Effects of nitric oxide on human spermatozoa activity, fertilization and mouse embryonic development

This study was conducted to investigate the effects of nitric oxide (NO) on human sperm activity, human sperm-oocyte fusion and mouse embryonic development. Results showed that various concentrations of NO synthase blocker, N(omega)-nitro-L-arginine methyl ester, did not affect sperm cell motility at 0, 1, 2 or 4 hr, respectively. In contrast, sodium nitroprusside (SNP) significantly inhibited sperm cell motility and caused apoptosis. The adversely dose-dependent effect was only observed if SNP was freshly prepared. Adenosine triphosphate reversed the hazardous effect of SNP on sperm activity/viability. Hemoglobin neutralized the adverse effect of SNP. In hemi-zona sperm fusion test, the number of sperm bound to the zona in the presence of 10(-4) M SNP was significantly less than the control group. SNP at 10(-4) M caused all mouse embryonic development arrest. 46% and 56% of zygote reached the blastocyst stage with the treatment of 10(-6) M and 10(-8) M SNP, respectively, while the control reached 70%. NO adversely affected human sperm activity, human sperm-zona binding and embryonic development. It would appear that high concentration of NO may potentially decrease fertility.