DDT, heptachlor, chlordane, and parathion toxicity in adult, newborn, and phenobarbital-treated newborn rats
Pesticide lethality and effect of phenobarbital (PB) treatment on pesticide lethality were compared between age groups. DDT, heptachlor (H), chlordane (C), and parathion (P)induced lethality were determined in adult (A), newborn (NB), and PB-treated NB rats. Adult Sprague-Dawley rats, 100 to 120 g, and 5-day post-partum NB rats, 10 to 12 g, were used in the study. PB, 40 mg/kg, was administered for 4 days and the pesticide administered on day 5. Median lethal dosage (MLD) was calculated from the number of deaths at the end of a 7-day period. DDT MLD is 224 mg/kg for A and 2356 mg/kg for NB. PB treatment of NB rats enhances lethality of DDT to a MLD of 1344 mg/kg. Heptachlor MLD is 71 mg/kg for A and 531 mg/kg for NB. PB treatment of NB rats enhances lethality of H to a MLD of 133 mg/kg. Chlordane MLD is 344 mg/kg for A and 1121 mg/kg for NB. PB pretreatment of NB rats enhances lethality of C to a MLD of 539 mg/kg. Thus, toxicity of DDT, H, and C is 5 to 10 times less in NB when compared to A, but PB treatment enhances the toxicity of all three pesticides in the NB. Parathion MLD is 8.8 mg/kg in A and 1.9 mg/kg in NB. However, PB treatment of NB rats antagonizes P lethality to a MLD of 4.8 mg/kg. Toxicity of DDT, C, H, and P is age dependent and altered by PB treatment. Although PB treatment antagonizes P toxicity it enhances DDT, C, and H toxicity. (Supported by NIH Grants ES 00267 and ES 00782.)