Heparin-induced release of DNA template restrictions in human sperm zinc-depleted nuclei

The addition of heparin to human sperm zinc-depleted nuclei releases DNA template restrictions. Spermatozoa depleted of zinc were assayed for (3H-methyl), thymidine incorporation was observed (27,500 +/- 1,248 dpm of 3H methyl-thymidine). Sperm cells incubated in the presence of 10 mg/ml of soybean trypsin inhibitor shows no effect in sperm nuclear swelling or in the release of DNA template restrictions. This process runs in a parallel fashion to the nuclear swelling induced by heparin, suggesting that swollen nuclei might be the source of DNA template. This was confirmed by autoradiographic studies, since all the sperm cells whose nuclei were judged swollen by morphological criteria also appeared labeled. The fact that there was no need for ATP generating system or of exogenous DNA polymerase emphasized the control role that zinc plays in the physiology of the human spermatozoa.