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
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.