Importance of spermatozoal zinc as temporary inhibitor of sperm nuclear chromatin decondensation ability in man.

Nuclear chromatin decondensation (NCD) of ejaculated human spermatozoa was studied in vitro. Spermatozoa subjected to membrane disintegration induced by the detergent sodium dodecyl sulphate (SDS) were found to undergo NCD if previously or afterwards treated with substances known to deplete the spermatozoa of zinc (albumin and EDTA). Zn2+, but not other, "prostatic" cations (Ca2+, Mg2+), inhibited the experimentally induced NCD and the NCD of spermatozoa from men with impaired prostatic function. It is suggested that the human spermatozoon has an intrinsic mechanism for NCD, that is preserved by temporary zinc inhibition and might be reactivated by zinc removal within the female genital tract.