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


Department of Obstetrics and Gynecology, Osaka University Medical School, 2-2, Yamadaoka, Suita, Osaka, 565, Japan.


PROBLEM: To evaluate the “effect of nitric oxide in the seminal plasma on sperm motility. METHOD: Seminal plasma concentrations of NO2, 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 NO2 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 NO2 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.