Pyridine nucleotide involvement in rat hepatic drug metabolism: pyridine nucleotide kinetics of aniline parahydroxylation.

Apparent kinetic constant (NADPH) have been calculated for NADPH-cytochrome P450 reductase and parahydroxylase in the presence of aniline with hepatic microsomes from both phenobarbital pre-treated and untreated rats. The addition of NADH gave similar stimulation of both aniline parahydroxylation and NADPH-cytochrome P450 reductase activity in the presence of aniline. It is proposed that the increase in aniline metabolism with NADH is due to an increase in the NADPH-cytochrome P450 reductase activity which is rate limiting in microsomes from both phenobarbital and untreated rats.