untreated; Group 2 received glycine 2% in drinking water ad libitum from the first gestational day (GD 1); Group 3 was administered vehicle (corn oil); Group 4 was treated with atRA (50 mg/kg of body weight) injected (IP); and Group 5 was treated with atRA (50 mg/kg of body weight IP) plus glycine 2% in drinking water ad libitum from GD 1. atRA was administrated daily from GD 8-10. Dams were killed on the 21st day of pregnancy, and their fetuses were examined to detect external, visceral, and skeletal malformations. RESULTS: The results show that the atRA-administered dose is not toxic for the dams, and that although fetal death was not observed, it produced abnormalities in the fetuses. Glycine reduced atRA-induced teratogenic effects (external and skeletal defects). CONCLUSIONS: The results indicate that glycine effectively reduces the teratogenic effects of atRA. Thus, glycine might be useful for the prevention of vitamin A teratogenicity.     

Teratology of intravaginally administered contraceptive jelly containing octoxynol-9 in rats

Octoxynol-9, a nonionic surfactant used as a spermicidal agent in ORTHO-GYNOL (registered trademark) Contraceptive Jelly (Ortho Pharmaceutical Corporation, Raritan, NJ), was administered intravaginally to pregnant Sprague Dawley COBS CD rats at dosages of 0.5 mg/kg/day and 5 mg/kg/day (two-thirds and six times the clinical dosage) on days 6-15 of gestation in order to assess its teratogenic potential. Untreated, sham, and vehicle control groups were also incorporated into the study protocol. No meaningful differences were observed between the treated and control groups in maternal toxicity, maternal reproductive parameters, fetal toxicity, and the incidence of external, visceral, and skeletal malformations or developmental variations. It is concluded that octoxynol-9 is not embryotoxic or teratogenic when administered intravaginally to rats during organogenesis.     

Importance of genetic predisposition and maternal environment for the occurrence of congenital malformations in offspring of diabetic rats

Previous experimental studies have implicated a genetic component in the induction of malformations in the offspring of diabetic rats. We have compared the outcome of diabetic pregnancy in two outbred (sub)strains of Sprague-Dawley rats (with low incidence [H] and high incidence [U] of skeletal malformations in the offspring) and hybrids between them. The fetuses of diabetic H mothers had no skeletal malformations and the lowest frequency of resorptions (8-9%), regardless of embryo type (H/H or H/U). When the diabetic mother was U or from the hybrid strain (H/U) and the offspring were of the mixed H/U type, we found increased resorption (16-21%) and skeletal malformation (3-5%) rates. If instead the embryos contained a major U genome [either U/U or U/(H/U)], further increased resorptions (23-30%) and skeletal malformations (17-19%) resulted. The H/H and U/U embryonic susceptibility to defined teratogens (3-6 mg/ml D-glucose, 4-8 mM B-hydroxy-butyrate) were compared in whole embryo culture and found to be similar, suggesting that the malformations occurring in vivo may have a different etiology than those found in vitro. In the rat model studied, diabetes in the mother appears to cause a disturbance of early stages of embryogenesis in genetically predisposed embryos. This early disturbance results in skeletal malformations and seems to require inducing factor(s) in addition to increased levels of D-glucose and B-hydroxybutyrate. The findings are in concert with the notion of a mixed genetic-environmental etiology of malformations in (diabetic) pregnancy.     

Teratogenic effects of trichloroacetonitrile in the Long-Evans rat

Trichloroacetonitrile (TCAN) is among a number of contaminants found in drinking water produced by reactions of chlorine with background organic material. Long-Evans rats were intubated with TCAN (0, 1, 7.5, 15, 35, 55 mg/kg) in a tricaprylin vehicle on gestation days 6-18. The highest dose tested (55 mg/kg) was lethal in 21% of the dams and produced 100% resorptions in two-thirds of the survivors. Only one maternal death was seen at the next-lower dose; however, fetal weight and viability were decreased in a dose-related manner. The percentage of embryolethality was 13.9% at the lowest dose and 78.4% at the high dose, with resorption of entire litters seen at 7.5 mg/kg and above. At all doses, cardiovascular (interventricular septal defect, levocardia, common carotid, and right-sided aortic arch and ductus arteriosus) and urogenital (hypoplastic, missing, misplaced and fused kidneys, and hypoplastic uterine horns) malformations were seen in the offspring. Frequency of these malformations was dose related, ranging from 8% to 35% at the 1.0- and 35-mg/kg doses, respectively. The incidence of total soft tissue malformations was statistically significant at 15 and 35 mg/kg. There were no significant treatment-related changes in the incidence of skeletal malformations. The no-effect dose was established by statistical analysis to be 1.0 mg/kg/day.