Effects of endurance training and exercise on tissue antioxidative capacity and acetaminophen detoxification

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Abstract
Both acute acetaminophen toxicity and physical exercise are accompanied by structural and functional damage to tissues. For acute acetaminophen toxicity, this damage occurs mainly in the liver. This damage, which is believed to be initially caused by oxidation and/or arylation, occurs only after depletion of liver glutathione (GSH). GSH normally protects against oxidation and/or arylation. Prolonged physical exercise also depletes GSH in the body. We hypothesized that with endurance training (repeated oxidant stress) tissues will develop mechanisms to prevent GSH depletion. Our results show that, for the same amount of submaximal exercise, trained rats are able to maintain their levels of GSH or their GSH redox status (in the liver, heart, skeletal muscle, and plasma) in contrast to their untrained counterparts. Also, upon administration of acetaminophen, trained rats show a less pronounced depletion in liver GSH than untrained rats. We also hypothesized that training may lead to improved maintenance of tissue GSH homeostasis because of inductions in the enzyme pathways of protection. We observe that training significantly increases (50–70%) glutathione peroxidase and reductase, glucose-6-phosphate dehydrogenase, and catalase activity in heart and skeletal muscle. Since GSH, in addition to providing cellular protection, also functions in other physiological processes including transport and metabolism, the training-induced benefits seen here may have more far-reaching consequences than ever before realized.