Effect of zinc on decondensation of human spermatozoa nuclei by heparin.

Swelling sperm nuclei were assayed, exposing them to the combine action in increasing amounts of seminal plasma 0.1-1.0 ml (124 +/- 21 micrograms of Zn++/ml). An inhibition of almost 30% in the swollen spermatozoa nuclei was observed with 0.1 ml of seminal plasma (12 micrograms of Zn++/ml) reaching to 71% with 74-124 micrograms of Zn++/ml. Inactivated seminal plasma (boiling) induced the same percentage of inhibition (73%) than normal seminal plasma. Dialyzed seminal plasma (31 micrograms of Zn++/ml) produced an inhibition of 88% of swollen spermatozoa nuclei, the same percentage produced with 30-35 micrograms of zinc ions (ZnCl2). Previous release of sperm zinc by preincubation with EDTA 6 mM changed the decondensation kinetics, making sperm nuclei more susceptible to the action of the glycosaminoglycan. No effect was observed in the presence of calcium ions. Therefore, zinc, among its several physiological roles, may act as a nuclear chromatin stabilizer.