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

Abstract

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.

Nuclear Chromatin Decondensation of Human Sperm: A Review

“…Since albumin does not cleave disulfide bridges, and in the meantime does decondense sperm [31], it seems that zinc depletion unmasks free thiols which would, in turn, destabilize the S-S bridges, provoking the decondensation of the nucleus [33]. The role of these free thiols, endogeneous within the sperm, seems to be ascer-*Deficient spermatogenesis [ 11 tained since thiol-blocking agents (copper, iodosobensoate, chloromercuribensoate, iodoacetamide) induce a 100% resistance to SDSiEDTA [32].…”

“…Normal seminal plasma stabilizes sperm depleted in zinc (341 or sperm from men with an impaired prostatic function, whereas calcium or magnesium have no such effect [31]. Zinc, but not calcium, inhibits the effects of heparin on the plasmatic membrane and the nucleus [37]; 80 pM zinc stabilizes 90% of sperm subjected to SDS [31]. Subjects with a low seminal zinc have a higher percentage of spontaneously decondensed sperm [22].…”

“…Disodium ethylene tetraacetate (EDTA) or 4 % albumin, which chelate divalent cations, increase the action of decondensing reagents [30, 371. Normal seminal plasma stabilizes sperm depleted in zinc (341 or sperm from men with an impaired prostatic function, whereas calcium or magnesium have no such effect [31]. Zinc, but not calcium, inhibits the effects of heparin on the plasmatic membrane and the nucleus [37]; 80 pM zinc stabilizes 90% of sperm subjected to SDS [31].…”

“…Therefore, zinc seems to be a temporary inhibitor of an intrinsic mechanism of decondensation, a mechanism further reactivated in the female genital tract by zinc depletion and probably part of the capacitation process [27,31,371. Since albumin does not cleave disulfide bridges, and in the meantime does decondense sperm [31], it seems that zinc depletion unmasks free thiols which would, in turn, destabilize the S-S bridges, provoking the decondensation of the nucleus [33].…”

Seminal Plasma Zinc and Magnesium in Infertile Men

“…The presence of high levels of Zn in the seminal plasma exerts adverse effects on spermatozoal motility and morphology [4, 131, on the preservation of intact cellular membranes [12], and on the stability of sperm nuclear chromatin structure [14, 151. Similarly, it has been shown that Zn ions adversely affect the morphology of the tail of the spermatozoa in bulls as well as in man [16].…”