Renal regulation of plasma total antioxidant capacity.

Hyperuricemia has been labeled both a risk factor and marker for cardiovascular pathology in addition to being associated with gout and kidney disease. Uric acid in vitro acts as a potent antioxidant capable of scavenging hydroxy radicals and peroxynitrite and reacting with nitric oxide. Some clinical studies have provided evidence that, in vivo, uric acid is oxidized under conditions associated with high oxidant stress and may spare other antioxidants such as ascorbic acid. The plasma level of uric acid is controlled by the rates of production and excretion or degradation of uric acid. Under most circumstances, it is the renal clearance of uric acid which primarily determines the plasma concentration. Many factors of exogenous and endogenous origin can influence renal tubular absorption and secretion of uric acid. We suggest that renal urate clearance is not haphazard but regulated by an unknown signal that is issued in response to the level of oxidative stress. Since much cardiovascular pathology is now believed to have an inflammatory component and is associated with enhanced production of free radicals, the accompanying hyperuricemia may be viewed as a compensatory response of potential benefit.