EPIDERMAL GROWTH-FACTOR INDUCES ACROSOMAL EXOCYTOSIS IN BOVINE SPERM

At the time of fertilization mammalian spermatozoa undergo a Ca2+-depe ndent exocytotic event, which is known as the acrosome reaction (AR). We describe here that EGF-receptor (EGFR) is localized in the head of bull spermatozoa and that epidermal growth factor (EGF) can induce the occurrence of the AR in its typical dose-dependent manner. Previously we showed that protein kinase C (PKC) is involved in the cascade lead ing to AR in bull spermatozoa. Here, we show that PKC is involved in t he mechanism in which EGF exerts its effect on AR, These findings toge ther with our results which show inhibition of AR by tyrosine-phosphor ylation inhibitors, indicate that ejaculated bull sperm contain a typi cal 170-kDa EGFR which is active in the mechanism leading to AR.