Endothelium-dependent coronary vasodilatory action of adenosine : Examination in open-chest dogs

To evaluate the endothelium-dependent coronary vasodilatory effect of adenosine, especially the role of endothelium-derived nitric oxide (EDNO), the dose-response relationship of exogenous adenosine was examined in open-chest dogs before and after intracoronary administration of N(G)-nitro-L-arginine (NNLA), a potent inhibitor of NO synthesis. NNLA attenuated the vasodilatory effect of acetylcholine to less than 25% of the control, which indicates NO synthesis inhibition. NNLA caused a rightward shift of the adenosine dose-response curve with a significant increase of EC(50), whereas there was no significant change in the slope of the regression line calculated by log-logit transformation. These findings suggest that the coronary vasodilatory effect of adenosine is partially induced through an increase of NO release, and this action may play a role in the regulation of coronary vascular tone