Spermatozoa experience oxidative, osmotic, chemical, and thermal stresses when cooled, which degrade the quality and fertilizing capacity of the cells. Adding antioxidants to the sperm extender mitigates these alterations. This study evaluated the effect of isoespintanol (ISO) on boar semen subjected to cooling. Fifteen ejaculates from five boars (Sus scrofa domestica) were extended in Beltsville thawing solution (BTS) supplemented with 0 mu M (control), 5 mu M (ISO5), 10 mu M (ISO10), 15 mu M (ISO15), 20 mu M (ISO20), 25 mu M (ISO25), and 30 mu M (ISO30) of ISO, which were then cooled for five days at 16 degrees C. Sperm kinetics, total motility (TM), and progressive motility (PM) were evaluated every 24 h using an IVOS computer-assisted sperm analysis (CASA) system. On day 1 and day 5 of cooling, a hypoosmotic test, spectrofluorometry, and flow cytometry were performed to evaluate the following: membrane functionality, measured as a function of hypoosmotic swelling (HOS); total antioxidant capacity (TAC); reactive oxygen species (ROS); and mitochondrial membrane potential (Delta yen M). Regression analysis and comparison of means using the Duncan test were performed. The ISO added had a slight impact on sperm motility, as evidenced by a reduction in TM at 24 h of cooling (but not prior) with the addition of 20 mu M of ISO. Similarly, no effect of the ISO on the kinetics and functional integrity of the sperm membrane was observed at 96 h of cooling; however, the regression coefficients indicated that the ISO lowered the rate of decrease in sperm motility and the proportion of rapid spermatozoa relative to the concentration of ISO used. The ISO did not affect the TAC of the cooled semen; however, different concentrations of ISO lowered ROS production in the semen after 96 h of cooling. ISO also impacted the Delta yen M of the spermatozoa at 0 h of cooling, increasing the proportion of low Delta yen M cells and decreasing the proportion of high Delta yen M cells. In conclusion, ISO can reduce the loss of quality and oxidative stress occurring in boar semen during cooling and can modulate the mitochondrial activity of sperm.
