Coronary Blood Flow and Myocardial Metabolism During Hypoxia in Adrenalectomized-Sympathectomized Dogs

Abstract

The coronary blood flow and carbohydrate metabolism of the heart during hypoxia were studied in two groups of dogs: a) intact animals, and b) those subjected to adrenalectomy and thoracic sympathectomy. The coronary sinus was catheterized via the external jugular vein. The coronary blood flow was measured by the nitrous oxide desaturation technique, and the coronary arteriovenous differences of oxygen, glucose, lactate and pyruvate were determined. A similar increase in coronary blood flow and a comparable change in myocardial carbohydrate metabolism were found during hypoxia in both groups of animals. In the adrenalectomized and partially sympathectomized dogs these changes took place without the increase in heart rate or blood pressure found in the intact animals. It is concluded that the increase in coronary blood flow during hypoxia is not necessarily mediated by either the cardiac sympathetic nerves or the adrenal glands. Local metabolic factors are the primary determinants of coronary blood flow.