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N‐nitro l ‐arginine causes coronary vasoconstriction and inhibits endothelium‐dependent vasodilatation in anaesthetized greyhounds
Author(s) -
Woodman O.L.,
Dusting G.J.
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb09802.x
Subject(s) - medicine , vasodilation , vasoconstriction , artery , cardiology , vascular resistance , nitric oxide , constriction , coronary circulation , endothelium , endothelium derived relaxing factor , coronary arteries , nitroarginine , blood flow , coronary vasodilator , anesthesia , blood pressure , nitric oxide synthase
1 The effect of N‐nitro‐ l ‐arginine ( l ‐NNA), an inhibitor of nitric oxide biosynthesis, on large coronary artery diameter and coronary blood flow was examined in anaesthetized greyhounds. The effects of l ‐NNA on the coronary vascular responses to acetylcholine (ACh), glyceryl trinitrate (GTN) and 5‐hydroxytryptamine (5‐HT) were also assessed. 2 l ‐NNA (5 mg kg −1 ), infused into the left circumflex coronary artery, increased systemic mean arterial pressure and decreased the external diameter of the artery. Infusion of l ‐NNA decreased coronary blood flow in 5 of the 7 dogs tested and increased mean coronary resistance but neither of these effects was statistically significant. There was no change in heart rate. 3 Intra‐arterial injection of both ACh (0.01–0.05 μg kg −1 ) and GTN (0.1–0.5μg kg −1 ) increased large coronary artery diameter and coronary blood flow. Coronary vascular responses to the endothelium‐dependent vasodilator ACh were significantly reduced by l ‐NNA, whereas the responses to the endothelium‐independent vasodilator GTN were not significantly affected. 4 5‐HT (0.1 μg kg −1 , injected into the left circumflex coronary artery) decreased coronary artery diameter but increased coronary blood flow. After the administration of l ‐NNA the 5‐HT‐induced dilatation of the coronary resistance vessels was significantly attenuated whereas the constriction of the circumflex coronary artery was increased in 3 out of 3 dogs in which diameter could be measured, although the latter effect was not statistically significant. 5 These data indicate that l ‐NNA causes coronary and systemic vasoconstriction and selectively inhibits endothelium‐dependent vasodilatation in the coronary circulation of the anaesthetized greyhound. Therefore endothelium‐derived NO has an important role in the regulation of coronary vascular tone in the large arteries and the resistance vessels.