Peroxidative breakdown of phospholipids in human spermatozoa, spermicidal properties of fatty acid peroxides, and protective action of seminal plasma.

Aerobic incubation of human spermatozoa in the presence of catalytic amounts of ascorbate and ferrous ion results in rapid peroxidative breakdown of sperm phospholipids and fatty acids; most strongly affected are phosphatidyl ethanolamine, ethanolamine plasmalogen, and docosahexanoic acid. Both peroxidation of the endogenous sperm phospholipid and the concurrent loss of motility can be fully prevented, but not reversed, by an "antiperoxidant" factor present in human seminal plasma. Exogenously applied lipid peroxides are powerfully spermicidal. Washed human spermatozoa, at a concentration normally present in semen, treated with as little as 30 nmoles of lipid peroxide/ml become irreversibly immotile within a few minutes. The antiperoxidant factor present in human seminal plasma effectively counteracts the toxic effect of exogenous peroxidized fatty acids upon human spermatozoa, but is unable to restore motility lost by lipid peroxide action.