THE EXTRAGENOMIC ACTION OF PROGESTERONE ON HUMAN SPERMATOZOA

Progesterone exerts an extragenomic action on human spermatozoa, inclu ding a calcium transient in the acrosomal domain of these cells via pu tative receptor sites located on the sperm surface. The calcium transi ent can be visualized in >80% of spermatozoa treated with this steroid although their capacity to respond to the calcium signal is heavily d ependent on their capacitation status, Capacitation is, in turn, depen dent on a redox-regulated increase in tyrosine phosphorylation that pr imes the spermatozoa in such a way that the primary calcium influx ind uced by progesterone is followed by a chloride efflux and the onset of secondary calcium oscillations, The way in which these changes precip itate a biological response and the nature of the molecular pathways o rchestrating these events are currently unknown.