PROGESTERONE ACTION ON THE HUMAN SPERM SURFACE IS POTENTIATED BY AN EGG-ASSOCIATED ACROSIN ACTIVATOR

The progesterone-induced Ca2+ influx and acrosomal exocytosis in human sperm are recently described examples of non-genomic steroid action o n the cell surface. These progesterone effects are known to be inhibit ed by synthetic protease inhibitors. In this study we tested a hypothe sis that a physiological activator of the sperm protease acrosin modul ates the sperm response to progesterone. It was found that the activat or augments the amplitude of the progesterone-induced Ca2+ transient a nd accelerates the progesterone-induced acrosomal exocytosis. These ob servations suggest a physiological significance of the modulation of n ongenomic steroid effects by protease regulators.