Enzyme induction in the housefly: The specificity of the cyclodiene insecticides

Abstract

Eleven cyclodiene compounds, including the insecticides aldrin, dieldrin, heptachlor, and endrin, were compared as inducers of microsomal oxidases in a cyclodieneresistant strain of the housefly. All of the compounds except dihydroisodrin caused increases in enzyme activity. The epoxide members of the group appeared to be more effective inducers than their olefin precursors. Isodrin and endrin were effective at approximately 1 300 th the dose of the other compounds tested although neither compound enhanced enzyme activity as much as the others in the group. The maximum increase in enzyme activity was approximately 100% for aldrin and about 30% for isodrin and endrin. There was no additive effect when each of the compounds was combined with dieldrin in the induction treatments. In addition to microsomal epoxidation and hydroxylation, O-demethylation was enhanced by the cyclodiene treatments. Furthermore, DDT dehydrochlorinase, a nonmicrosomal enzyme, was increased as much as 137% by the treatments. The results indicate that within this group of compounds there are some structural requirements for activity but that the overall effect on enzyme activity is rather nonspecific.