p-Hydroxylase and N-demethylase activities of cytochrome P450 system, NO-synthase activity and the intensity of nitric oxide and superoxide anion production in mitochondrial, postmicrosomal and microsomal cellular fractions were studied in mouse liver under conditions of retinoid stores absence.It is determined, that under conditions of retinoid stores absence the activation of NO-synthase is occurring with decreased p-hydroxylase activity of cytochrome P450 system. The results of the generation intensity analysis showed the level of NO and О2- in liver mitochondrial fraction of knock-out mice, and changes in NADPH-dependent О2- production in microsomal fraction of mouse liver cells.