Tissue responses to hyperoxia. Biochemistry and pathology

An animal model was established to study the toxic effects of hyperoxia and the consequent changes in intracellular antioxidant status. Superoxide dismutase, catalase and glutathione peroxidase activities were measured in erythrocytes, liver and lung, in addition to cellular glutathione concentrations and its associated metabolism. Overt cellular damage was assessed biochemically by measurement of lipid peroxidation, hydrogen peroxide-induced haemolysis and osmotic fragility. Pathological changes were assessed by light and electron microscopy. Up to 11 days exposure of rats to 80% oxygen was not lethal, but resulted in overt cellular damage to red blood cells (haemoglobin concentration decreased from 13.8 +/- 1.4 (SD) g dl-1 to 12.4 +/- 0.5 g dl-1; hydrogen peroxide-induced haemolysis increased from 7.7 +/- 1.6% to 75.1 +/- 13.5% after 11 days of hyperoxia) and to cells of lung (4-fold increase in lipid peroxidation) as well as a biochemical adaptation to the increased concentration of oxygen metabolites (superoxide dismutase increased 3-fold, catalase 5-fold and glutathione peroxidase 2-fold). It is suggested that red cell hydrogen peroxide-induced haemolysis and reduced glutathione concentration may be useful indicators of oxidant stress in the clinical situation.