Release of ATP from Perfused Heart during Coronary Vasodilatation

Abstract

The release of ATP into the coronary circulation during the vasodilatory response to hypoxia of the perfused guinea pig heart has been measured by the highly sensitive firefly luciferin-luciferase assay method. A reduction in perfusion pressure by more than 50% was accompanied by an increase in ATP concentration in the perfusate from 0.21 ± 0.05 to 0.64 ± 0.09 pmol/ml. When ATP (0.1 µM ) was infused into the coronary circulation, about 99% was bound and/or metabolized during transit, indicating that the measured increase in perfusate ATP during hypoxia is likely to be a substantial underestimate of the true release. This conclusion is supported by experiments with the ATPase inhibitor ouabain, which markedly increased the amount of ATP in the perfusate from the hypoxic heart. Neither guanethidine nor hyoscine significantly altered the vasodilatory response to hypoxia, thus indicating that adrenergic and cholinergic nerves are not responsible. Guanethidine and hyoscine also had no effect on the release of ATP. The possibility that ATP is involved in the physiological regulation of coronary flow is discussed, as well as thequestion of whether the source of the ATP is anoxic cardiac muscle or purinergic nerves.