REACTIVE OXYGEN SPECIES AND HUMAN SPERMATOZOA - PHYSIOLOGY AND PATHOLOGY

The role of reactive oxygen species (ROS) in the pathophysiology of hu man sperm function has been emphasized in recent years. ROS production in semen has been associated with loss of sperm motility, decreased c apacity for sperm-oocyte fusion and loss of fertility. There is a curr ent presumption that the most prolific source of ROS in sperm suspensi ons is an NADPH oxidase located in leukocytes or in spermatozoa which produces superoxide which is further converted to peroxide by the acti on of superoxide dismutase. Hydrogen peroxide has been recognized as t he most rode oxidizing species for human spermatozoa, which are very s ensitive to lipid peroxidation owing to the high content of polyunsatu rated fatty acids in their plasma membrane, though this is not the sol e mechanism by which sperm function might be impaired by RO. Although the excessive production of ROS is detrimental to human spermatozoa, t here is a growing body of evidence which suggests that ROS are also in volved in the physiological control of some sperm functions. This revi ew focuses on the nature and source oi the ROS generated by human sper mataozoa as well as their operational mechanisms and their effects, wh ich may be detrimental or beneficial.