Elevated Nitric Oxide Concentration in the Seminal Plasma of Infertile Males: Nitric Oxide Inhibits Sperm Motility

PROBLEM : To evaluate the effect of nitric oxide in the seminal plasma on sperm motility. METHOD : Seminal plasma concentrations of NO 2 - , a stable end product of nitric oxide, of 108 males of infertile couples and 15 proven fertile donors were measured and compared with spermatogram parameters. Motile sperm was incubated with a nitric oxide-generating drug, sodium nitroprusside, for 6 hr in the absence or presence of oxyhemoglobin, an inhibitor of nitric oxide. RESULTS : The NO 2 - concentration in the seminal plasma was 6.58±0.56 μM in 26 infertile males with leukocytospermia, 5.51±0.25 μM in 82 infertile males without leukocytospermia, and 3.91±0.16 μM in 15 controls. There was a significant correlation between the NO 2 - concentration and sperm motility. Sodium nitroprusside reduced the sperm motility in a dose-and time-dependent manner and its reduction was completely inhibited by the addition of oxyhemoglobin. CONCLUSION : These findings indicate that nitric oxide concentration in the seminal plasma of infertile males is elevated and that nitric oxide is an inhibitor of sperm motion.