Comparative relaxant effects of nitroglycerin in isolated rings from various canine vascular beds

1. 1. The potency of nitroglycerin to block contractions produced by norepinephrine, serotonin and KCl, was examined in isolated large artery rings obtained from the coronary, femoral, mesenteric and renal vascular bed of the dog. 2. 2. Nitroglycerin was a more potent antagonist (10–10,000 fold) of contractions produced by norepinephrine in the large coronary artery than in the other three vascular beds. 3. 3. Similarly, nitroglycerin blocked responses to serotonin and KCl (40 mM) more effectively in the coronary vs the femoral artery. 4. 4. These results suggest that nitroglycerin has selectivity for the large coronary artery of the dog in blocking contractions produced by three constrictor substances that have been implicated in coronary vasospasm.