Effects of prolonged exercise on oxidative stress and antioxidant defense in endurance horse

Increased oxidative stress during prolonged endurance exercise may end up with muscle damage, fatigue and decreased physical performance. We have recently shown that acute exercise at moderate intensity induced lipid peroxidation, protein oxidation and oxygen radical absorbance capacity (ORAC) in trained trotters. The aim of this study was to measure the changes in oxidative stress and antioxidant defense following an 80-km ride in the blood of endurance horses. Blood samples were collected before and immediately after the ride. Unlike to our previous studies performed on trotters, in endurance horses there were no measurable changes in antioxidants or oxidative stress marker lipid hydroperoxides (LPO) after prolonged exercise. ORAC, vitamin E and lipid hydroperoxide (LPO) concentration or glutathione related enzyme activities were not altered due to the 80-km ride. However, the base line levels of oxidative stress marker were higher in endurance horses compared to trotters. A positive correlation between the pre-ride LPO concentration and erythrocyte glutathione peroxidase (GPx) activity after the ride was observed, which may indicate a protective response of glutathione peroxidase against exercise-induced oxidative stress. Our results suggest that endurance horses have higher oxidative stress levels compared to trotters and a single 80-km ride probably did not suffice to induce oxidative stress and to activate antioxidant defense mechanisms. Key PointsReactive oxygen species (ROS) at lower concentrations have physiological role in the signal transduction and in the regulation of cellular functions. However, the overproduction of ROS results in oxidative stress, an imbalance favoring pro-oxidants over antioxidants.Increased oxidative stress which occurred during prolonged and strenuous physical exercise may end up with muscle damage, fatigue and decreased performance.Prolonged exercise at moderate intensity does not induce oxidative stress in endurance horses.Endurance horses have higher oxidative stress at rest compared to trotters which were trained for short bouts of exercise.