Effects of platelet activating factor on mouse sperm function

Platelet activating factor (PAF) has been implicated in a variety of reproductive processes. This study was designed to investigate the effect of PAF and the specific PAF receptor antagonist, CV-3988, on capacitation and the acrosome reaction in mouse spermatozoa using an in vitro fertilization (IVF) system. When spermatozoa were preincubated for 30 min in medium containing PAF (10(-7) to 10(-11) M), a significant increase in the fertilization rate with both cumulus-free and zona-free oocytes was observed. In contrast, treatment of the spermatozoa with 10(-5) M CV-3988 caused a significant decrease in both sperm motility and fertilization rates with zona-intact and zona-free oocytes. This suppression was reversed by the addition of PAF. Furthermore, the acrosome reaction was enhanced by PAF treatment of spermatozoa in a dose-dependent manner. This stimulation of the acrosome reaction by PAF required the presence of calcium ions in the medium. While 10(-5) M CV-3988 inhibited the acrosome reaction, the inhibition was also reversed by the addition of PAF. These results suggest that PAF can stimulate not only the capacitation process but also the acrosome reaction, both of which are dependent on extracellular calcium.