REAGENTS THAT ACTIVATE GTP-BINDING PROTEINS TRIGGER THE ACROSOME REACTION IN HUMAN SPERMATOZOA

The acrosome reaction is a specialized exocytotic process. In the mouse there is compelling evidence thar receptor-mediated activation of GTP-binding proteins by factors in the zona pellucida of oocytes is a central event in the acrosome reaction. Sereral reagents are able to affect GTP-binding proteins directly, bypassing the receptor-ligand step for activation. We have assessed the effect of several of these compounds on human spermatozoa, monitoring cell vitality and the acrosome reaction simultaneously using the triple-stain technique. GTP gamma S and aluminium fluoride complexes promote sperm activation very efficiently; amphiphilic peptides capable of activating G(o) and G(i), also elicit the acrosome reaction. The results indicate that activation of heterotrimeric GTP-binding proteins is sufficient to trigger acrosome exocytosis in human spermatozoa.