BIOCHEMICAL CHANGES OF THE RAT MYOCARDIUM INDUCED BY ISOPROTERENOL

Abstract

The hearts of rats receiving two subcutaneous injections of 40 mg/kg isoproterenol on consecutive days were analyzed 24 hours after the second injection together with those of control rats receiving saline. The myocardial contents of ATP, ADP, AMP, phosphorylcreatine, lactate, and pyruvate were determined enzymatically. Glycogen, creatine, triglyceride, total cholesterol, and phospholipids were also measured.In fed as well as in rats starved for 48 hours, the myocardial ATP and creatine contents were significantly lower in the isoproterenol-treated rats than in the controls. The decrease in ATP level was observed even 48 hours after the last injection. Isoproterenol injections resulted in an increase in pyruvate content and a decrease in triglyceride content of the myocardium of fasted rats. However, the control values of these two substances also differed significantly from those found in fed controls.The total water content of the heart was higher in the isoproterenol-treated fasted rats. The blood content of the myocardium, on the other hand, was decreased in isoproterenol-treated rats.Difficulties involved in proper tissue sampling and handling, together with the importance of the observed changes, are discussed.