Regional differences in endothelial function in horse lungs: possible role in blood flow distribution?
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. Nomega-nitro-L-arginine and NG-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.
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824-1314, USA.
N
N
Pelletier
N E
NE
Robinson
L
L
Kaiser
F J
FJ
Derksen
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006736:Horses / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology; D008168:Lung / Q000502:physiology*; D016210:Methacholine Chloride / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011652:Pulmonary Circulation / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007476:Ionophores; D018721:Muscarinic Agonists; D014665:Vasodilator Agents; D016210:Methacholine Chloride; D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; D000001:Calcimycin; D011189:Potassium Chloride; D019001:Nitric Oxide Synthase; D001920:Bradykinin