Effects of PDC-109 on bovine sperm functional activity in presence or absence of heparin

PDC-109, a heparin-binding protein (from the seminal vesicles) that binds to sperm surface phospholipids at ejaculation, may modulate several aspects of sperm activity. The objectives of the present study were to determine: (1) in the presence or absence of heparin, the effects of exogenous PDC-109 on sperm motility (Makler chamber), viability (Hoechst 33258) and membrane functional integrity (hypoosmotic swelling test) of bovine spermatozoa; (2) the role of PDC-109 as a capacitation-inducing factor; and (3) its ability to induce the acrosome reaction (fluorescein staining). After 4-h capacitation in the presence of heparin, the addition of PDC-109 (0.5, 1.5 or 3.0mg/ml) significantly decreased the percentages of motile, progressive, and viable cells; these effects were also detected in the absence of heparin. However, PDC-109 elicited a twofold increase (from 14 to 28%) in the proportion of acrosome-reacted spermatozoa, but only in the presence of heparin. Progesterone (10 microM) or angiotensin II (100 or 1000 nM) stimulated the acrosome reaction after capacitation in the presence of PDC-109 without heparin (from 10 to 17, 23 and 22%, respectively). In conclusion, PDC-109 appears to modulate sperm functional activity, with some effects manifest in the absence of heparin.