MYOCARDIAL METABOLISM IN STARVED AND HYPOPROTEINEMIC DOGS

Abstract

The myocardial metabolism in dogs during starvation and during hypoproteinemia produced by plasmapheresis have been investigated, using the coronary sinus catheterization. In addition, the effects of glucose, mixed amino acid preparation, and cardiac glycosides on them have been observed. Following results were obtained. 1) After about a week of fast, the myocardial extraction of carbohydrates was markedly decreased (in some cases, the coronary arteriovenous differences of glucose, lactate, and pyruvate were negative) and that of fats was increased, accompanied by depression of the myocardial respiratory quotient. The myocardial extractions of oxygen and amino acids were scarcely altered. Cardiac function was generally depressed. During starvation, fat comes to main fuel in the heart instead of carbohydrate as in the other organs. 2) When dogs in the above condition were given 50 per cent glucose, the myocardial extraction of carbohydrates was markedly increased with the abnormally marked elevation of the arterial levels, that of fats and amino acids decreased, that of oxygen increased, and the myocardial respiratory quotient elevated. Following the administration of mixed amino acid peparation, the myocardial metabolism showed a tendency to return to the normal state, but the effect of it was inferior to that of glucose. Following the administration of digitoxin, there was no obvious change in cardiac metabolism and function. Following the administration of strophanthin, the myocardial metabolism was altered little, but the cardiac function was somewhat recovered. 3) In dogs with hypoproteinemia, changes in cardiac metabolism and function showed the same tendencies as in starved dogs, except for decrease of oxygen extraction. During hypoproteinemia, the heart derives its energy from fat mainly as during starvation. 4) When dogs in the above condition were given 50 per cent glucose, the myocardial metabolism showed a tendency to return to the normal state. After mixed amino acid preparation, the myocardial extractions of oxygen and carbohydrates were considerably increased, that of fats decreased, the myocardial respiratory quotient elevated, and thus the myocardial metabolism recovered remarkably. Concerning cardiac glycosides, the same results were obtained as in starved dogs.