RESUMO
<p><b>OBJECTIVE</b>To explore the effect of nitric oxide (NO) on human sperm capacitation and acrosome reaction (AR).</p><p><b>METHODS</b>Different concentrations of sodium nitroprusside (SNP) were added to the sperm suspension from 48 healthy fertile men, and the suspension was incubated in 1 x Earle at 37 degrees C for 1 hour. Progesterone was used to induce AR for 15, 30, 45 and 60 min, and then acid phosphatase (ACP) activity in the suspension before and after capacitation and at different time of AR was measured by p-nitrophenyl sodium phosphate assay. In the meantime, sperm motile parameters were assayed by CASA to observe sperm capacitation and AR.</p><p><b>RESULTS</b>ACP activity and sperm motile parameters increased in the 50 approximately 100 nmol/L NO concentration group, showed no significant variation in the 150 approximately 200 nmol/L group, and decreased in the 250 approximately 300 nmol/L group.</p><p><b>CONCLUSION</b>NO can facilitate sperm capacitation, AR and sperm motile parameters in low concentration and suppress them in high concentration. ACP activity assay of sperm is an objective and reliable method to evaluate sperm capacitation and AR in whole sperm population.</p>