POSSIBLE ROLE OF NITRIC-OXIDE ON FERTILE AND ASTHENOZOOSPERMIC INFERTILE HUMAN SPERM FUNCTIONS

The capacity of human sperm fertilization is principally dependent on sperm motility and membrane integrity. Oxygen-derived free radicals, s uch as superoxide anion, are known to impair sperm motility and membra ne integrity by inducing membrane Lipid peroxidation (LPO). Nitric oxi de (NO), a biologically active free radical, has recently been shown t o inactivate superoxide and increase intracellular guanosine-3', 5'-cy clic monophosphate (cGMP). The aim of this study is to investigate the effects of NO on human sperm motility, viability, lipid peroxidation and cGMP in fertile and asthenozoospermic infertile individuals in vit ro. Semen samples were obtained from 10 fertile volunteers and 10 asth enozoospermic infertile patients. Washed spermatozoa were incubated at 37 degrees C in Ham's F-10 medium with 0, 25, 50, 100, 200, or 400nM sodium nitroprusside (SNP, Na-2 [Fe(CN) 5NO] 2H(2)O), a nitric oxide r eleaser. Samples were analyzed for viability, determined by eosin-Y dy e exclusion method at 0, 1, 2, 3, 5 and 6 h of incubation; motility, d etermined by the trans-membrane migration method within 2 h of incubat ion; LPO determined by malondialdehyde (MDA) -thiobarbituric acid meth od at 3 h of incubation; and the intracellular cGMP, determined by I-1 25-cGMP radioimmunoassay at 3 h of incubation. The results showed: in both fertile and infertile samples, viability, trans-membrane migratio n ratio and the levels of intracellular cGMP in 25-100nM SNP-treated s permatozoa were significantly higher than those in control groups, whi le MDA contents in treated groups were significantly lower than those in controls. However, when concentrations of SNP increased to 200-400n M, the opposite effects were exhibited. The effects of SNP on these pr ocesses were biphasic within 25-400nM. The most effective concentratio n was 100nM. These data suggested that NO is beneficial to sperm viabi lity and motility in both fertile and infertile individuals, and that reduction of lipid peroxidative damage to sperm membranes and increase of intracellular cGMP may be involved in these benefits.