Background: Intracellular calcium and proton concentrations are important factors for activating human sperm. Calcium ion (Ca2+) enters sperm through voltage-dependent calcium channel of sperm (CatSper). Proton was extruded from sperm through voltage-gated proton channel (Hv1). In the present study, the selective inhibitors of the CatSper and Hv1 channels, NNC 55-0396 (NNC) and zinc ion, respectively, were used to investigate functions of these channels.
Methods: Normal semen samples (n=24) were washed and diluted to 20×106sperm/ml. The diluted sample was divided into 8 groups, containing Ham's F-10 (the control group), 2 μM NNC, 1 mM ZnCl2 and NNC+Zn. The other 4 groups were the same as above, except that they contained 1 μM progesterone. The computer assisted analysis was done by VT-Sperm 3.1 to determine the percentage of motile sperm and sperm velocity. Acrosomal status was monitored by FITC-PSA and viability assessed by Eosin-Y staining. Statistical comparisons were made using ANOVA followed by Tukey post hoc test. The p<0.05 was considered significant.
Results: The percentage of viable and motile sperm, curvilinear velocity and other parameters of motility was reduced in all groups containing NNC, zinc and NNC+ zinc. Progesterone-induced acrosome reaction was abolished by each of these inhibitors. The combination effect of NNC plus zinc on motility and progesterone-induced acrosome reaction was not stronger than NNC by itself.
Conclusion: CatSper and Hv1 channels play a critical role in human sperm function and viability. It seems that a functional relationship exists between CatSper and Hv1 channels.
Keywords: Acrosome reaction; CatSper channel; Hv1 channel; Progesterone; Sperm motility.