TREATMENT OF HUMAN SPERMATOZOA WITH SEMINAL PLASMA INHIBITS PROTEIN-TYROSINE PHOSPHORYLATION

It has long been known that seminal plasma contains factors that influ ence the fertilizing capacity of spermatozoa in many different ways. H owever, little is understood of the biochemical cascades triggered whe n spermatozoa and seminal plasma interact. In this study, we examined how incubation with seminal plasma affected protein tyrosine phosphory lation in human spermatozoa. Increased protein tyrosine phosphorylatio n is a hallmark of sperm capacitation in several mammalian species, in cluding human. Seminal plasma blocks protein tyrosine phosphorylation when added to washed, non-capacitated spermatozoa. Removal of seminar plasma and incubation in capacitating medium led to partial recovery o f the tyrosine phosphorylation cascade. Addition of seminal plasma to a suspension of spermatozoa previously incubated for 5 h under capacit ating conditions decreased the lever of tyrosine phosphorylation on al l proteins in a dose-dependent manner. In this case, the phosphotyrosi ne signal did not increase upon removal of seminal plasma followed by overnight incubation in fresh capacitating media, indicating that remo val of seminal plasma was necessary but not sufficient for protein tyr osine phosphorylation to occur. These results indicate that human semi nal plasma contains factors that influence the tyrosine phosphorylatio n status of human spermatozoa.