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.

Determination of the developmental toxicity potential of butoxypropanol in rabbits after topical administration.

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

The effects of dietary iron supplementation on the toxicity of piroctone olamine in the growing rat.

Weanling Charles River CD rats of both sexes were fed 300 mg/kg/day of Piroctone Olamine, an anti-bacterial agent, and were supplemented with 0, 50, 100 or 200 ppm dietary iron as FeSO4.7H2O for six weeks. However, analytical data indicated that Piroctone was degraded in the diet so that the rats received only 225 mg/kg/day. The rats given Piroctone Olamine without iron gained significantly less body weight and ate significantly less feed than controls, with the effect being more pronounced in the males. They also developed severe microcytic, hypochromic anemia. The rats supplemented with all three levels of dietary iron grew at a rate similar to controls. The rats supplemented with 50 ppm dietary iron had anemia with all of the hematological iron-associated factors being significantly depressed. The 100 ppm supplement restored all hematologic factors to normal in the females, but slight reductions remained in the males. The 200 ppm supplement of iron restored all parameters to values similar to the controls in both sexes. These results suggest that the mechanism of the toxicity of Piroctone Olamine is the prevention of dietary iron absorption by in situ chelation.

Studies of the developmental toxicity of polycarboxylate dispersing agents.

Three linear polycarboxylate compounds, two linear polyacrylates (90,000 MW and 4,500 MW) and one linear polyacrylate-maleate copolymer (12,000 MW), were tested for their teratogenic potential in female Sprague Dawley rats. These polymers, which were tested as sodium salts, are used as dispersing agents in detergent formulations at levels of 1-5%. All compounds were administered by gavage during organogenesis (days 6-15 of pregnancy). No adverse effects on development were seen with any of the three compounds at any of the doses tested. The highest dose, and therefore the minimum no-effect dose, for the three linear polymers was 1125 mg/kg/day for the 90,000 MW polyacrylate, 3000 mg/kg/day for the 4,500 MW polyacrylate, and 6670 mg/kg/day for the polyacrylate-maleate copolymer. Based on these data, these compounds are not developmentally toxic, even at very high dose levels.

Effect of a high systemic background level of vitamin A on the teratogenicity of all-trans-retinoic acid given either acutely or subacutely.

Groups of 12 Charles River CD virgin female rats were either supplemented with 25,000 IU/kg of vitamin A palmitate or not during the first 8 days of pregnancy and in the first experiment given a single dose of either 5 or 10 mg/kg of all-trans-retinoic acid (RA) on day 9 of pregnancy. In a second experiment, similar groups were given either 4 or 8 mg/kg RA daily from day 6 through day 15 so that each treatment with RA was given to vitamin A supplemented rats or nonsupplemented rats. The high systemic background of vitamin A increased the teratogenicity of the 10 mg/kg dose of RA given on day 9 by 50%, but reduced the teratogenicity of the 8 mg/kg dose given on days 6-15. The reasons for this paradox are discussed and related to the human propensity to self-medicate with megadoses of vitamins.

A two-generation reproductive and developmental toxicity study of sucrose polyester.

Sucrose polyester (SPE) is a mixture of hexa-, hepta- and octa-esters of fatty acids with sucrose, and has physical and organoleptic properties similar to those of conventional dietary fats. Because SPE is neither absorbed nor metabolized it forms a bulk lipid phase in the small intestine, resulting in effects on the absorption and enterohepatic circulation of lipid-soluble materials, such as cholesterol and fat-soluble vitamins. Such effects could potentially alter the physiology of animals to the extent of interfering with reproduction and/or the normal development of the embryo/foetus. To determine the likelihood of such phenomena, Sprague-Dawley rats were continuously fed SPE at dietary levels of 1, 5 or 10% along with controlled levels of vitamins A and E for two generations, with a reproductive and a teratogenic phase in each generation. Body-weight gain of rats fed SPE was comparable to that of the controls throughout the study, but feed consumption increased with increasing levels of SPE. Pregnancy or lactation had no effect on these growth patterns. Throughout the study, SPE had no deleterious effect on mating, conception, embryonic development, foetal or post-natal viability, or on post-natal growth. Nor was there any treatment-related histopathology. Thus, it is concluded that SPE would not represent a reproductive or teratogenic hazard to human consumers of products containing SPE.

The effects of prenatal retinoic acid on the viability and behavior of the offspring.

Three experiments were done in Charles River rats to assess the effects of various doses of retinoic acid given at different periods of pregnancy on the postnatal function of the offspring. In the first study doses of 5 mg/kg of body weight were given on days 8-10, 11-13, or 14-16. In the second study, doses of 2.5 or 5 mg/kg were given on days 11-13 or 14-16. In the third study, doses of 2, 4 or 6 mg/kg were given on days 14-16. Five mg/kg given on days 11-13 resulted in significant postnatal mortality, while the viability at all other doses and periods was not affected. The weights of the pups at birth and weaning were normal except in the first study when the pups from dams given 5 mg/kg on days 14-16 were smaller than controls at weaning. The pups from dams treated with 4, 5 or 6 mg/kg consistently showed a delayed response to negative geotropism and auditory startle was delayed in two of the studies at 6 mg/kg. Hyperactivity in preweaning rats tested in photo-cell cages was seen only in the first study, but open-field hyperactivity occurred in all three studies at doses of 4 mg/kg or above. The M-maze performance of the rats from groups dosed with 4, 5 or 6 mg/kg on days 8-10 or 14-16 and the ones dosed with 2.5 mg/kg on days 11-13 was poorer than controls. No differences were seen in either photo-cell or open-field activity at 42 days, but in the final experiment, the rats from the 6 mg/kg group were hyperactive at 100+ days in running wheels. The rats in the 6 mg/kg group performed more poorly at active avoidance and were hypoactive after an amphetamine challenge. These studies show that retinoic acid given prenatally induced functional deficits in the offspring at doses below the "no-effect" level for producing morphological defects and suggests that retinoic acid may be a good model compound for such studies.

Fertility and teratogenic studies of diethylene glycol monobutyl ether in rats and rabbits.

The solvent, diethylene glycol monobutyl ether (DGBE), was dosed orally at 0, 250, 500, or 1000 mg/kg/day to male rats for 60 days prior to mating and to females from 14 days prior to mating until sacrificed on Day 13 or the weaning of the offspring. Untreated males were bred to treated females and vice versa. One-half of each group of females was sacrificed on Day 13 of gestation and the uterine contents were examined. The remaining females delivered their young and the offspring were followed to weaning. The solvent had no adverse effect on fertility in either sex and no adverse effects on embryos, fetuses, or neonates, except that the mean pup weights were reduced slightly during the later stages of lactation among the offspring of the females dosed with 100 mg/kg/day. Pregnant rabbits treated topically with the solvent applied to the dorsal skin at 0, 100, 300, or 1000 mg/kg on Days 7-18 of gestation exhibited a dose-dependent mild skin irritation but no other signs of toxicity. No adverse effects were seen on intrauterine survival or on the incidence of fetal malformations.

An industrial developmental toxicologist's view of behavioral teratology and possible guidelines.

Many events or studies, such as the Minimata episode, during the past three decades have shown that prenatal insults can have lasting effects on the postnatal functioning of the offspring. These have been duplicated in animal models, and animal studies have been extended to other compounds with the eventual goal of being able to establish the risk in humans of neurological damage a priori from prenatal exposures. However, behavioral tests are not standardized with many of them lacking sensitivity, and are so vulnerable to environmental factors, that little confidence can be placed in their ability to predict risk to the human at this time. More research is needed to develop better tests and an understanding of their significance to humans before they are useful in regulatory toxicology.

A reproduction/teratology study of brewed and instant decaffeinated coffees.

Sprague-Dawley rats of both sexes were given, in place of their drinking water, full-strength or 50 or 25% dilutions of either brewed or instant decaffeinated coffees for about 6 mo from weaning. These levels are equivalent to the human consumption of about 50, 25, or 12 cups of coffee per day. Controls were given either distilled water, or full-strength or a 25% solution of regular brewed coffee. The rats were bred twice after 91 d to assess reproduction and teratogenicity. The parent animals given decaffeinated coffees and 100% regular coffee drank less than the rats given water, while the rats given 25% regular coffee drank more. No effects on body weight gain or feed efficiency were seen, except that the group given 100% regular coffee gained significantly less weight than the water controls. None of the coffee treatments had a significant effect on reproductive characteristics such as conception rate, number born, or number weaned. During the second pregnancy, no significant effects from the coffee treatments were seen on early embryotoxicity measured in dams sacrificed on d 13 of pregnancy or fetal toxicity in dams sacrificed on d 21. No significant fetal abnormalities due to any of the coffee treatments were observed in either soft-tissue or skeletal examinations, although there was a significant increase in unossified sternebrae in the fetuses from dams given the full-strength regular coffee.

The absorbability by rats of various triglycerides of stearic and oleic acid and the effect of dietary calcium and magnesium.

Rats were fed diets in which the triglycerides contained oleate and stearate as the sole fatty acids. These fatty acids were esterified to specific positions on the glycerol molecule. The triglycerides were 1-stearoyl diolein (SOO), 2-stearoyl diolein (OSO), 2-oleoyl distearin (SOS), 1-oleoyl distearin (OSS), and triolein (OOO). The absorbability of the fatty acid component was measured by the fat balance technique. Two diets, one sufficient and the other deficient in calcium and magnesium, were used. The oleic acid of all of the triglycerides was absorbed almost completely. The following values for the absorbability of the stearate component in the presence and in the absence of the divalent cations were obtained: OSO 98 and 99; SOO 55 OAND 96; SOS 37 and 70; OSS 59 and 60. These patterns of absorbability are discussed in relation to the pathway of triglyceride digestion. If the stearic acid is esterified at the 2-position of the triglyceride, the resulting 2-monostearin is well absorbed. If it is esterified at the 1- or 3-position, it is released as free stearic acid, and in the presence of calcium and magnesium it is poorly absorbed.

Teratology studies of a mixture of tallow alkyl ethoxylate and linear alkylbenzene sulfonate in rats and rabbits.

A mixture of 55% tallow alkyl ethoxylate sulfate (TAE3S) and 45% of linear alkylbenzene sulfonate (LAS) was fed to two generations of rats at dietary levels of 0.1, 0.5 or 1.0%. The rats were fed the surfactant mixture either continuously or during the organogenesis (days 6-15) period of six pregnancies. In addition, pregnant New Zealand rabbits were given 50, 100 or 300 mg/kg doses of the surfactant mixture by intubation on days 2-16 of gestation during a single pregnancy. No adverse effects were noted on conception, fetal viability or post-natal survival in either generation of rats. There were no statistical differences among the groups of rat fetuses taken by Caesarian section and examined for birth defects. Of 1210 rat fetuses, the overall incidence of abnormal young was 9.0%. Similarly, no adverse effects were seen in rabbits treated with the surfactant mixture. Of 855 rabbit fetuses, 5.7% were abnormal, but the incidences of defective fetuses in the test groups were not significantly different from those in controls. Thus, no test related effects were seen on reproduction or embryonic development in either animal species.