Enhancement of Anilinep-Hydroxylation by Acetone in Rat Liver Microsomes

Abstract

1. Acetone (0.8 M) enhanced the p-hydroxylation of aniline about 3-4 fold when added to the incubation mixture. Only inhibition in hydroxylation of 3,4-benzpyrene or N-demethylation of ethylmorphine was observed. 2. Phospholipase C treatment of rat liver microsomes decreased aniline p-hydroxylation about 20%. The enhancing action of acetone vanished after such a treatment. 3. Acetone diminished the type II binding of aniline. In the presence of acetone, low concn. of aniline produced a type I difference spectrum with rat hepatic microsomes. With higher concn. of aniline a type II spectral change was obtained. This indicates that aniline, a well-known type II substrate, can also interact with the type I binding site of cytochrome P-450. Correlation between the type I spectral change and activation of aniline p-hydroxylation is suggested. Acetone itself elicited a spectral change with rat liver microsomes resembling a type II difference spectrum. 4. Acetone partly reversed the inhibition produced by aniline on NADPH-cytochrome P-450 and NADPH-cytochrome c reductase. This contributes also to the activation of aniline p-hydroxylation by acetone.