The metabolism of 4-methoxy-beta-choloro styrene by liver microsomal monooxygenases.

The compound 4-methoxy-β-chloro styrene has been chosen as a model substrate for microsomal monooxygenases to study the relative rates of O-demethylation, ring hydroxylation and covalent binding by the suggested epoxide intermediate. The phenolic products were identified by g.c.-m.s. and the covalent binding was measured as non-extractable ¹⁴C-labeled metabolites. The monooxygenation by rat liver microsomes resulted mainly in an O-demethylation reaction and the relative extent of covalent binding was dependent on the pretreatment of the animals with either phenobarbital or 3-methylcholanthrene. Ring hydroxylation occurred in position 3 and was measurable only after pretreatment with 3-methylcholanthrene. It was concluded that each cytochrome P450 has an individual pattern of detoxifying vs toxifying pathways. The species of cytochrome P450 mainly responsible for covalent binding was very little affected by metyrapone and had a rather low affinity for the substrate.