Effects of seminal plasma on cooling-induced capacitative changes in boar sperm

Porcine seminal plasma (SP) has been shown to contain factors that have a decapacitative or capacitation-inhibiting effect on sperm. The objectives of the present study were to compare the capacitative changes observed in cooled sperm with those seen in sperm after in vitro capacitation and to determine whether SP could prevent these changes. Sperm were subjected to incubation or to slow cooling under noncapacitating or capacitating conditions. The effect of SP on protein tyrosine phosphorylation and the ability of the sperm to undergo an acrosome reaction (AR) were determined. Cooled sperm displayed an increased level of tyrosine phosphorylation and a higher percentage of induced AR sperm compared to incubated sperm. The addition of SP inhibited the number of ARs that occurred during incubation and cooling. These results suggest that cooling of sperm augments the capacitative changes in sperm, and that SP contains a factor(s) that effectively prevents these changes.