There is a growing body of evidence to indicate that a significant factor in the aetiology of male infertility involves a loss of sperm function as a consequence of oxidative stress. This stress originates from the excessive generation of reactive oxygen species by the spermatozoa and results in the peroxidation of unsaturated fatty acids in the sperm plasma membrane. It is possible that reactive oxygen species originating from infiltrating leucocytes could also stress the spermatozoa although the protective properties of seminal plasma would render this unlikely in vivo. Whatever the source of the reactive oxygen species, the lipid peroxides thereby generated exhibit powerful negative correlations with the movement characteristics of the spermatozoa and their capacity for sperm-oocyte fusion. These findings should have important implications for the development of rational techniques for the diagnosis and treatment of male infertility.
Male factor accounts for almost 50% cases of infertility. The exact mechanism of sperm dysfunction is not known in many cases. Extensive research in the last decade has led to the identification of free radicals (reactive oxygen species) as mediators of sperm dysfunction in both specific diagnoses and idiopathic cases of male infertility. Elevated levels of reactive oxygen species are seen in up to 30-80% of men with male infertility. The role of free radicals has been studied extensively in the process of human reproduction. We know now that a certain level of free radicals is necessary for normal sperm function, whereas an excessive level of free radicals can cause detrimental effect on sperm function and subsequent fertilisation and offspring health. Oxidative stress develops when there is an imbalance between generation of free radicals and scavenging capacity of anti-oxidants in reproductive tract. Oxidative stress has been shown to affect both standard semen parameters and fertilising capacity. In addition, high levels of free radicals have been associated with lack of or poor fertility outcome after natural conception or assisted reproduction. Diagnostic techniques to quantify free radicals in infertile patients can assist physicians treating patients with infertility to plan for proper treatment strategies. In vivo anti-oxidants can be used against oxidative stress in male reproductive tract. Supplementation of in vitro anti-oxidants can help prevent the oxidative stress during sperm preparation techniques in assisted reproduction.