Metabolic strategy in mammalian spermatozoa and oxidative stress

Abstract

The ability of sperm to display motion and to propel itself in vivo and in vitro is highly dependent on its capability to produce ATP. Maintenance of sperm motility is not only dependent on the normal function of the contractile proteins of the axoneme and its ability to generate ATP, but also on the availability of metabolic substrate in the female reproductive tract. Metabolic enzymatic activities in sperm have kinetic properties similar to those of muscle cells. Although ATP-utilizing enzymes in these two types of cells are very different at a molecular level, they both produce contractile force. This suggests that sperm's metabolic machinery is designed to produce energy for the contractile work of motility with only minor amounts being consumed in other reactions, including those involved in the process of fertilization. The preferential conversion of glucose to lactate through glycolysis may be an important evolutionary feature of sperm, perhaps intended to minimize the accumulation of reducing equivalents in the mitochondria and subsequent increase in oxygen radical production.