Role of Uric Acid as an Endogenous Radical Scavenger and Antioxidant

¹ The Department of Physiology, University of Munich, Munich, Germany.
² The Medical Clinic I, Technical University of Munich, Munich, Germany.

Because uric acid is present in high concentrations in plasma and seems particularly efficient at inactivating 2 very powerful oxidants, HO and HOCl, this substance can be assumed to act as a potent scavenger in vivo. Together with the other known scavenger systems, a protective screen against oxygen radicals and oxidants is therefore established under normal conditions. Since the scavengers are never totally suppressed or absent, the involvement of radicals in pathologic processes is difficult to prove. Likewise, a deficiency in any one scavenger type may be quite well tolerated by the living organism.

Finally, a net release of uric acid is observed from the heart and lung of man when under treatment with anti-inflammatory drugs (the subjects with heart transplants were also receiving corticosteroids). Whether uric acid serves to protect the coronary and pulmonary vascular systems in man from functional damage by oxidants such as HOCl remains to be explicitly proven. In the human lung tissue, however, we have evidence that uric acid is involved in antioxidant reactions.