LIPID AND ANTIOXIDANT CHANGES IN SPERMATOZOA AND SEMINAL PLASMA THROUGHOUT THE REPRODUCTIVE PERIOD OF BULLS

The lipid compositions and associated antioxidant capacities of sperma tozoa and seminal plasma from bulls were examined at the beginning, mi ddle and end of their reproductive period. The reduction in concentrat ion and motility of spermatozoa associated with ageing was accompanied by a large decrease in lipid concentrations within the seminal plasma ; this change in lipid concentration was accompanied by an increase in the proportion of phospholipid. By contrast, the proportion of phosph olipids in the spermatozoa was significantly reduced. The major phosph olipid fractions within both the spermatozoa and seminal plasma were p hosphatidyl choline and phosphatidyl ethanolamine. With increasing age there was a large decrease in the proportion of phosphatidyl ethanola mine and a commensurate increase in that of phosphatidyl choline withi n the spermatozoa and seminal plasma. These major changes in phospholi pids were accompanied by a decrease in the amount of phosphatidyl inos itol and an increase in that of cardiolipin in both spermatozoa and se minal plasma. The reductions in the proportions of phosphatidyl ethano lamine were accompanied by extensive reductions in the content of the major polyunsaturated fatty acids, arachidonic 20:4 (n-6) and docosahe xaenoic 22:6 (n-3); there was a decrease also in the concentration of 22:6 (n-3) in phosphatidyl choline. The changes in lipid composition o wing to ageing were associated with a marked reduction within the semi nal plasma of the major antioxidant enzyme systems, glutathione peroxi dase and superoxide dismutase.