Cellular Compartmentation of Adenosine in the Heart

Summary

The specific activities of adenine nucleotides in coronary endothelial cells in the intact heart by far exceed those obtained in the myocytes. This result illustrates the high activity of the endo-thelium in uptake and incorporation of infused adenosine into the adenine nucleotide pool. However, endothelial cells actively release adenosine. Their relative contribution to the venous adenosine is greater under resting conditions than in the stimulated heart. If at all, the role of the endothelium-derived adenosine to increase coronary blood flow during catecholamines, acetylcholine, and pH reduction seems to be of minor importance. Under these conditions the myocytes are mostly responsible for the changes in the extracellular nucleoside concentrations. The physiologic role of endothelium derived adenosine might be related to a direct interaction with cells in the vascular space, such as thrombocytes and leukocytes.