EFFECT OF TRAINING ON ANTIOXIDANT CAPACITY, TISSUE-DAMAGE, AND ENDURANCE OF ADULT MALE RATS

We studied the effects of physical training on antioxidant defences an d susceptibility to damage induced by exhaustive exercise in tissues o f adult (12 mo) rats. Therefore, untrained animals were sacrificed eit her at rest (n=8) or immediately after swimming to exhaustion (n=8). R ats trained to swim for 10 weeks were also sacrificed, 48 hr after the last exercise, either at rest (n=8) or after exhaustive swimming (n=8 ). integrity of mitochondria and sarcoplasmic (SR) or endoplasmic (ER) reticulum of liver, heart, and muscle was assessed by measuring mitoc hondria respiratory control and latency of alkaline phosphatase activi ty. Lipid peroxidation was measured by determination of malondialdehyd e and hydroperoxides. Additionally, the effect of training on tissue a ntioxidant systems was examined by determining the glutathione peroxid ase (GPX) and glutathione reductase (GR) activity and the overall anti oxidant capacity (C-A) Membrane integrity was unaffected by training i n liver and muscle, and improved in heart of at rest animals, whereas lipid peroxidation was reduced in both liver and heart. Glutathione pe roxidase and glutathione reductase activity, and overall antioxidant c apacity were increased (p<0.05) by training in liver and muscle. In he art, antioxidant capacity was increased from 0.21+/-0.01 to 0.33+/-0.0 2 (p<0.05), but glutathione peroxidase activity remained unchanged (p> 0.05), and glutathione reductase activity was decreased from 3.56+/-0. 08 to 2.27+/-0.10 mu mol x min(-1) x g(-1) (p<0.05). The exhaustive ex ercise gave rise to tissue damage irrespective of trained state, as do cumented by similar loss of SR and ER integrity, and increase (p<0.05) in lipid peroxidation found in exhausted trained and untrained rats. However, the above changes were elicited by exercise of greater durati on in trained than in untrained rats (340+/-17 min and 233+/-6 min, re spectively). These findings support the view that free radical-induced damage in muscle could be one of the factors involved in muscle fatig ue. if so, the increased endurance in trained rats should reflect leng thening of the time required for the oxidative processes to sufficient ly impair cell functions so as to make further exercise impossible.