Hydrogen Peroxide in Erythrocytes

Exposure of rats to 5.0 ppm of ozone, and of mice to 6.7 ppm of ozone, for 90 minutes results in a significant decline in erythrocyte catalase levels in animals pretreated with the catalase inhibitor, aminotriazole (ATZ). As ATZ inhibits catalase only after the enzyme has first reacted with hydrogen peroxide, this decline in catalase activity indicates the presence of hydrogen peroxide within erythrocytes during ozone inhalation. Exposure to lower levels of ozone did not produce detectable levels of hydrogen peroxide within erythrocytes. In vitro evaluation of this technique suggests that, as in the human, catalase is not the major enzyme detoxifying hydrogen peroxide in rat erythrocytes. The ATZ-catalase method is therefore limited in its ability to detect the ozone-induced presence of hydrogen peroxide beyond the pulmonary endothelium.