DIFFERENTIAL MODULATION BY PROTEIN-KINASE-C OF PROGESTERONE-ACTIVATEDRESPONSES IN HUMAN SPERM

Progesterone exerts important effects on human spermatozoa by rapid no n genomic mechanisms of action. It has been demonstrated that processe s triggered by this steroid are dependent on the activation of calcium influx through the plasma membrane. Beside calcium, progesterone also induces a rapid plasma membrane depolarization that is dependent on a n influx of sodium through a putative progesterone-activated channel l ocated on the plasma membrane. In this study we show that protein-kina se C inhibition inhibits calcium influx activated by progesterone, whi le leaving the depolarizing effect of this steroid unchanged. These re sults may be explained by the existence of two progesterone receptors on human sperm plasma membrane, one responsible for calcium influx and modulated by protein-kinase C and the other selectively permeable to sodium that is not under protein-kinase C control. Alternatively, prot ein-kinase C inhibition might change ion selectively of a single proge sterone-activated channel, thus decreasing calcium permeability, while leaving sodium permeability unchanged. (C) 1995 Academic Press, Inc.