Blockade of putative beta4- and beta1-adrenoceptors by carvedilol in ferret myocardium.
The putative beta4-adrenoceptor mediates positive inotropic effects, action potential shortening and arrhythmias in ferret ventricle. Here we compared the affinity of carvedilol at the putative beta4-adrenoceptor and beta1-adrenoceptor, activated by (+/-)-CGP 12177 and (-)-isoprenaline, respectively. In paced right ventricular preparations, carvedilol (0.01-10 micromol/l) was a simple competitive antagonist of the positive inotropic effects of (+/-)-CGP 12177 (slope of Schild-plot = 1.02, pK(B) = 6.8) and (-)-isoprenaline (slope of Schild-plot = 0.98, pK(B) = 8.1). Carvedilol also blocked putative beta4- and beta1-adrenoceptors of left ventricle, left atrium and sino-atrial pacemaker. Carvedilol therefore interacts with the putative beta4-adrenoceptor according to the law of mass action and may provide a lead in the development of putative beta4-adrenoceptor-selective antagonists.
Lowe
M D
MD
Department of Biochemistry, University of Cambridge, UK.
Grace
A A
AA
Kaumann
A J
AJ
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002227:Carbazoles / Q000494:pharmacology*; D000077261:Carvedilol; D004305:Dose-Response Relationship, Drug; D005289:Ferrets; D006325:Heart Atria / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D011412:Propanolamines / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D012849:Sinoatrial Node / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C120358:adrenergic beta-4 receptor; D000077261:Carvedilol; D007545:Isoproterenol; C033394:CGP 12177