Status of myocardial antioxidants in ischemia-reperfusion injury

Background: Myocardial ischemia-reperfusion represents a clinically relevan t problem associated with thrombolysis, angioplasty and coronary bypass sur gery. Injury of myocardium due to ischemia-reperfusion includes cardiac con tractile dysfunction, arrhythmias as well as irreversible myocyte damage. T hese changes are considered to be the consequence of imbalance between the formation of oxidants and the availability of endogenous antioxidants in th e heart. Observations: An increase in the formation of reactive oxygen spec ies during ischemia-reperfusion and the adverse effects of oxyradicals on m yocardium have now been well established by both direct and indirect measur ements. Although several experimental studies as well as clinical trials ha ve demonstrated the cardioprotective effects of antioxidants, some studies have failed to substantiate the results. Nonetheless, it is becoming eviden t that some of the endogenous antioxidants such as glutathione peroxidase, superoxide dismutase, and catalase act as a primary defense mechanism where as the others including vitamin E may play a secondary role for attenuating the ischemia-reperfusion injury. The importance of various endogenous anti oxidants in suppressing oxidative stress is evident from the depression in their activities and the inhibition of cardiac alterations which they produ ce during ischemia-reperfusion injury. The effects of an antioxidant thiol containing compound, N-acetylcysteine, and ischemic preconditioning were sh own to be similar in preventing changes in the ischemic-reperfused hearts. Conclusions: The available evidence support the role of oxidative stress in ischemia-reperfusion injury and emphasize the importance of antioxidant me chanisms in cardioprotection. (C) 2000 Published by Elsevier Science B.V.