Metabolism of Pyriproxyfen. 3. In Vitro Metabolism in Rats and Mice

Abstract

In vitro metabolism of pyriproxyfen [4-phenoxyphenyl (RS)-2-(2-pyridyloxy)propyl ether, Sumilarv] by several tissues of rats and mice was investigated. Most of the major metabolites of pyriproxyfen observed in studies of in vivo metabolism were formed by liver microsomes incubated in vitro with β-NADPH for both species. No sex-related differences were observed in mouse microsomes in major in vitro metabolic reactions, these being hydroxylation at the 4-position of the terminal phenyl ring, hydroxylation at the 5-position of the pyridyl ring, and cleavage of the propyl pyridyl or propyl phenyl ethers. On the other hand, in rat microsomes there were significant sex-related differences in these major metabolic reactions except for cleavage of the propyl phenyl ether. All of the gender-specific reactions, in which cytochrome P450 enzymes were involved, were inhibited by antisera against male-specific rat P450 CYP2C11 or CYP2C13. Therefore, the results strongly imply that the 2C family of cytochrome P450 is in...