Superoxide, superoxide dismutase and the respiratory burst.
Phagocytes undergo a sharp burst of oxygen consumption when engulfing bacteria. This oxygen is enzymatically reduced to toxic metabolites which are essential to the bactericidal action of the cell. Oxygen metabolites formed in this burst as well as other intermediates formed in biological reduction reactions do not selectively reserve their toxicity for microorganisms. Cells help to guard their organelles against the toxic effects of oxygen by producing intracellular enzymes such as superoxide dismutase. Though superoxide dismutase is found in relatively high concentrations inside cells, there are only small amounts in extracellular fluids. This may account for some of the local tissue damage surrounding aggregates of neutrophils in inflammatory reactions. A pharmacological preparation of superoxide dismutase has shown efficacy in preventing some of the pathological changes seen in degenerative arthritis.
Divisions of Veterinary Biology and Clinical Studies and Pathobiology and Public Practice, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
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