Studies on myocardial metabolism in the ischemic heart. 1. Studies on ammonia metabolism

Abstract

There have been many experimental reports of metabolic and physiological changes in the heart muscle under various ischemic conditions, however, very few studies are available on ammonia metabolism in the ischemic myocardium. The purpose of this paper is to clarify the myocardial metabolism in the ischemic heart with special reference to ammonia and its related substances. Method : Twenty four adult mongrel dogs were used Myocardial ischemia was produced by inserting fluoroscopically a Cournand catheter into the left coronary artery through the left carotid artery. By means of the special coronary sinus catheterization technique, the coronary A-V differences were measured on the concentrations of ammonia, urea, glutamine, amino acids, lactate, pyruvate and α-ceketoglutarate. Oxygen content and pH in coronary arterial and sinus blood were also measured. Coronary blood flow, systemic blood pressure and ECG were recorded with simultaneous blood sampling at three points: before the ischemic condition (control), 5 minutes after the insertion of a catheter into the coronary artery (during ischemia) and 10 minutes after the withdrawal of the catheter (recovery). Myocardial contents of high energy phosphates (ATP, ADP and AMP), inorganic phosphorus, and ammonia were also estimated 5 minutes after the insertion of the catheter. Result and Discussion Hemodynamic and ECG changes occurred immediately after the coronary artery catheterization. Decreases in arterial systolic pressure, coronary flow and pulse rate were observed during ischemia. ST-T changes were variable. After the withdrawal of the catheter coronary flow and pulse rate recovered and even increased, though blood pressure and ST-T changes had no significant recovery. Myocardial external work showed a significant decrease during ischemia. In some cases cardiac arrest was observed. Under the rschemic condition, myocardial (apical portion) ammonia content increased significantly. Coronary A-V differences of ammonia and glutamine inclined to release during ischemia. A significant correlation between the changes in the coronary A-V differences of ammonia and glutamine was found (γ=-0.754). There were little changes in urea and arginine content of arterial or coronary sinus blood. Coronary A-V differences of glutamic acid and alanine inclined to take-up during ischemia.