Mitochondrial ATP is required for the maintenance of membrane integrity in stallion spermatozoa, whereas motility requires both glycolysis and oxidative phosphorylation

Abstract

To investigate the hypothesis that oxidative phosphorylation is a major source of ATP to fuel stallion sperm motility, oxidative phosphorylation was suppressed using the mitochondrial uncouplers CCCP and 2,4,-dinitrophenol (DNP) and by inhibiting mitochondrial respiration at complex IV using sodium cyanide or at the level of ATP synthase using oligomycin-A. As mitochondrial dysfunction may also lead to oxidative stress, production of reactive oxygen species was monitored simultaneously. All inhibitors reduced ATP content, but oligomycin-A did so most profoundly. Oligomycin-A and CCCP also significantly reduced mitochondrial membrane potential. Sperm motility almost completely ceased after the inhibition of mitochondrial respiration and both percentage of motile sperm and sperm velocity were reduced in the presence of mitochondrial uncouplers. Inhibition of ATP synthesis resulted in the loss of sperm membrane integrity and increased the production of reactive oxygen species by degenerating sperm. Inhibition of glycolysis by deoxyglucose led to reduced sperm velocities and reduced ATP content, but not to loss of membrane integrity. These results suggest that, in contrast to many other mammalian species, stallion spermatozoa rely primarily on oxidative phosphorylation to generate the energy required for instance to maintain a functional Na/K gradient, which is dependent on an Na-K antiporter ATPase, which relates directly to the noted membrane integrity loss. Under aerobic conditions, however, glycolysis also provides the energy required for sperm motility.

UCP2 Mitigates the Loss of Human Spermatozoa Motility by Promoting mROS Elimination

“…Hence, the content of mROS is positively correlated with the levels of ATP and MMP. A positive correlation between mitochondrial energy function and spermatozoa motility has been demonstrated [14,26,35,36]. In these studies, it was found that the levels of MMP and ATP are significantly higher in the NS group than in the AS group, but the mROS levels show a reverse trend, implying that one special mechanism exists in the NS group to either inhibit mROS production or promote mROS elimination.…”

A New Method for Evaluating Stallion Sperm Viability and Mitochondrial Membrane Potential in Fixed Semen Samples

“…Sperm membrane integrity is one of the key assays in stallion sperm evaluation (24). Mitochondria are key structures of the spermatozoa (15,26), and appear especially important in stallion spermatozoa, due to a higher dependence of oxidative phosphorylation in this species (12,27,28). Mitochondria are key structures of the spermatozoa (15,26), and appear especially important in stallion spermatozoa, due to a higher dependence of oxidative phosphorylation in this species (12,27,28).…”

The Stimulated Glycolytic Pathway Is Able to Maintain ATP Levels and Kinetic Patterns of Bovine Epididymal Sperm Subjected to Mitochondrial Uncoupling

“…Davila et al [8] demonstrated that equine spermatozoa require oxidative phosphorylation as glycolytic pathway to maintain motility. Complementary in ram, Losano et al [9] demonstrated that mitochondrial depolarization did not affect total motility; however, sperm kinetic patterns were altered.…”