EFFECT OF NATURAL ANTIOXIDANTS, SUPEROXIDE-DISMUTASE AND HYDROGEN-PEROXIDE ON CAPACITATION OF FROZEN-THAWED BULL SPERMATOZOA

Bovine spermatozoa from frozen-thawed semen are sensitive to lipid per oxidation. Vitamin E protects sperm membrane against oxidative damage. Sperm capacitation produces structural changes on the plasma membrane . Reactive oxygen species could be involved in the capacitation proces s. The aim of this work was to study the influence of natural antioxid ants on the plasma membrane and the influence of reactive oxygen speci es during bovine sperm capacitation. Sperm samples were frozen in a st andard diluent, with and without vitamin E (1 mg ml(-1)). Heparin (60 mu g ml(-1)) was used as a sperm capacitation inductor. Sperm capacita tion was evaluated by chlorotetracycline assay. Lipid peroxidation was determined by the 2-thiobarbituric acid assay. A diminution of thioba rbituric acid reactive substances was observed in sperm samples frozen with vitamin E (P < 0.05). The addition of vitamin E to the freezing diluent had no effect on the capacitated pattern (P > 0.05). When vita min E and vitamin E + vitamin C were added to the capacitation medium, a significant decrease in the percentage of capacitated spermatozoa ( P < 0.05) was observed in both cases. The addition of superoxide dismu tase (0.1 mg ml(-1)) or H2O2 (50 mu M) in the incubation medium, decre ased the percentage of capacitated spermatozoa (P < 0.05). Vitamin E p rotects the plasma membrane against lipid peroxidation during sperm ca pacitation, and the presence of superoxide anion would be necessary fo r frozen-thawed bull sperm capacitation.