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

The acrosome reaction is a specialized exocytotic process. In the mous e there is compelling evidence thar receptor-mediated activation of GT P-binding proteins by factors in the zona pellucida of oocytes is a ce ntral event in the acrosome reaction. Sereral reagents are able to aff ect GTP-binding proteins directly, bypassing the receptor-ligand step for activation. We have assessed the effect of several of these compou nds on human spermatozoa, monitoring cell vitality and the acrosome re action simultaneously using the triple-stain technique. GTP gamma S an d aluminium fluoride complexes promote sperm activation very efficient ly; amphiphilic peptides capable of activating G(o) and G(i), also eli cit the acrosome reaction. The results indicate that activation of het erotrimeric GTP-binding proteins is sufficient to trigger acrosome exo cytosis in human spermatozoa.