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Relaxant responses to vasodilators, including nitroglycerin, sodium nitroprusside, prostaglandin I2 sodium salt (PGI2), prostaglandin E1 (PGE1), diltiazem hydrochloride and adenosine, were compared in helical strips of dog coronary arteries of different sizes and in coronary and mesenteric arterial strips. The relaxant responses to nitroglycerin, sodium nitroprusside, diltiazem and adenosine were significantly greater in coronary arteries than in mesenteric arteries, whereas the responses to PGI2 and PGE1 in these arteries did not significantly differ. In coronary arteries of different sizes, the relaxation induced by nitroglycerin was in the order of large greater than medium greater than small-size, while in contrast, the relaxations by adenosine, PGI2 and PGE1 were greatest in the small-size arteries and least in the large-size arteries. The relaxant responses to sodium nitroprusside and diltiazem did not differ in the coronary arteries of different sizes. Nitroglycerin, sodium nitroprusside and diltiazem appear to dilate coronary arteries more predominantly than mesenteric arteries. The preferential dilator action of PGI2 and PGE1 on distal coronary arteries, like that of adenosine, may lead more blood to re-distribute to the non-ischemic region of the heart in anginal patients.
Miwa et al. (Tue,) studied this question.