EFFECT OF ALPHA -TOCOPHEROL ON ISOPROTERENOL-INDUCED CHANGES IN LIPID AND LIPOPROTEIN PROFILE IN RATS

Objectives: To find the effect of a-tocopherol pretreatment on the lipid and lipoprotein profile after administration of isoproterenol in the doses which have been demonstrated to induce myocardial infarction in rats. Methods: The effect of a-tocopherol (6mg/100 g for a period of 90 days) pretreatment on isoproterenol (20mg/ 100g s.c., twice at an interval of 24h) induced changes in lipid and lipoprotein profile was studied in rats. Serum lipoproteins were separated by a dual precipitation method and cholesterol and triglycerides were estimated using standard established procedures. Lipid peroxides, lipoprotein lipase, triglyceride lipase, cholesterol ester synthetase and cholesterol ester hydrolase activities were estimated in heart homogenate. Total cholesterol, free cholesterol, triglycerides, phospholipid and free fatty acids were estimated in serum and heart. Results: A significant increase was observed in the levels of total cholesterol, ester cholesterol, triglycerides and free fatty acids in serum and heart of isoproterenol treated rats. The myocardial phospholipid content decreased significantly on isoproterenol administration. lsoproterenol administered rats showed a significant decrease in the activity of cholesterol ester hydrolase and lipoprotein lipase, whereas cholesterol ester synthetase and triglyceride lipase activity was observed to be increased. In isoproterenol administered rats, cholesterol and triglycerides in LDL and VLDL fractions increased significantly with a significant decrease in the HDL fraction. In rats pretreated with a-tocopherol, the alterations observed in the lipids, lipid metabolising enzymes and serum lipoproteins were minimum on isoproterenol administration, and the levels were retained at near normal values. Conclusion: The results obtained in the present study indicates that a-tocopherol pretreatment offers protection in experimental myocardial infarction induced by isoproterenol, by preventing lipid peroxidation and overloading of myocardium with lipids thus maintaining the structure and function of the myocardium.