Functional aspects of human sperm binding to the zona pellucida using the hemizona assay.

The hemizona assay (HZA) has facilitated investigations of sperm function in relation to zona pellucida binding. In this study, the authors examined: 1) the association between hyperactivated sperm motility and HZA binding; 2) the binding kinetics and efficiency of sperm from subfertile men; and 3) the influence of sperm freezing and thawing on binding capacity. For each HZA, a nonviable human oocyte was cut into equal zona hemispheres. The mean number of bound sperm and the incidence of hyperactivation were significantly greater for samples of sperm from fertile men compared with sperm from subfertile men (P less than 0.05). Subfertile sperm had a binding curve that paralleled the curve for fertile sperm, although the magnitude of binding was markedly reduced. Freezing and thawing of sperm from fertile samples impaired their capacity to bind to the zona pellucida. The HZA binding efficiency was reduced by 30%, although the binding curves for fresh versus frozen samples remained parallel.