Effects of superoxide radicals on transport (Na + K) adenosine triphosphatase and protection by superoxide dismutase.

Membrane (Na +K)ATPase isolated from rat brain was preincubated in a medium in which superoxide radicals were generated enzymatically. Exposure to superoxide radicals caused an irreversible inactivation, which could be prevented by further addition of superoxide dismutase. (Na + K)ATPase was also protected by addition of allopurinol, a xanthine oxidase inhibitor, during preincubation. The K-activated nitrophenylphosphatase associated with (Na + K)ATPase was also found to be inactivated by preincubation with superoxide radicals, which could be prevented by superoxide dismutase.