Influence of antioxidants on the peroxidative swelling of mitochondria in vitro.

To clarify the role of prooxidative processes during in vitro swelling of freshly isolated rat liver mitochondria, the influence of different antioxidants and free-radical scavengers was tested. Ascorbate below 10 mmol/L without externally added Fe2+ acted as a prooxidant and enhanced swelling. Higher concentrations in the presence of Fe2+ showed antioxidant properties and a decrease in swelling and lipid peroxidation. Swelling was abolished by alpha-tocopherol and reduced to 50% by butylated hydroxytoluene. Glutathione supplementation decreased both swelling and lipid peroxidation. Oxidized glutathione caused swelling without any effect on peroxidation. Hydrogen peroxide, cumene hydroperoxide and t-butyl hydroperoxide caused progressive decreases in glutathione and reduced niacinamide coenzyme levels, suggesting prooxidative changes. Dithiothreitol was found to abolish this effect. Thus, antioxidants reverse superoxide-induced mitochondrial swelling and lipid peroxidation in vitro.