Stabilization of cytochrome P-450 in hepatocytes by free radical scavengers of different nature.

The stabilizing effects of various free radical scavengers on cytochrome P-450 content in isolated rat hepatocytes were studied. It has been shown that incubation of hepatocytes in vitro leads to spontaneous degradation of cytochrome P-450 to accumulation of lipid peroxidation products, e.g. malonyl dialdehyde (MDA). Activation of lipid peroxidation in hepatocyte suspensions by the Fe2+-ADP+NADPH system results in acceleration of cytochrome P-450 degradation due to a considerable increase in the rate of MDA accumulation. There is experimental evidence about the relationship between these two processes in hepatocytes, i.e. addition of 2-ethyl-6-methyl-3-hydroxypyridine, 2, 6-di(tert)butyl-4-hydroxytoluene, and 1, 2, 3-tri-hydroxybenzene to the incubation medium leads to inhibition of lipid peroxidation and stabilization of cytochrome P-450. 2, 6-di(tert)butyl-4-hydroxytoluene is a much more effective inhibitor of lipid peroxidation in hepatocytes and a more potent stabilizer of cytochrome P-450 than the water soluble 1, 2, 3-trihydroxybenzene and 2-ethyl-6-methyl-3-hydroxypyridine. Hydroxylation of 3,4-benz (alpha) pyrene in hepatocytes is also concomitant with a decrease of MDA accumulation and cytochrome P-450 degradation. Free radical scavengers of phenolic type, both exogenously added or endogenously formed via oxidative metabolism of hydrophobic substrates are powerful stabilizers of cytochrome P-450 in liver cells.