Induction of cytochrome p‐450 isozymes by mirex and chlordecone

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Abstract
The effect of the insecticides, mirex and chordecone (Kepone), on the cytochrome P‐450 monooxygenase system in C57BL/6N mouse liver microsomes was studied. Mice were treated intraperitoneally with low (6 mg/kg) and high (30 mg/kg) doses of mirex and chlordecone in corn oil for 2 days. For comparison, mice were also treated with either phenobarbital (PB) or 3‐methylcholanthrene (3‐MC). All treatments significantly increased the hepatic microsomal P‐450 content over that of controls. Benzphetamine N‐demethylase, ethoxyresorufin O‐deethylase, benzo[a]pyrene hydroxylase, and acetanilide hydroxylase activities were also determined. Mirex and chlordecone resembled phenobarbital with respect to the induction of monooxygenase activities. Immunoquantitation with antibodies to purified P‐450 IIB1 (Pb‐induced P‐450) and P‐450 IA1 (3‐MC‐induced P‐450) indicated that mirex and chlordecone induced P‐450 IIB1 in a dose‐dependent manner. The high dose of mirex also induced a small amount of a protein cross reacting with the antibody to IA1. The induction of this isozyme did not, however, contribute significantly to the monooxygenase activities measured.