The mechanism of K+-induced vasodilation of the coronary vascular bed of the dog.
We tested a number of hypotheses concerning the mechanism of K+-induced vasodilation of the coronary vascular bed. Blood flow in the circumflex artery was measured in pentobarbital-anesthetized, open-chest dogs. Intracircumflex artery bolus injections of 40 mumol of isomotic KCl produced decreases in coronary vascular resistance ranging from 34% to 48%, depending on the initial resistance of the vascular bed. K+ administration had no effect on heart rate and produced a 4 mm Hg decrease in mean arterial pressure. K+ injection caused a 0.2 vol% increase in coronary sinus O2 content in a preparation in which left common coronary flow was held constant. The magnitude of K+-induced vasodilation was not significantly affected by the administration of propranolol, atropine, phentolamine, or lidocaine. K+-induced vasodilation was attenuated (50%) by ouabain plus lidocaine. Acetylcholine-induced vasodilation was not significantly diminished by ouabain plus lidocaine. We conclude that the mechanism of K+-induced vasodilation does not involve an increase in the metabolic activity of the heart or an interaction between K+ and tissue neural elements. Our data do support the hypothesis that K+-induced vasodilation is at least partly the result of an activation of the electrogenic Na+-K+ transport system of coronary smooth muscle.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects* / Q000378:metabolism; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D008012:Lidocaine / Q000494:pharmacology; D009130:Muscle, Smooth / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D010042:Ouabain; D011189:Potassium Chloride; D001285:Atropine; D008012:Lidocaine; D012964:Sodium; D011433:Propranolol; D011188:Potassium; D010646:Phentolamine