Beta-receptor subtypes in the canine coronary circulation.
The principal difficulty in determining the subtype of coronary vascular beta-receptors in vivo is to avoid the local metabolic coronary vasodilation that occurs secondary to activation of myocardial beta-receptors. Therefore, a nonbeating cardiac preparation without chronotropic or inotropic effects is needed. In this study, the coronary circulation was perfused at constant pressure in closed-chest chloralose-anesthetized dogs. The increase in coronary blood flow due to intracoronary injections of the combined beta 1- and beta 2-agonist isoproterenol was determined during prolonged asystoles after the cessation of cardiac pacing in atrioventricular heart-blocked animals. Both beta 1-selective (practolol and L 650,744) and beta 2-selective (ICI 118,551) antagonists blocked isoproterenol-induced coronary vasodilation. In contrast, isoproterenol vasodilation in the femoral circulation was blocked by beta 2- but not by beta 1-selective antagonists. In conclusion, both beta 1- and beta 2-receptors in coronary resistance vessels are stimulated by isoproterenol to produce vasodilation during prolonged asystoles, when cardiac chronotropic and inotropic effects are absent.
Trivella
M G
MG
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
Broten
T P
TP
Feigl
E O
EO
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D003331:Coronary Vessels / Q000502:physiology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000502:physiology; D007269:Injections, Intra-Arterial; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D011217:Practolol / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D007545:Isoproterenol; D011217:Practolol