[An in vitro study, in the human, of the relation between epididymal spermatozoa and the zona pellucida]

The ability of non capacitated human spermatozoa recovered from the caput, corpus and cauda epididymis, to bind the isologous or heterologous (rat) zona pellucida has been investigated. Experiments were performed with cold immobilized spermatozoa to avoid differences resulting from motility into the epididymis. Comparison with similar investigations in the ram (works and review of Fournier-Delpech and Courot, 1987) lead to conclude that human spermatozoa are: 1) able to bind to the human zona in the proximal epididymis; 2) unable to recognize heterologous zona at any level of the epididymis. From this, a strict species-specificity of the sperm-zona interactions exists in the proximal epididymis, in the human. By contrast, in the ram, sperm-zona binding develops in the epididymis iso- or hetero-specifically. Restricted species specificity appears in the ejaculate only. Data are in agreement with species specificity of gametes interactions in the human (Bedford, 1977). Such results could contribute to explain in vitro or in vivo fertilization with sperm originating from the middle epididymis (Temple-Smith et al., 1985; Soychsman and Bedford, 1986).