Glucose is not essential for the occurrence of sperm binding and zona pellucida-induced acrosome reaction in the mouse

Glucose is necessary, in some species, for successful fertilization, but its role in the different gamete functions has only been documented partially. In this study we have examined the progression of mouse spermatozoa through the oocyte investments in order to determine which steps require glucose. Evidence is presented of glucose involvement during this sequence of events, since in-vitro fertilization was inhibited in glucose-free medium even when spermatozoa were capacitated in the presence of glucose. Access to the zona pellucida was not inhibited in the absence of glucose, suggesting that capacitation, progressive motility and zona binding of spermatozoa do not depend on the presence of an extracellular glycolysable substrate. However, zona penetration was prevented in the absence of glucose. Most importantly, the zona pellucida-induced acrosome reaction was found to occur in glucose-free medium. It is proposed that hyperactivated motility, which has been described to require glucose in the Literature, may be the precise process responsible for the failure of spermatozoa to enter the perivitelline space.