Effects of piperine on hamster sperm capacitation and fertilization in vitro

The effect of piperine on the fertilizing ability of hamster sperm was investigated in vitro. Sperm were incubated in a capacitation medium for 3 h prior to co-incubation with hamster eggs in a fertilization medium for another 3 h. Addition of 0.18-1.05 mM piperine to the capacitation medium reduced both the percentage of eggs fertilized and the degree of polyspermia in a dose-dependent manner. When piperine was added to the fertilization medium alone, a significant reduction in fertilization was observed only at high doses (0.70-1.05 mM). The presence of piperine in the capacitation medium inhibited the acrosome reaction in a dose-dependent manner but had no effect on sperm motility, whether this was measured quantitatively or qualitatively. Piperine also inhibited the influx of calcium into sperm during capacitation. It is suggested that such an inhibition might be a major cause of a reduction of the acrosome reaction and the subsequent impairment of fertilizing ability of sperm.