Interconversion between Fenthion and Fenthion Sulfoxide in Goldfish, Carassius auratus

Abstract

The in vitro metabolism of fenthion, an insecticide, was examined in fish, focusing on the interconversion between fenthion and its sulfoxide (fenthion sulfoxide). When fenthion was incubated with hepatopancreas microsomes of goldfish, Carassius auratus, in the presence of NADPH, the oxidized metabolite, fenthion sulfoxide was formed, but not fenthion sulfone. The oxidase activity was inhibited by SKF 525-A, and partly by α-naphthylthiourea. In contrast, fenthion sulfoxide was reduced back to fenthion by the hepatopancreas cytosol of goldfish in the presence of 2-hydroxypyrimidine, an electron donor for aldehyde oxidase. The activity was markedly inhibited by menadione, an inhibitor for aldehyde oxidase. The interconversion appears to be mediated mainly by the cytochrome P450 system and aldehyde oxidase.