Nitric oxide (NO) is a signaling molecule produced by intracellular nitric oxide synthase (NOS) enzymes.
Studies have shown that this free radical affect sperm capacitation, a maturation step preceding acrosome reaction. This
study was aimed at investigating the effects of exogenously administered NO through its donor, sodium nitroprusside
(SNP) has on human sperm motility, viability and apoptosis markers. Increased concentrations of SNP (10, 30, 50,
100 M) were administered to human spermatozoa in the presence or absence of NO synthase inhibitor, N-nitro-Larginine
methyl ester. Spermatozoa motility and viability were assessed at 60 and 90 minutes of incubation. The caspase
activity was assessed after 90 minutes of incubation. SNP significantly decreased spermatozoa motility and viability in a
dose and time dependent manner (p < 0.05). The caspase activity was significantly increased with increasing
concentration of SNP (p < 0.05). This study therefore conclude that high concentrations of NO result in the decrease of
sperm function and increase of germ cell apoptosis rate that may contribute to male infertility.