NADPH cytochrome P-450 reductase in rat, mouse and human brain

NADPH cytochrome P-450 reductase (P-450 reductase), an essential component of the cytochrome P-450 mono-oxygenase system, has been estimated in rat and mouse brain, and seven human brains obtained at autopsy. The ratio of cytochrome P-450 to P-450 reductase is lower in the rat and mouse brains (2.5-4.0) as compared to the respective livers (10.0-11.0). The rat and mouse brain P-450 reductase were immunologically similar to the rat liver P-450 reductase as examined by immunochemical inhibition, Ouchterlony double diffusion and immunoblot. The antisera to rat liver P-450 reductase inhibited rat brain aminopyrine N-demethylase activity to the same extent as NADPH cytochrome c reductase, suggesting that the level of P-450 reductase controls the rate of this cytochrome P-450 mediated activity. The human brain NADPH cytochrome c reductase exhibited regional variation, maximal activity being observed in the brain stem region. Immunochemical inhibition and immunoblot studies revealed immunological cross-reactivity between rat liver reductase and human brain medulla, while none was observed in cortex or cerebellum. Immunocytochemical studies on human brain medulla using antisera to rat liver P-450 reductase indicated localization of the P-450 reductase in neuronal cell body.