Developmental toxicity evaluation of trimethylolpropane caprylate caprate in Sprague-Dawley rats

The developmental toxicity potential of trimethylolpropane caprylate caproate (TMPCC, CAS no. 11138-60-6) was evaluated in rats. Sprague-Dawley rats were administered TMPCC in a corn oil suspension dermally at dose levels of 0, 200, 600, or 2,000 mg/kg/day on gestation days (GD) 6-15 (sperm positive day=GD 0). Caesarean sections were performed on GD 20 and fetuses were evaluated for viability, growth, and external, visceral, and skeletal abnormalities. Each group consisted of 25 females, with at least 22 per group being pregnant. The two highest dose levels caused some local irritation at the site of application, but no decreases in maternal weight gain. There were no differences from control in any of the developmental parameters measured, including embryo/fetal viability, fetal weight, malformations, or variations. TMPCC did not cause any developmental toxicity in the Sprague-Dawley rat at dermal dosages up to 2,000 mg/kg/day.     

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.     

Teratogenic effects of the plant hormone indole-3-acetic acid in mice and rats.

These studies evaluated the teratogenic potential of indole-3-acetic acid (IAA), a naturally occurring plant hormone, in CF-1 mice and Sprague-Dawley rats. Mice were given 5, 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. Rats were given 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. IAA was teratogenic in mice and rats at 500 mg/kg/day; cleft palate was induced in both species at this dose level. In mice, other malformations including exencephaly, ablepharia, dilated cerebral ventricles, and crooked tail were also observed. Mice given 500 mg/kg of IAA gained less than control mice during gestation; no evidence of maternal toxicity was observed in rats. IAA did not cause fetal resorptions in either species and was not teratogenic at dose levels below 500 mg/kg.     

Cocaine as a cause of congenital malformations of vascular origin: experimental evidence in the rat

Cocaine hydrochloride was administered to pregnant Sprague-Dawley rats as a single intraperitoneal dose or as two doses 1-4 hours apart. A single dose administered on day 16 of gestation was teratogenic in a dose-dependent manner, with 40 mg/kg being a no-effect dose and 50 mg/kg the lowest teratogenic dose; 80 mg/kg was lethal to the dam. Forty-eight hours after exposure to a teratogenic dose on day 16 of pregnancy, the fetuses showed severe hemorrhage and edema in the their extremities, particularly the footplates, tail, genital tubercle, and upper lip/nose. When the fetuses were examined on day 21 of gestation, the main externally visible malformations were reduction deformities of the limbs and tail. When two doses of cocaine were administered 1-4 hours apart, the incidence of affected fetuses increased as the time interval between the two doses decreased. Two doses of cocaine administered 2 hours apart were not teratogenic on day 9, 10, 11, 12, 13, or 14 of gestation but did induce reduction deformities on days 15, 16, 17, 18, or 19. The same dose administered 1 hour apart was teratogenic on days 14-19. In general, cocaine administration on gestational days 14, 15, or 16 induced more severe and more widespread hemorrhage and edema than administration on days 17, 18, or 19. In the latter cases, damage was restricted to the distal parts of the hindlimb digits and the tail. The results show that in the rat cocaine is only teratogenic during the late organogenic or postorganogenic period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Conduct and interpretation of a dermal developmental toxicity study with KBR 3023 (a prospective insect repellent) in the Sprague-Dawley rat and Himalayan rabbit

KBR 3023, 1-(1-methyl-propoxycarbonyl)-2-(2-hydroxyethyl)piperidine, a prospective insect repellent being developed by Bayer Corporation, was evaluated for developmental toxicity in the Sprague-Dawley rat and Himalayan rabbit. As the intended human usage of the test compound is topical, the test systems were exposed to the compound via the dermal route. Specifically, the animals were fitted with Elizabethan collars, to reduce the likelihood of oral ingestion, and dermally administered either 0, 50, 200, or 400 mg KBR 3023/kg (rat), and 0, 50, 100, or 200 mg KBR 3023/kg (rabbit) on gestation days 0-19 (rat) and 0-28 (rabbit). Maternal toxicity, as demonstrated by clinical signs and changes in body weight gain and food consumption during gestation, was characterized. Animals were sacrificed on gestation day 20 (rat) and 29 (rabbit), at which time fetuses were removed by cesarean section and a gross maternal necropsy was performed. All fetuses were evaluated for external anomalies. With rats, approximately half of each litter was examined for visceral effects; the other half underwent a skeletal examination. With rabbits, all fetuses underwent both visceral and skeletal examinations. No effects were observed on maternal body weight gain or food consumption in either the rat or rabbit. In the rat, dermal effects (scaling/sloughing), were observed at the dose site of all test substance-treated groups from approximately gestation day 7 until termination of the study. Also noted were an increase in both absolute and relative liver weights in rats in the 400-mg/kg dose group. In the rabbit, dermal effects (slight erythema, squamous and cracked skin) were noted at the dose site of virtually all does administered the test compound, from approximately gestation day 7 until termination. Also observed in the rabbits was a potentially compound-related increase in soft stool, particularly at the highest dose level. In both species, there were no statistically significant effects on any reproductive parameters, or any embryonic endpoints, including pre/post-implantation loss and resorptions. There were no statistically significant effects on litter size or fetal or placental weights. No test compound-related external, visceral, or skeletal findings were observed. No effect on the individual fetal or litter incidence of total malformations or variations was observed and there was no difference in the incidence of malformations between males and females. KBR 3023 Technical, administered as described in these studies, produced maternal effects in the rat (liver weight) at a dose of 400 mg/kg, and in the rabbit (soft stool) in the 200-mg/kg dose group. No developmental toxicity was observed at any dose level.     

Developmental toxicity evaluation of butylparaben in Sprague-Dawley rats

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

Electrocardiographic study of rat fetuses exposed to ethylene glycol monomethyl ether (EGME)

The widely used industrial solvent ethylene glycol monomethyl ether (EGME) is teratogenic to rats and mice, inducing a variety of heart and major vessel abnormalities. In the present study, electrocardiography was used to evaluate heart function in day 20 rat (Sprague-Dawley) fetuses from mothers treated on gestation days 7-13 (sperm = day 1) with 0, 25, or 50 mg/kg EGME by gavage in 10 ml/kg water. The increased incidence of fetuses with cardiovascular malformations (primarily right ductus arteriosus and ventricular septal defect) and abnormal electrocardiograms (EKG) was dose dependent. The most prevalent EKG abnormality was a prolonged QRS wave. Mean QRS intervals were not significantly increased by EGME exposure, but there were significantly more litters in the 50-mg/kg EGME group that had one or more fetuses with QRS complexes of 40 msec or longer. The enhanced duration and the appearance of the aberrant QRS's suggested the presence of an intraventricular conduction delay in these fetuses. Heart rate and other EKG characteristics such as the P wave or P-R and Q-T intervals were not significantly affected by exposure to EGME. There did not appear to be an association between abnormal EKG's and fetal heart dysmorphology.     

Embryotoxic and teratogenic effects of aluminum nitrate in rats upon oral administration

In order to determine the embryotoxic and teratogenic potential of aluminum, pregnant Sprague-Dawley rats were treated by gavage with a daily dose of 180, 360, or 720 mg/kg of aluminum nitrate from the sixth through to the fourteenth day of gestation. Fetal examinations were performed on day 20. The number of corpora lutea, total implants, and resorptions as well as the number of live and dead fetuses in the treated animals were not significantly different from the control group. Therefore, embryolethality of aluminum cannot be induced (as a measure of percent dead and resorbed fetuses). However, exposure of rats to aluminum nitrate resulted in decreased fetal body weight and increased the incidence and types of external, visceral, and skeletal malformations and variations in all the treated groups. Consequently, teratogenic effects of aluminum-nitrate administration may result in rats given high oral doses that induce concomitant maternal toxicity.     

Effects of eflornithine hydrochloride (DFMO) on fetal development in rats and rabbits

Eflornithine hydrochloride (DFMO) is a highly selective, enzyme-activated, irreversible inhibitor of the enzyme L-ornithine decarboxylase (ODC). Because of its role in the biosynthetic pathway of polyamines, ODC is essential for the growth and development of newly implanted embryonic tissue. In order to assess its effect on embryonic growth and fetal development, at various stages of gestation, DFMO was administered in the drinking water to pregnant rats and rabbits at several concentrations (from 0.03% to 3.0%) and times (from days 7, 10, or 11 through days 18 or 19). Rats were killed on day 21 and rabbits on day 29 of pregnancy (day 1 = day of insemination), and the implantations and fetuses were examined. At a concentration of 1.0% (approximately 1,270 mg/kg/day) in rats and 3.0% (approximately 915 mg/kg/day) in rabbits, maternal food and water consumption and body weight gain were significantly reduced during the treatment period, and all implantations were aborted or resorbed. At lower doses (approximately 200-600 mg/kg/day) fetuses survived to term, though in reduced numbers, and a marked reduction in average fetal weight was seen. At levels of 60 mg/kg/day or lower, there were no deleterious effects to the dams or their offspring. Few malformations were detected at any dose level by gross teratologic examination; nor were any considered to have been drug induced because of their sporadic incidence. The embryotoxicity and severe growth retardation demonstrated by these studies verify that adequate polyamine levels are essential for normal embryonic and fetal development.     

Teratogenic effect of AY 9944 in rats: importance of the day of administration and maternal plasma cholesterol level

An inhibitor of cholesterol synthesis, AY 9944 (trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride) is teratogenic. A single dose of AY 9944 (50 mg/kg or 75 mg/kg) given to Wistar pregnant rats on the second, fourth, sixth, seventh, or eighth day of gestation induced malformations such as holoprosencephaly. They were often limited to isolated pituitary agenesis. The highest percentage of holoprosencephalic fetuses was found when AY 9944 was given on the fourth day of gestation. Whatever the dose and the day of administration, the lower the maternal plasma cholesterol level, the more frequent were holoprosencephalic fetuses. Therefore, it is suggested that the decrease in maternal plasma cholesterol level is at least one of the factors provoking holoprosencephaly.     

Lack of teratogenicity of trans-2-ene-valproic acid compared to valproic acid in rats

The teratogenicity of trans-2-ene-valproic acid (300 and 400 mg/kg) was compared with that of valproic acid (VPA; 300 mg/kg) and controls (corn oil) administered by gavage to Sprague-Dawley CD rats on embryonic (E) days 7-18. At the 300 mg/kg dose, trans-2-ene-VPA produced no change in maternal weight, number of implantations, proportion of resorptions, proportion of malformations, or fetal weight. By contrast, the same dose of VPA (300 mg/kg) reduced maternal weight during gestation, increased malformations (12.0% vs. 0.7% in controls), and reduced fetal body weight by 25.1%. An even higher dose of trans-2-ene-VPA (400 mg/kg) produced a reduction in maternal body weight during treatment and reduced fetal body weight (by 7.9%), but did not increase resorptions or malformations in the fetuses. On day E18, maternal serum drug concentrations of VPA were higher in the VPA-treated group compared with those of trans-2-ene-VPA in the trans-2-ene-VPA-treated groups at 1 hr posttreatment. At 6 hr posttreatment the reverse was seen. trans-2-ene-VPA may be absorbed more rapidly and distributed differently than VPA. Overall, the data support the view that trans-2-ene-VPA at equal or higher doses than VPA is not teratogenic in rats.     

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 and postnatal developmental studies of morphine in Sprague-Dawley rats

The teratogenic and postnatal developmental effects of morphine exposure during pregnancy were studied in Sprague-Dawley rats in three separate experiments using chronically implanted osmotic minipumps in order to avoid respiratory depression. In the first experiment, the teratogenic effects of three different morphine dosages were studied: a low dose (10 mg/kg/day), an intermediate dose (35 mg/kg/day), and a high dose (70 mg/kg/day). On day 5 of gestation, osmotic minipumps that deliver their contents at a constant rate for 15 days were implanted subcutaneously on the back of the rats. On day 20 of gestation, cesarean sections were performed, reproductive indices were determined, and fetuses were examined externally and then preserved for subsequent visceral and skeletal examinations. The pregnancy rate was significantly reduced at the intermediate and high doses to 57% and 6%, respectively (control, 83%). No teratogenic effects were observed at any dosage, but growth retardation was present in the intermediate-dose group. In the second experiment, postnatal survival of the offspring of dams treated with either normal saline, morphine (35 mg/kg/day), or the synthetic opioid, fentanyl (500 micrograms/kg/day) were studied. Offspring of morphine-treated dams had a significantly higher mortality rate, which peaked at 56% within 2 days. No effect was seen after fentanyl treatment. In the third experiment, pups of morphine-treated dams were cross-fostered by saline-treated dams; the postnatal mortality in offspring of morphine-treated dams remained high (62%). Our results indicate that doses of morphine up to 35 mg/kg/day delivered by osmotic minipumps are not teratogenic in rats but cause other adverse fetal effects that result in increased postnatal mortality.     

Perinatal death and respiratory apparatus dysgenesis due to a bis (dichloroacetyl) diamine

N, N1-bis (dichloroacetyl) diamine 1, 8-octomethylenediamine (WIN 18,446) is an experimental drug which was first investigated as a male contraceptive. It is soluble in lipid solvents but not in water. The administration of 1,200 to 1,600 mg/kg to pregnant rats on the tenth day of gestation produced multiorgan fetal malformations. Smaller doses, 400 to 800 mg/kg, especially if divided over 2 or 3 days, caused perinatal death. Thus, 60 to 100% of offspring of rats given WIN 18,446 on the tenth and 11th days of gestation died at birth or within 4 days (Taleporos et al., 78). The present study investigated such deaths. At doses of 200 mg/kg on day 10 or 50 mg/kg on days 10 and 11, 67% of offspring had defective or absent diaphragms, 48% had tracheobronchiomegaly with cystic lungs, and 67% had pleural hemorrhage. At doses of 100 mg/kg given on 1 day or 25 mg/kg each day for 2 days, 50% had tracheobronchiomegaly with cystic lungs and rudimentary acini. At lower doses (18.8 mg/kg X 2 or 12.4 mg/kg X 3), a majority of fetal lungs had rudimentary acini, thick septa, few capillaries, and wide cuffs of perivascular connective tissue. Thus, a chemical given during organogenesis produced dysgenesis of the respiratory apparatus. Varying the dose produced malformed lungs with persistently deficient acini which model such human lung faults as tracheobronchiomegaly (Mournier-Kuhn Syndrome; Mounier-Kuhn, '32), bronchiolar dysplasia (Wilson-Mikity Syndrome), and perinatal death with acinar failure resembling neonatal hyaline membrane disease.     

Action of the phenothiazine derivative methophenazine on prenatal development in rats.

Single doses of 100-400 mg/kg or multiple doses of 10 or 50 mg/kg of the phenothiazine derivative methophenzaine were given per osto Wistar rats at various times on the 7th-14th days fo gestation and the fetuses examined near term. Results indicated that methophenazine was mainly embryolethal when administered on the 8th-11th days, and was teratogenic at later times, producing types of malformations that depended on the day of treatment, the most susceptible period being the 13th and 14th days of gestation. Teratogenicity occurred only when the dosages were highly toxic to the pregnant rats. Ribovlavin given ip on the 14th day significantly reduced the embryolethal but not the teratogenic action of methophenazine.     

Developmental toxicity of pentostatin (2'-deoxycoformycin) in rats and rabbits

The developmental toxicity of the potent adenosine deaminase (ADA) inhibitor, pentostatin (2'-deoxycoformycin), was investigated in pregnant rats and rabbits administered daily iv doses during organogenesis. Rats received 0, 0.01, 0.10, or 0.75 mg/kg on gestation days 6-15 and rabbits received 0, 0.005, 0.01, or 0.02 mg/kg on gestation days 6-18 and maternal and fetal parameters were evaluated on gestation day 21 (rats) or 30 (rabbits). Live fetuses were examined for external, visceral, and skeletal malformations and variations. In rats, maternal body weight gain and food consumption were significantly suppressed at doses of 0.10 and 0.75 mg/kg during the treatment period but returned to control levels during posttreatment. Increased postimplantation loss and decreased numbers of live fetuses, litter size, and fetal body weight were observed at 0.75 mg/kg. A statistically significant increase in the incidence of vertebral malformations occurred at 0.75 mg/kg. The incidence of certain skeletal variations (extra presacral vertebrae, extra ribs, hypoplastic vertebrae) was also increased at 0.75 mg/kg. Ossification of cervical centra was reduced at 0.75 mg/kg compared with controls. In rabbits, marked maternal toxicity (death, body weight loss, and decreased food consumption) and reproductive toxicity (abortion and premature delivery) occurred in all pentostatin-treated groups. However, there were no significant effects on number of live fetuses, pre- or postimplantation loss, litter size, or fetal body weights in the animals with live litters. There was also no apparent increase in the incidence of malformations or variations in the live fetuses of pentostatin-treated rabbits. Thus, these studies demonstrate developmental toxicity of pentostatin in rats and rabbits, and teratogenicity in rats, at maternally toxic doses.     

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.     

Developmental and neurobehavioural toxicity study of arsenic on rats following gestational exposure

To characterize developmental and behavioral alterations induced by arsenic exposure, Albino rats were exposed to arsenic (0, 1.5, 3.0 and 4.5 mg/kg/day/po) from gestation day 8 to till parturition and the offspring were observed over the first 3 postnatal weeks, until they were weaned on post-natal day (PND) 21. Once the pups were delivered (PND0), the treatment was discontinued. All pups were assessed for physical development, reflex development, strength and motor coordination from standard neurobehavioural developmental test batteries beginning on PND1. Gestational administration of arsenic at tested dose levels, showed no significant changes in the day of appearance of eye opening, startle reflex, negative geotaxis and spontaneous alteration performance in comparison to the control group. The number of live fetuses, mean fetal body weight and percentages of resorptions or malformations per litter were not affected by arsenic exposure. No treatment-related malformations or developmental variations were noted at any exposure level, suggesting that arsenic exposure at this dose level did not adversely affect behavioural endpoints of developmental toxicity.     

Cardiopathic effects of dichloroacetate in the fetal Long-Evans rat.

Dichloroacetic acid (DCA) is a by-product of the chlorine disinfection of water and may occur in treated water at levels exceeding 100 micrograms/L. Previous studies revealed teratogenic effects, particularly heart malformations, at high doses (900-2,400 mg/kg given on days 6-15 of pregnancy). In a series of three studies, groups of 7-10 Long-Evans rats were dosed with 1,900 mg/kg of DCA on days 6-8, 9-11, or 12-15; with 2,400 mg/kg on days 10, 11, 12, or 13; and with 3,500 mg/kg on days 9, 10, 11, 12, or 13, in an attempt to determine the most sensitive period and further characterize the heart defect. In a fourth study, six dams were treated with 1,900 mg/kg of DCA days 6-15 of pregnancy, and 56 fetuses were harvested for light microscopy of the heart. Eight control fetuses from four litters were also examined. No heart malformations were seen in the groups treated with 1,900 mg/kg DCA days 6-8 but were present in the group treated on days 9-11 and 12-15, with the higher incidence occurring on days 12-15. Single doses of 2,400 mg/kg DCA given on days 10, 11, 12, or 13 resulted in a much lower incidence of cardiac malformations, which occurred only on days 10 and 12. The high dose of DCA (3,500 mg/kg) did not increase the incidence of heart defects but showed that dosing on day 9 as well as on days 10 and 12 would produce the defect. The defects seen were characterized as high interventricular septal defects (H-IVSD). Light microscopy showed that the defect was caudal to the semilunar valves, with the anterior right wall of the aorta communicating with the right ventricle. Another aspect of the defect is at the level of the semilunar valves, with the right cusp or sinus of Valsalva in communication with the right ventricle. The defects are discussed more fully and methods for further study suggested.     

Strain differences in teratogenic susceptibility to trypan blue between WM and BDIX rat strains

Female rats of WM (Wistar-Mishima)/Nem strain were mated with WM/Nem (group W) or BDIX/Nem males (group WB), and BDIX/Nem females were mated with BDIX/Nem (group B) or WM/Nem males (group BW). On day 8 of gestation, pregnant females were treated intraperitoneally with 1% aqueous solution of trypan blue at a dose of between 20 and 120 mg/kg of body weight. On day 20 of gestation, fetuses were examined for external, visceral, and skeletal malformations. In group W, fetal mortality increased dose dependently at doses higher than 20 mg/kg, and incidences of external, visceral, and skeletal malformations were significantly higher than control at doses of 30 mg/kg and more. In group B, fetal mortality and the incidence of external malformations were significantly higher than control only in the group treated with 120 mg/kg, and no significant increase of visceral and skeletal malformations was shown. It was confirmed that BDIX strain is much more resistant to trypan blue teratogenicity than WM strain. In group BW, nearly the same teratogenic effects were shown as in group W in terms of fetal mortality and incidence of malformations. However, in group WB, teratogenic effects were not so remarkable as in group BW, suggesting patroclinous effects in teratogenic susceptibility to trypan blue. In group BW, sex differences in teratogenic susceptibility were found; male fetuses were more susceptible to trypan blue than females.