Effect of isoproterenol on lipid peroxidation and antioxidant enzymes of myocardial tissue of mice and protection by quinidine.

Administration of isoproterenol to mice at a dose of 30 mg/100 g body weight for 3 consecutive days at an interval of 24 h induced lipid peroxidation in cardiac tissue and exhibited a significantly elevated serum glutamate oxaloacetate transaminase (SGOT) level. Increased superoxide dismutase (SOD) activity with a concomitant decrease in catalase activity has also been observed in cardiac tissue with isoproterenol treatment. Quinidine, a class I antiarrhythmic agent has been found to exhibit a protective role in isoproterenol induced myocardial ischaemia. Cardiac tissue of quinidine treated mice showed reduction of lipid peroxidation reaction. In addition, quinidine treatment is found to influence the cardiac antioxidant enzymes - catalase and SOD. The decrease of SOD activity and increase of catalase activity suggests that quinidine also exerts an 'indirect antioxidant' effect in protecting the myocardial tissue from reactive oxygen species. Furthermore, our current in vitro studies with quinidine have clearly shown in this work that it possesses a very convincing hydroxyl radical scavenging potential with almost no ability to scavenge superoxide anion and hydrogen peroxide (H2O2) in vitro. Thus, our present investigation suggests that quinidine, when administered to mice, strengthens the antioxidant defense system to resist the free radical induced damage brought about by isoproterenol induced ischaemic condition.