Selective involvement of cytochrome P450 2D subfamily in in vivo 4-hydroxylation of amphetamine in rat

The cytochrome P450 (P450) 2D subfamily catalyzes ring hydroxylation of amp hetamines. We tested the hypothesis that P450 2D is selectively involved in amphetamine 4-hydroxylation. Urinary elimination of 4-hydroxyamphetamine a nd amphetamine was determined in male Sprague-Dawley rats pretreated with P 450 inducers and inhibitors. The urinary 24-h metabolic ratio (amphetamine/ 4-hydroxyamphetamine) was not affected by the inducers 3-methylcholanthrene , isosafrole, phenobarbital, ethanol, pregnenolone-alpha-carbonitrile, and clofibrate. Isosafrole did, however, increase amphetamine elimination along with urine volume. Urinary elimination of 4-hydroxyamphetamine was signifi cantly decreased by, and the metabolic ratio increased by, the inhibitors 1 -aminobenzotriazole, CCl4, quinidine, quinine, and primaquine. Diallyl sulf ide and troleandomycin had no effect. In rat liver microsomes primaquine wa s shown to be an inhibitor of 2D activity. Urine 4-hydroxyamphetamine conte nt correlated strongly (r(2) = 0.989) with microsomal P450 2D activity in p arallel-treated rats. These studies also substantiate that 4-hydroxylation of amphetamine is selectively performed by the P450 2D subfamily in the rat .