Studies on the hexose monophosphate shunt in the myocardium during development of hypertrophy

In rat hearts hypertrophying because of aortic constriction and isoproterenol administration, the activity of glucose-6-phosphate dehydrogenase and the available pool of 5-phosphoribosyl-l-pyrophosphate were found to be increased, indicating an enhancement of the flow through the hexose monophosphate shunt. In triiodothyronine-treated animals only the cardiac pool of 5-phosphoribosyl-l-pyrophosphate was elevated. In all three models of experimentally induced cardiac hypertrophy, the enhancement of myocardial adenine nucleotide biosynthesis was potentiated by ribose. Since ribose gives rise to a considerable elevation of the available 5-phosphoribosyl-l-pyrophosphate, it appears that this is the limiting factor for the increase of adenine nucleotide biosynthesis in hypertrophying hearts. Constant intravenous infusion of ribose for 24 hr prevented the decrease of myocardial ATP concentration is isoproterenol-treated rats.