Covalent binding of carbaryl (1-naphthyl-N-methyl-carbamate) to rat liver microsomes in vitro

Abstract

Enzyme mediated binding of carbaryl (1-naphthyl-N-methylcarbamate) to rat hepatic microsomes occurred in vitro in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and oxygen and was inhibited by nitrogen, carbon monoxide, reduced glutathione, cysteine, N-ethyl maleimide, and 2-diethylaminoethyl-2,2'-diphenylvalerate-HCl (SKF 525-A). Binding was markedly increased, 2- to 3-fold, by pretreatment of animals with phenobarbital or 3-methylcholanthrene and appeared to be dependent on the production of an active metabolite which was formed oxidatively in liver microsomes by cytochrome P-450 mixed-function oxidases. SDS-polyacrylamide disc gel electrophoresis of ether-extracted, solublized microsomes and the distribution of radioactivity after Pronase digestion, treatment with 1-fluoro-2,4-dinitrobenzene, and extraction with ethyl acetate and ether at pH 9 and 1 indicated that the radiolabeled products were covalently bound to amino acid residues of microsomal protein.