Binding of seminal vesicle proteins to the plasma membrane of rat spermatozoa in vivo and in vitro

The association of seminal vesicle (SV) proteins with rat spermatozoa has been studied in vivo and in vitro. SV proteins bind to the sperm plasma membrane after ejaculation but are removed progressively from the sperm plasma membrane in the female genital tract. Although some of these remain bound to spermatozoa when they reach the oviducts, they do not seem to be present at the time of fertilization. This could indicate a putative role for these SV proteins in pre-fertilization events. In addition, the binding of SV antigens was studied in vitro. It was observed that the ability to bind SV proteins is gained by the spermatozoa during epididymal maturation, and is first detectable in spermatozoa collected from the cauda epididymis. On the other hand, the binding is regulated by other proteins present in the ejaculate which are secreted by the coagulating glands. Experiments also showed that mouse spermatozoa are able to bind rat SV proteins, indicating that the binding is not a highly species-specific phenomenon.