Regional differences in endothelial function in horse lungs: possible role in blood flow distribution?

• Published in: Journal of applied physiology (1985) 1998-08, Vol.85 (2), p.537-542
• Main Authors: Pelletier, Nicolas, Robinson, N. Edward, Kaiser, Lana, Derksen, Frederik J
• Format: Article
• Language: English
• Subjects: Air breathing; Anatomy & physiology; Animals; Biological and medical sciences; Blood vessels; Bradykinin - pharmacology; Calcimycin - pharmacology; Endothelium, Vascular - physiology; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Horses; Horses - physiology; Ionophores - pharmacology; Lung - physiology; Lungs; Methacholine Chloride - pharmacology; Muscarinic Agonists - pharmacology; Nitric Oxide - biosynthesis; Nitric Oxide - physiology; Nitric Oxide Synthase - antagonists & inhibitors; Nitroarginine - pharmacology; Nitroprusside - pharmacology; Potassium Chloride - pharmacology; Pulmonary Circulation - physiology; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Space life sciences; Vasodilation - drug effects; Vasodilator Agents - pharmacology; Vertebrates: respiratory system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.85.2.537

Departments of Large Animal Clinical Sciences and Physiology, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824-1314 We investigated regional differences of in vitro responses of pulmonary arteries (6-mm OD) from the dorsocaudal (top) and cranioventral (bottom) lung regions to endothelium-dependent vasodilators (methacholine, bradykinin, and calcium ionophore A-23187). Methacholine relaxed endothelium-intact top vessels; however, in bottom vessels, a small relaxation preceded a profound contraction. In top vessels, removal of endothelial cells converted relaxation to contraction, and in bottom vessels it abolished relaxation and enhanced contraction. Bradykinin and A-23187 were more potent and caused greater endothelium-mediated relaxation in top than in bottom arteries. The endothelium-independent vasodilator sodium nitroprusside caused similar relaxations in all rings. N -nitro- L -arginine and N G -monomethyl- L -arginine and methylene blue abolished relaxation of top and bottom arteries to methacholine; meclofenamate had little effect. We conclude that regional differences in endothelium-mediated relaxation are caused by differences in the magnitude of the endothelial release of nitric oxide. Similar differences in endothelium-dependent flow-mediated vasodilation and endothelial nitric oxide release may result in preferential perfusion of caudodorsal lung regions. endothelium; endothelium-dependent relaxation; nitric oxide; distribution of pulmonary blood flow; regional perfusion