A positive role for the superoxide anion in triggering hyperactivation and capacitation of human spermatozoa

Capacitation of human spermatozoa is essential for fertilization, and is characterized visually by hyperactivated motility. We have investigated whether reactive oxygen species could induce these two events in human spermatozoa. The addition of xanthine + xanthine oxidase + catalase (X+XO+CAT: generation of superoxide anion and removal of hydrogen peroxide) and foetal cord serum (FCS), a known biological inducer of capacitation and hyperactivation, to spermatozoa, induced levels of hyperactivation (15.4 +/- 1.6% and 8.0 +/- 1.0%, respectively) which were significantly higher than that of controls (5.4 +/- 0.6%). The hyperactivation measured was part of the capacitation process. Furthermore, the addition of superoxide dismutase prevented the capacitation and hyperactivation induced by X+XO+CAT or by FCS. These results suggest that the superoxide anion may be involved in capacitation and hyperactivation of human spermatozoa.