CAT and myocardial infarction: The CK-MB is present in a relatively high concentration in the myocardium and its activity is a useful index for diagnosis of myocardial infarction.33 Increase in MDA contents, the oxidative stress marker, and decrease in antioxidant enzymes (SOD and catalase) activity produced by isoproterenol may be due to increased reactive oxygen species (ROS) generation.7 The MDA is a reliable and common biomarker for assessing lipid peroxidation.