Seminal plasma has limited counteracting effects following induction of oxidative stress in donkey spermatozoa

Abstract

The aim of this study was to evaluate the response of donkey spermatozoa to oxidative stress induced by hydrogen peroxide, and to determine whether the presence of seminal plasma modulates the sperm response to that stress. Nine ejaculates were collected, extended in skim milk extender and split into two aliquots. Seminal plasma was removed from the first but not second aliquot. Samples were subsequently split into four aliquots supplemented with different concentrations of commercial hydrogen peroxide (0, 100 and 250µM and 50mM). Aliquots were incubated at 37°C under aerobic conditions and several sperm parameters, namely motility, viability, intracellular levels of peroxides and superoxides and mitochondrial membrane potential, were evaluated at 0, 1 and 3h. Exposure to hydrogen peroxide markedly decreased sperm motility but had much less of an effect on sperm viability, mitochondrial membrane potential and intracellular reactive oxygen species levels. A protective effect of seminal plasma against the loss of sperm motility was not apparent, but some kinetic parameters and relative levels of superoxides were better maintained when seminal plasma was present together with high concentration of hydrogen peroxide. In conclusion, oxidative stress induced by hydrogen peroxide reduces donkey sperm motility and has a less apparent effect on other sperm parameters. Finally, seminal plasma is only able to partially ameliorate the detrimental effect of this induced stress.