The aim of the present study was to investigate the effects of grape seed extract (GSE) on oxidative stress and antioxidant defense markers in acutely and chronically exercised rats.

The study protocol was approved by Ethics Committee of Experimental Medicine Research and Application Center, Selçuk University. Sixty-four adult male Sprague-Dawley rats, weighing 200-300 g at the beginning of the experiment were used. Rats were housed cages with 12/12 h light/dark cycle at 21±2 ^oC and 50 % humidity. Rats were assigned randomly to six groups: Control (C), Control Chronic Exercise (CCE), Control Acute Exercise (CAE), GSE-supplemented Control (GC), GSE-supplemented Chronic Exercise (GCE) and GSE-supplemented Acute Exercise (GAE). Chronic exercise consisted of treadmill running at 25 m.min^-1, 45 min.day^-1, 5 days per week for 6 weeks. Rats in the acute exercise groups were run on the treadmill at 30 m.min^-1 until exhaustion. Rats in the GSE supplemented groups received GSE (100 mg.kg^-1.day^-1) in drinking water for 6 weeks. Rats were sacrificed by cardiac puncture immediately after the exercise in acute exercise groups and 24 h after the last exercise in chronic exercise groups. Control rats were sacrificed under similar conditions. Plasma were separated from the blood for the analysis of malondialdehyde (MDA), xanthine oxidase (XO), adenosine deaminase (ADA), nitric oxide (NO), superoxide dismutase (SOD) and glutathione peroxidase (GPx).

Plasma MDA levels were higher in acute exercise groups and lower in chronic exercise groups compared to the controls. MDA levels were lower in GSE-supplemented groups compared to their controls. XO and ADA activities were higher in CAE group compared to the other groups. Although NO level increased with chronic exercise and with GSE supplementation, it was not different in acute exercise groups compared to the controls. SOD and GPx activities were lower in acute exercise group and higher in chronic exercise group compared to their controls. Antioxidant enzyme activities were higher in GSE-supplemented groups compared to the controls.

We concluded that oxidative stress increases with acute exercise and decreases with chronic exercise and antioxidant enzyme activities decrease with acute exercise and increase with chronic exercise. Oral grape seed extract supplementation prevents exercise-induced oxidative stress by preventing lipid peroxidation and increasing the antioxidant enzyme activities in rats.