Comparative oxidative metabolism in mammalian sperm

In this review, we discuss the physiology of mitochondrial function in sperm using a comparative species approach. Mitochondria impart the ability for sperm from internal fertilizing species to attain individual motility and the ability to navigate the female reproductive tract to the site of fertilization. The presence of reactive oxygen species (ROS) is a normal physiological event of the mitochondrial electron transport chain (ETC); however, when excessive leakage of ROS occurs, sperm damage may follow. ROS production is associated with high levels of sperm motility but must be delicately balanced to prevent cellular damage during post-ejaculatory transport events. We discuss the differences in fundamental oxygen and ATP substrate balance in three mammalian species of veterinary importance, with an emphasis on ETC function, ROS production, and the balance of glycolytic and oxidative phosphorylation production of ATP in sperm.