Mouse Liver Microsomal Lipid Peroxidation and Antioxidant Effect of α-Tocopherol at the Low Oxygen Concentration

Abstract

Mouse liver microsomal lipid peroxidation and antioxidant effect of α-tocopherol at the low oxygen concentration close to that in the cells (20-50 μM) was examined. The endogenous α-tocopherol level in liver microsomes of mice fed a vitamin E-deficient diet was 50 ng/mg protein. The level of thiobarbituric acid-reactive substances (TBARS) of the microsomal suspension on treatment with ADP/Fe(II) ion in Tris-HCl buffer (pH 7.5) at 37°C and at 270 μM O₂ gradually increased to reach a plateau at 14 nmol/mg protein after 60 min. The maximum level of TBARS was decreased to 6 nmol/mg protein at 34 μM O₂, indicating that lipid peroxidation was suppressed to about 1/2 at the limited O₂ concentration. The 50% inhibition concentration of the exogenously added α-tocopherol against the TBARS formation was almost linearly decreased as the O₂ concentration decreased, 2.8 μM α-tocopherol at 270 μM O₂ and 0.2 μM α-tocopherol at 34 μM O₂. Above results indicate that the degree of lipid peroxidation is lower and the antioxidant effect of α-tocopherol is much higher at the limited O₂ concentration than those at the atmospheric O₂ concentration.