Maternal toxicity and teratogenicity of tellurium dioxide in the Wistar rat: relationship to pair-feeding.

Tellurium dioxide (TeO2) induces hydrocephalus, edema, exophthalmia, ocular hemorrhage, umbilical hernia, undescended testes and small kidneys in day 20 Wistar rat fetuses when administered s.c. to pregnant dams from gestational day 15 to 19. At doses of 500 mumole/kg or greater, a 100% incidence of these findings and a reduction in maternal weight gain were observed. A pair-fed study at the dose of 500 mumole/kg of TeO2 was conducted to establish if the effects of tellurium were a result of a reduction in food intake or other maternal toxic responses. Two additional control groups of rats receiving tellurium or vehicle were fed ad libitum. After a comparable maternal weight gain from day 0 to 15, weight gain was significantly reduced in the treated groups and the pair-fed control. There was a reduction of fetal weight in the treated groups (p less than 0.01) and in the pair-fed control (p less than 0.02). There was a 100% incidence of the above anomalies in the litters of the two treated groups, but none in the pair-fed and control groups. No histological alterations other than a mild centrolobular fatty change in the liver were detected in the other organs from the tellurium exposed dams. Thus, tellurium induces both maternal toxicity and teratogenic effects in the rat where the teratogenicity is not mediated by alterations in the diet.