Properties of microsomal enzyme systems that reduce N-hydroxyphentermine

The reduction of N-hydroxyphentermine was studied in liver microsomes isolated from rat, guinea pig, and rabbit. The reduction requires a NADPH-generating system and was inhibited by oxygen and carbon monoxide. In the rat, the reduction was increased by phenobarbital pretreatment. Kinetic analysis of the reductase activity in rat liver microsomes suggests that the reduction of the hydroxylamine is mediated by at least two enzyme systems, one of which is a CO-sensitive system inducible by phenobarbital.