Oxidative stress results when pro-oxidative events predominate in living cells. Such disruption of the normal balance may then originate a chain of injuries to the cell, which can be either reversible or not. This is the case of reperfusion-induced damage to the heart where an increased release of free radicals contributes to the impairment of the organ. In blood vessels, the endothelial cells are very sensitive to oxidative stress, which can induce functional alterations, conducive, in turn, to pathological manifestations, such as high blood pressure, thrombosis and atherosclerosis. A reaction that takes place in all biological membranes is lipoperoxidation. When the rate of this reaction increases, as a result of an abundance of reactive species of free radicals, generalised damage to cell membranes may occur.
To a large extent, the degree of oxidative stress depends on the antioxidative potential of the cell, so when it becomes insufficient, the risk of damage to the cell increases. In this context, enlarging the antioxidant reserves would potentially diminish the chances of cell injury.
Population studies have rendered controversial results about the benefits of antioxidant therapy, either preventive or remedial. The complexity of mechanisms and factors that intervene in oxidative reactions and contribute to their balance, added to individual characteristics of each human subject, make the problem of finding the optimal strategies, a very difficult one.
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