WHITE BLOOD-CELLS CAUSE OXIDATIVE DAMAGE TO THE FATTY-ACID COMPOSITION OF PHOSPHOLIPIDS OF HUMAN SPERMATOZOA

The lipid composition of the sperm membrane has been shown to exert a significant effect upon the functional quality of spermatozoa. We have studied the effect of induced peroxidation and of the presence of pol ymorphonuclear white blood cells (WBCs) on the fatty acid composition of the phospholipids of human spermatozoa. The spermatozoa were fracti onated by a discontinuous Percoll gradient in two fractions (47% and 9 0% Percoll). Induced peroxidation of spermatozoa was assessed by deter mining the production of thiobarbituric acid reactive substances (TBAR S), mostly malondialdehyde, after incubation with ferrous sulphate and sodium ascorbate as a promoter of peroxidation. TEARS production afte r induction of peroxidation was correlated with the abundance of polyu nsaturated fatty acids (PUFA) (r = 0.68, p < 0.0001), with the double bond index (r = 0.72, p < 0.0001), and with the oxidative potential in dex (r = 0.73, p < 0.0001) of fatty acids of phospholipids. In compari son with samples containing > 1 x 10(6) WBCs/mL, those with < 1 x 10(6 ) WBCs/mL contained higher proportions of PUFA (90% Percoll, p < 0.05; 47% Percoll, p < 0.05), total omega 3 fatty acids (90% Percoll, p < 0 .05; 47% Percoll, p < 0.001), docosahexaenoic acid (90% Percoll p < 0. 05, 47% Percoll, p < 0.05), and double bond index (90% Percoll, p < 0. 05; 47% Percoll, p < 0.001). In addition, mean melting point was signi ficantly lower (90% Percoll, p < 0.05; 47% Percoll, p < 0.001) in samp les with < 1 x 10(6) WBCs, indicating higher membrane fluidity. The in crease of TBARS production by spermatozoa after incubation with the xa nthine-xanthine oxidase system and/or ferrous sulphate as promoter of peroxidation was associated with a significant decrease of PUFA. Incub ation of spermatozoa with WBCs, with or without activation by phorbol eater, decreased the PUFA (p < 0.05). Also, TEARS production was incre ased (p < 0.01) after activation of WBCs with phorbol ester. Our data provide evidence that oxidative stress induced by WBCs has a damaging effect on the polyunsaturated fatty acids of sperm phospholipids which may result, amongst other effects, in decreased membrane fluidity.