Mitochondrial OXPHOS is involved in the protective effects of L-arginine against heat-induced low sperm motility of boar

The present study aimed to analyze the time- and temperature-responses of boar sperm and clarify the mechanism underlying the protective effects of L-arginine on heat-induced low sperm motility. Mature boar sperm was used to evaluate the effects of temperature, exposure time, L-arginine level and their interactions on sperm motility, respectively. Results showed increasing exposure time resulted in the decreased total motility and rate of rapid progressive sperm, and the increased rates of the immotile sperm and the sperm shaking in place at 38 and 39 °C, respectively (P < 0.05). L-arginine supplementation at the dose of 1.0 mM increased total motility and decreased rate of immotile sperm (P < 0.05). Heat at 39 °C decreased total motile and rate of rapid progressive sperm (P < 0.05), increased the level of sperm reactive oxygen species (ROS) (P < 0.05), reduced mitochondrial membrane potential (ΔΨm), ATP content and the activities of mitochondrial respiratory chain complexes (MRCC) ΙΙΙ and V (P < 0.05), which were attenuated by L-arginine supplementation. There were significant increases in the relative mRNA expression of nuclear respiratory factor 1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha in heat-exposed group without L-arginine supplementation. In conclusion, the rising temperatures impacted boar sperm motility in a time-dependent manner. In vitro addition of L-arginine to boar semen had a dose-dependent effect on sperm motility and sperm incubated with 1.0 mM L-arginine showed elevated motility. L-arginine supplementation can ameliorate heat-induced increase in ROS level and decreases in MRCC activities, which further maintain mitochondrial oxidative phosphorylation function, ATP synthesis and boar sperm motility.