Effects of phenobarbital, chlordane, and oxytetracycline on DDT excretion in rats.

The effects of phenobarbital, chlordane, and oxytetracycline on DDT biliary excretion in rats were evaluated. The relationship between the increase of biliary flow induced by these drugs and the elimination of DDT was also evaluated. Phenobarbital (2.5 mg/ml) was fed to rats in their drinking water and chlordane (200 mg/kg) was added to the diet over a period of 3 days; oxytetracycline (200 mg/kg/day) was fed to rats orally for 8 days. After these treatments [14C]DDT was administered orally to anesthetized rats and then the bile was collected through cannulation of the bile duct. The data obtained show that phenobarbital and chlordane decrease zoxazolamine paralysis time and increase liver weight and biliary flow. Both drugs increase biliary excretion of [14C]DDT and decrease [14C]DDT levels in plasma; oxytetracycline increases zoxazolamine flow significantly. Oxytetracycline does not change biliary excretion of [14C]DDT but decreases the blood levels of the insecticide; and pretreatment of animals with phenobarbital, chlordane, and oxytetracycline does not significantly change [14C]DDT concentration in bile. These data demonstrate that the increased biliary excretion of DDT depends on the rate of bile elimination.