Cardiac nucleotides in hypoxia: possible role in regulation of coronary blood flow

Experiments were performed on isolated cat hearts perfused with Tyrode's solution and intact hearts of open-chest dogs. Cardiac hypoxia resulted in a decrease in coronary vascular resistance and a release of significant amounts of inosine and hypoxanthine from the myocardium. From 3 to 27 times more inosine and hypoxanthine were released from the heart during myocardial hypoxia than were required to double the coronary blood flow when infused as adenosine into the left coronary artery. Based on the assumption that with hypoxia the nucleotide derivatives leave the myocardial cell as adenosine, an hypothesis is proposed for the metabolic regulation of coronary blood flow.