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The Effect Of Tocopherol In Biological Membranes Is A Result Of Cooperation With Cytochrome b5

Z.S.Agadjanyan, M.V.Ivanova, L.F.Dmitriev

Lipid peroxidation was studied in liposomes and liver microsomes at the enzymatic and nonenzymatic (cumene hydroperoxide-dependent) induction of the process. The consumption of tocopherol, redox state of cytochrome b5 and the level of superoxide in addition of malonic dialdehyde formation were measured under different incubation conditions. At cumene hydro-peroxide-initiated microsomal oxidation it was shown that formation of lipid hydroperoxides is prevented by α-tocopherol in the presence of NADH only and superoxide was produced in membranes in this case. The antioxidative effect of α-tocopherol was lost in the absence of NADH or in the presence of mersalyl - inhibitor of NADHcytochrome b5 reductase. The ability of HADH to prevent free radical oxidation of the microsomal membranes was explained with regard to the following reactions: LOO• + e → LOO- , interaction of anion LOOwith α-tocopherol giving rise to replacement of oxygen in oxidizing fatty acid by H-atom and release of superoxide.