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.
Pelletier
N
N
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824-1314, USA.
Robinson
N E
NE
Kaiser
L
L
Derksen
F J
FJ
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