title: Autoradiographic localization and quantitation of beta 1- and beta 2-adrenoceptors in the human atrioventricular conducting system: a comparison of patients with idiopathic dilated cardiomyopathy and ischemic heart disease.
abstract: The density and distribution of beta 1- and beta 2-adrenoceptors in the atrioventricular conducting system and interatrial and interventricular septa from human hearts with idiopathic dilated cardiomyopathy and ischemic heart disease was determined by quantitative autoradiography using (-)[125I]cyanopindolol and the selective beta 1-adrenoceptor antagonist CGP 20712A and the selective beta 2-adrenoceptor antagonist ICI 118,551. Both beta 1- and beta 2-adrenoceptors were present in the atrioventricular node, bundle of His, interatrial and interventricular septa. No differences in the density or proportions of beta 1- and beta 2-adrenoceptors in the atrioventricular node, bundle of His, interatrial septum and interventricular septum were observed between hearts with idiopathic dilated cardiomyopathy or ischemic heart disease (P > 0.05) so further analysis did not distinguish between the two aetiologies. The density of beta 1-adrenoceptors was lower in the bundle of His (5.0 +/- 1.7 fmol/mg protein) than in the atrioventricular node (22.2 +/- 5.7 fmol/mg protein, P < 0.05), the interatrial septum (29.6 +/- 4.5 fmol/mg protein, P < 0.001) and interventricular septum (24.9 +/- 5.2 fmol/mg protein, P < 0.005, n = 8 for all values). The atrioventricular node, interatrial and interventricular septa had similar densities of beta 1-adrenoceptors (P = 0.60, ANOVA). The distribution of beta 2-adrenoceptors in the atrioventricular node (21.5 +/- 4.1 fmol/mg protein), bundle of His (12.9 +/- 2.6 fmol/mg protein) and atrial (16.7 +/- 2.3 fmol/mg protein) and septal myocardium (13.8 +/- 2.5 fmol/mg protein, n = 8 for all values) was uniform (P = 0.18, ANOVA). The percentage of beta 1- and beta 2-adrenoceptors in the atrioventricular node, bundle of His, interatrial and interventricular septa was uneven (P < 0.001, ANOVA). There was a higher proportion of beta 2-adrenoceptors in the bundle of His (72 +/- 6%) than in the atrioventricular node (51 +/- 3%, P < 0.01), interatrial septum (36 +/- 1%, P < 0.001) and interventricular septum (36 +/- 1%, P < 0.001).
authors.affiliation: Department of Pharmacology, University of Melbourne, Parkville Vic., Australia.
authors.forename: J
authors.initials: J
authors.lastname: Elnatan
authors.forename: P
authors.initials: P
authors.lastname: Molenaar
authors.forename: F L
authors.initials: FL
authors.lastname: Rosenfeldt
authors.forename: R J
authors.initials: RJ
authors.lastname: Summers
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000378:metabolism* / Q000494:pharmacology; D000328:Adult; D000368:Aged; D001283:Atrioventricular Node / Q000737:chemistry*; D001667:Binding, Competitive; D002036:Bundle of His / Q000737:chemistry; D002311:Cardiomyopathy, Dilated / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D006346:Heart Septum / Q000737:chemistry; D006801:Humans; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000032:analysis* / Q000145:classification; D017202:Myocardial Ischemia / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives* / Q000378:metabolism; D011412:Propanolamines / Q000378:metabolism / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000032:analysis* / Q000145:classification / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D007093:Imidazoles; D009124:Muscle Proteins; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; C047975:cyanopindolol; D010869:Pindolol; C049763:CGP 20712A