Studies on the Enzymes of Urea Cycle Intermediates in Normal and Infarcted Myocardial Tissue of Rat
The high content of glutamine and the high activity of aspartic acid aminotransferase signifies that myocardium has an appreciable amount of nitrogenous metabolism. It is well established that in extra hepatic tissues the ammonia is mainly disposed of in the form of glutamine. It has been demonstrated by Russian workers that the urea content in coronary sinus blood was high in patients suffering from varying degrees of myocardial infarction. A study of three enzymes belonging to urea cycle, namely, argininosuccinate synthetase, argininosuccinase and arginase has been made in the myocardium of normal rats and in rats subjected to myocardial infarction. It was observed that the myocardial tissue did not exhibit any activity of argininosuccinate synthetase while appreciable activity of argininosuccinase and arginase was observed. The arginase activity was significantly higher in the left side of the heart than in the right side. The activity of this enzyme was found to be 1 1/2 times more in the infarcted tissue. Though the argininosuccinase activity was almost the same in both sides of the heart it was, however, found to be higher in the infarcted tissue. A similar difference in the activity of ornithine aminotransferase was found between the left and right sides of the myocardium and the infarcted tissue appears to have a significant metabolism of arginine. Its enhancement in infarcted tissue together with increased activity of ornithine aminotransferase may help in the production of glutamate and in the removal of ammonia.