LAUSR

BACKGROUND Ischemia-reperfusion (I/R) injury of the heart as a consequence of myocardial infarction or cardiac surgery represents a serious clinical problem. One of the most prominent mechanisms of I/R injury is the development of oxidative stress in the heart. In this regard, I/R has been shown to enhance the production of reactive oxygen/nitrogen species in the heart which lead to the imbalance between the pro-oxidants and antioxidant capacities of the endogenous radical-scavenging systems. OBJECTIVES Increasing the antioxidant capacity of the heart by the administration of exogenous antioxidants is considered beneficial for the heart exposed to I/R. N-acetylcysteine (NAC) and Nmercaptopropionylglycine (MPG) are two sulphur containing amino acid substances, which belong to the broad category of exogenous antioxidants that have been tested for their protective potential in cardiac I/R injury. OBSERVATIONS Pretreatment of hearts with both NAC and MPG has demonstrated that these agents attenuate the I/R-induced alterations in sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils in addition to improving cardiac function. While experimental studies have revealed promising data suggesting beneficial effects of NAC and MPG in cardiac I/R injury, the results of clinical trials are not conclusive because both positive and no effects of these substances have been reported on the post-ischemic recovery of heart following cardiac surgery or myocardial infarction. CONCLUSION It is concluded that both NAC and MPG exert beneficial effects in preventing the I/Rinduced injury; however, further studies are needed to establish their effectiveness in reversing the I/R-induced abnormalities in the heart.