Differential effects of fasting and nicotinic acid on various enzymatic activities of the 9,000 g fraction of the perfused rat liver.

Perfused livers obtained from rats fasted for 24 or 48h show a marked impairment of the N-demethylation (substrate aminopyrine) without major changes of the O-demethylation (p-nitro anisol) and hydroxylation (aniline). The infusion with nicotinic acid restored N-demethylation but it inhibited O-demethylation and hydroxylation.