Antioxidants and myocardial contractility: illuminating the "Dark Side" of beta-adrenergic receptor activation?

Oxidant byproducts, such as superoxide anion (O2 ) and hydrogen peroxide, are produced as a consequence of normal aerobic metabolism. These molecules, which are highly reactive with other biological molecules, are referred to as reactive oxygen species (ROS). Under normal physiological conditions, ROS production is balanced by an efficient system of antioxidants, molecules that are capable of scavenging ROS and thereby preventing oxidant damage. At the cellular level, naturally occurring enzymatic antioxidants such as superoxide dismutase, glutathione peroxidase, and catalase play an important role in the conversion of ROS to oxygen and water. Several nonenzymatic antioxidants, including the lipid-soluble antioxidants vitamin E and b-carotene and the water-soluble antioxidants vitamin C and glutathione, are also important in scavenging free radicals. Vitamin C in particular protects plasma lipids from peroxidation, scavenges O2, and plays a role in recycling vitamin E.