Isoprenaline-induced release of cyclic adenosine 3',5'-monophosphate by the left ventricle in the anaesthetized intact dog.

The ability of the heart to release cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the coronary venous blood was examined in closed-chest anaesthetized dogs before and during an infusion of isoprenaline. Before the infusion, no difference was observed between the cyclic AMP plasma levels in the aortic and coronary sinus blood. During the infusion, significant coronary veno-arterial differences in nucleotide concentration were observed despite a considerable elevation of the cyclic AMP plasma level in the aortic blood.