Microsomal enzyme activity in perfused rat liver

The activities of microsomal enzymes were observed during perfusion of livers isolated from both normal and phenobarbital treated rats. The hydroxylation of aniline and the O-demethylation of p-nitroanisol did not decrease substantially (by 10 per cent only) in the 9000 g fraction prepared from livers perfused for 4 hr.N-demethylation of aminopyrine was reduced by 60 per cent in the same experimental conditions. A similar decrease of N-demethylation was also observed when livers were isolated from animals treated with phenobarbital. The content of cytochrome P-450 in the microsomes was stable during a 4-hr perfusion of isolated liver. The decrease of N-demethylation of aminopyrine could be partly restored by the simultaneous infusion of nicotinic acid, which is a precursor of NAD and NADP biosynthesis.