Abstract: Objective To investigate the impact of succinate dehydrogenase (SDH) on the modulation of human sperm functions. Methods The isolated human sperm were co-incubated with different concentrations (10, 20, 40 mmol/L) of SDH inhibitor disodium malonate for one or two hours. The activity of the SDH was measured by commercially available reagent kit, while the protein level of the SDH catalytic subunit SDHA was determined through Western blot analysis. Sperm functions were analyzed:1)The impact of disodium malonate on important motility parameters of un-capcitated sperm including progressive motility rate (PR), total motility (TM), average pathvelocity (VAP)and the ability of capacitated sperm to penetrate viscous media were be assessed using a computer aided semen analysis system. 2) Effect of disodium malonate on sperm survival rate was evaluated using the Eosin-Nigrosin microscopy. 3) The incidence of acrosome reaction in capacitated sperm was be detected by PSA-FITC staining assay following disodium malonate treatment. Results Disodium malonate had no effect on expression of SDH catalytic subunit SHDA protein in human sperm. However, it inhibited the catalytic activity of the SDH, sperm forward motility, total motility, and the ability of sperm to penetrate viscous media. These inhibitory effects were positively correlated with the concentration of disodium malonate. Furthermore, disodium malonate had no any influence on the occurrence of spontaneous acrosome reaction in capacitated sperm. Conclusions Disodium malonate impairs human sperm motility by inhibiting succinate dehydrogenase activity.

Key words: succinate dehydrogenase, disodium malonate, sperm function, sperm motility