In-vitro capacitation of epididymal spermatozoa with heparin and gelatin binding buffalo seminal plasma proteins

Capacitation is an important process in bovine sperm maturation and is an obligatory step prior to fertilization. Upon ejaculation, a group of gelatin binding proteins (GBPs) and heparin binding proteins (HBPs) of seminal plasma binds to the sperm surface with membrane choline phospholipids of epididymal sperm. These proteins potentiate the sperm capacitation with heparin and high density lipoproteins (HDL). This study was undertaken to see the capacitation response with the HBPs and GBPs. Washed buffalo epididymal sperms were incubated with heparin (10 mu g/ml) in the presence of HBPs and GBPs @ 10, 20, 30, 40, 50 and 60 mu g/ml. The percentage of capacitated sperm was evaluated after the induction of acrosome reaction with lysophosphatidylcholine (100 mu g/ml) from 0 to 6 h. Both HBPs and GBPs acted in a similar way in the induction of acrosome reaction. The difference between treated group and control group was significant (P<0.05). The highest value of acrosome reacted sperm was seen in HBPs 40 mu g (75.6 +/- 0.6), followed by 30 mu g (73.8 +/- 0.6), 20 mu g(65.6 +/- 0.5), 10 mu g (57.3 +/- 0.7), 50 mu g (55.0 +/- 0.6) and 60 mu g (52.5 +/- 0.4). Similar trend was also observed in GBPs group, the highest value was recorded in 40 mu g (77.2 +/- 0.9) followed by 30 mu g (75.4 +/- 0.5), 20 mu g (67.6 +/- 0.3), 10 mu g (58.7 +/- 0.4), 50 mu g (54.2 +/- 0.5) and 60 mu g (52.5 +/- 0.4). At 6 h of incubation, acrosome reacted sperm percentage in proteins treated groups differed with each concentration and with control, It can be concluded that the addition of HBPs and GBPs enhances the capacitation responses and best dose level was 40 mu g of protein in HBPs as well as GBPs groups for induction of acrosome reaction.