Enhanced Fc Receptor Expression In Sea Urchin Spermatozoa By Platelet-Activating Factor

Abstract

Platelet-activating factor (PAF) is a signaling phospholipid that has a variety of reproductive roles, e.g. sperm capacitation and the acrosome reaction (an exocytotic process). PAF’s mechanism action involves G-protein receptor activation induction of intracellular calcium, which enhances sperm motility. In nonreproductive cells, the Fc receptor (FcR) functions in ligand-triggered transmission signals across the membrane which alters secretion, exocytosis, and increased intracellular calcium. This study looked at the impact of PAF on FcR expression in sea urchin spermatozoa. Sea urchin sperm were exposed to exogenous PAF (10-7M; 15 minutes) and evaluated for FcR activity via flow cytometry. A significant (P=0.01) difference (64.30%) in FcR wave activity between the PAF (mean 3.286) and control (2.0) groups was observed. Within waves, there were more (83.31%) high points (crests) in the PAF (mean 1.571) group than the control (mean 0.857) group. Similarly, there were more (49.96%) low (troughs) points in the PAF (mean 1.714) group than the control (mean 1.143) group. This is the first report to demonstrate a relative positive change in spermatozoa FcR expression when exposed to PAF. The FcR functions in ligand-triggered transmission of PAF via a G-protein coupled receptor mediated pathway leading to physiological alterations. Provided the known mechanism of action of PAF on spermatozoa physiology, the data suggests that the interaction of PAF and FcR play a pivotal role in sperm activity and fertilization potential.