Antioxidant systems and oxidative stress in the testes

Spermatogenesis is an extremely active replicative process capable of generating approximately 1,000 sperm a second. The high rates of cell division inherent in this proccss simply correspondingly high rates of mitochondrial oxygen consumption by the germinal epirheliun. However, the poor vascularizarion of the testes means that oxygen tensions in this tissue are low and that competition for this vital element within the testes is extremely intense. Since both spermatogenesis and Leydig cell steroidogenesis are vunerable to oxidative stress, the low oxygen tension that characterizes this tissue may be an important component of the mechanisms by which the testes protects itself from free radical-mediated damage. In addition, the testes contain an elaborate array of antioxidant enzymes and free radical scavengers to ensure that the twin spermatogenic and steroidogenic functions of this organare are not impacted by oxidative stress. These antioxidant defence systems are of major importance because peroxidative damage is currently regarded as the single most important cause of imnpaired testicular function underpinning the pathological consequences of a wide range of conditions from testicular torsion to diabetes and xenobiotic exposure. This chapter sets out the specific nature of these antioxidant defence systems and also reviews the factors that have been found to impair their activity, precipitating a state of oxidative stress in the testes and impairing thetlatter's ability to produce viable spermatozoa capable of initiating and supporting embryonic development