Seminal platelet-activating factor.

Platelet-activating factor (PAF; 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphorylcholine) is a potent signaling phospholipid with pleiotropic biologic activities. Since its discovery more than 30 years ago, numerous investigators have documented its presence in a variety of tissues. PAF and its receptors are present both in somatic and reproductive cells. PAF appears to be critical for many of the events surrounding fertilization, early preimplantation embryo development, implantation, and embryo development. PAF is present in the sperm of many mammalian species including humans. It is synthesized, metabolized, and used by sperm. PAF may in fact be one biomarker for sperm capacitation. Endogenous PAF concentrations are directly correlated to sperm motility, forward progression, fertilization, and implantation and pregnancy rates in humans and other mammalian species. Exogenous PAF improves pregnancy rates in human intrauterine inseminations. Although the exact mechanism for PAF as it relates to sperm function is unclear, its importance is substantial.