Release of cyclic adenosine 3',5'-monophosphate in the coronary venous blood during an intracoronary infusion of adenosine.

The effect of adenosine on the release of cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the coronary venous blood was examined in 30 anaesthetized intact dogs. Adenosine was infused into the left anterior descending coronary artery (LAD) at a rate of 150 nmol . min-1 and coronary venous blood was sampled in the great cardiac vein (GCV), near the outflow site of the veins accompanying the LAD. Significant coronary veno-arterial differences in cyclic AMP plasma level were observed before and during the infusion. The myocardial blood flow supplied by the LAD increased from 56 +/- 3 to 237 +/- 23 ml . min-1 per 100 g myocardium and the rate of cyclic AMP release in the venous blood near the origin of the GCV increased from 15.2 +/- 3.0 to 104.8 +/- 29.5 pmol . min-1 per 100 g myocardium. The adenosine-induced release of cyclic AMP did not result from an action of the substance on the platelets in the coronary circulation since adenosine concentration comparable to that achieved in the LAD did not modify the cyclic AMP plasma level of arterial blood in vitro. It is concluded that the released nucleotide originated essentially in cardiac structures, i.e. the myocardial and/or coronary cells. The results support in vitro studies suggesting that cyclic AMP is involved in the metabolic regulation of coronary blood flow by adenosine.