Appearance of adenosine triphosphate in the perfusate from working frog heart.

Frog hearts (Rana pipiens) were perfused in situ with Ringer's solution and the perfusate tested on firefly extract for the presence of ATP. At a normal perfusion pressure of 8 cm. H2O the rate of release of ATP into the perfusate was 8.8 (+/- S.E.1.7) pmoles.min-1. When the workload was increased by raising the perfusion pressure to 12 cm. H2O the rate of release increased to 28.3 (+/- S.E.4.8) pmoles.min-1. The rate of release was found to be proportional to the amount of workload imposed upon the heart. It is postulated that the trigger for release is hypoxia and that the release of ATP from the cardiac cell will augment contractility of the myocardium through its action upon adjacent cells via the P2 purinergic receptor. cells via the P2 purinergic receptor.