Further characterization of a model system for the study of human epididymal physiology and its relation to sperm...

Some preliminary speculations about the possible participation of epididymal antigens in sperm function may be supported by the above data. On the one hand, the reduction in the amount of antigens and their abnormal localization on spermatozoa from infertile patients may be coincident with our view about participation of epididymal antigens in the development of zona pellucida binding ability and fertilizing capacity by spermatozoa during maturation. This hypothesis is derived from experiments showing that immature hamster spermatozoa gain their ability to recognize and bind to zona pellucida and to penetrate homologous oocytes when exposed to preparations enriched in androgen-dependent epididymal secretory proteins or preincubated in conditions that favor their interaction with these proteins. Supporting our viewpoint for such a role in humans is evidence showing the progressive development of the ability to interact with hamster denuded oocytes as human spermatozoa pass along the epididymis. On the other hand, the apparent correlation between the loss of epididymal antigens during capacitation and the increased fertilization of human oocytes in vitro may be reminiscent of the removal of a decapacitation or acrosome stabilizing factor known to occur in many species and that must be removed prior to fertilization. Pending further understanding of their physiological role, the androgen-dependent epididymal proteins may become a useful marker of epididymal function and/or of sperm capacitation in humans. Within this context, we wish to stress the potential value of the model system that we have developed for the study of human epididymal physiology.