OXIDATIVE METABOLISM OF ALDRIN AND DIHYDROALDRIN BY HOUSEFLIES HOUSEFLY MICROSOMES AND PIG LIVER MICROSOMES AND EFFECT OF INHIBITORS

Dihydroaldrin undergoes hydroxylation at the C6-position (or the equivalent C7-position) in both pig liver and housefly microsomes to give a mixture of 6-exo- and 6-endo- hydroxydihydroaldrin. The oxidative metabolism of aldrin and dihydroaldrin therefore resembles the epoxidation and hydroxylation of certain similarly related steroids. The lower toxicity of dihydroaldrin, compared with aldrin, to normal houseflies is partly correlated with dihydroaldrin hydroxylation. Although there are differences between the two species, the microsomal enzymes responsible for epoxidation and hydroxylation in any one species are similar with regard to pH dependence, stability and response to inhibitors. The competitive inhibition of aldrin epoxidation by dihydroaldrin is consistent with these compounds acting as alternative substrates for the same enzyme, though conclusive evidence for this is lacking. © 1969.