Action of uric acid, allopurinol and oxypurinol on the myeloperoxidase-derived oxidant hypochlorous acid.

Both oxypurinol and uric acid react with the myeloperoxidase-derived oxidant hypochlorous acid at physiological pH, and they can protect the elastase-inhibitory capacity of human alpha 1-antiprotease against inactivation by hypochlorous acid. Allopurinol does not protect alpha 1-antiprotease, possibly because the redox potential of allopurinol at physiological pH is too positive to permit oxidation by hypochlorous acid.