ACROSOME CONTENT RELEASE IN STREPTOLYSIN-O PERMEABILIZED MOUSE SPERMATOZOA

Sperm cell plasma membrane and the outer acrosomal membrane fuse profu sely during the acrosome reaction. The process is triggered by extrace llular signals that elicit several intracellular events leading ultima tely to membrane fusion. We have developed a streptolysin O permeabili zing protocol that selectively affects the spermatozoon plasma membran e without causing a significant loss of the acrosomal content. Most of the acrosomal acid phosphatase remained sperm-associated even after a 20 min incubation at 37 degrees C. However, the presence of 100 mu M Ca2+ in the incubation buffer stimulates the release of the enzyme. Th e reaction was followed biochemically, measuring the acid phosphatase activity released to the medium and morphologically by the binding of fluorescein isothiocynate-conjugated peanut agglutinin and by electron microscopy. The results show that the streptolysin O permeabilized sp ermatozoon is a promising model for studying the complex set of events mediating and regulating the acrosome reaction.