Vol. 28, Issue 3, 348-353, March 2000

Selective Involvement of Cytochrome P450 2D Subfamily in In Vivo 4-Hydroxylation of Amphetamine in Rat

Michael Y. L. Law,¹ Matthew H. Slawson, and David E. Moody

Center for Human Toxicology, Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah

The cytochrome P450 (P450) 2D subfamily catalyzes ring hydroxylation of amphetamines. We tested the hypothesis that P450 2D is selectively involved in amphetamine 4-hydroxylation. Urinary elimination of 4-hydroxyamphetamine and amphetamine was determined in male Sprague-Dawley rats pretreated with P450 inducers and inhibitors. The urinary 24-h metabolic ratio (amphetamine/4-hydroxyamphetamine) was not affected by the inducers 3-methylcholanthrene, isosafrole, phenobarbital, ethanol, pregnenolone--carbonitrile, and clofibrate. Isosafrole did, however, increase amphetamine elimination along with urine volume. Urinary elimination of 4-hydroxyamphetamine was significantly decreased by, and the metabolic ratio increased by, the inhibitors 1-aminobenzotriazole, CCl₄, quinidine, quinine, and primaquine. Diallyl sulfide and troleandomycin had no effect. In rat liver microsomes primaquine was shown to be an inhibitor of 2D activity. Urine 4-hydroxyamphetamine content correlated strongly (r² = 0.989) with microsomal P450 2D activity in parallel-treated rats. These studies also substantiate that 4-hydroxylation of amphetamine is selectively performed by the P450 2D subfamily in the rat.