The ability of spermatozoa to produce reactive oxygen species (ROS) has been respected since the 1940's. Oxidative stress limits the functional competence of mammalian spermatozoa via lipid peroxidation, the induction of oxidative DNA damage and the formation of protein adducts. Nitric oxide (NO) is a free radical generated from the oxidation of L-arginine to L-citrulline by reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent NO synthases. Several studies suggest that the overproduction of this free radical and the subsequent excessive exposure to oxidative conditions have a potential pathogenetic implication, which due to the reduction of sperm motility. The present study was conducted to study the effect of Zn supplementation on the levels of NO synthase and arginase in semen of patients with asthenozoospmia.

Previous studies suggest that high concentrations of NO play an injurious consequence on spermatozoa kinetic characteristics. These studies reported that NO may react with superoxide or hydrogen peroxide, resulting in the production of peroxinitrite, hydroxyl radical, or singlet oxygen, which cause oxidation of sperm membrane lipids and thiol proteins. NO also may inhibit cellular respiration by nitro-sylation of heme in mitochondrial enzymes, aconitase, and glyceraldehyde phosphate dehydrogenase, leading to a reduction of adenosine triphosphate and that is due to loss of motility of spermatozoa.

Inclusion Criteria:

• the presence of asthenozoospermia in the semen sample.

Exclusion Criteria:

• the absence of endocrinopathy,
• varicocele, and
• female factor infertility. Smokers and alcoholic men were excluded from the study because of their recognized high seminal ROS levels and decreased antioxidant levels

this study includes 60 fertile male partners from couples who had consulted the infertility clinic of babil hospital of maternity (Hilla city/ IRAQ).