Densitometric analysis of β 1 - and β 2 -adrenoceptors in guinea-pig atrioventricular conducting system

P. Molenaar, F. D. Russell, T. Shimada, R. J. Summers

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Abstract

Quantitative autoradiography was used to determine the densities of β 1 - and β 2 -adrenoceptors in the atrioventricular conducting system in guinea-pig. (-)[ 125 I]Cyanopindolol (CYP) was used to label β 1 - and β 2 -adrenoceptors in the absence or presence of the β 1 -adrenoceptor selective antagonist CGP 20712A (100 nm) or the β 2 -adrenoceptor selective antagonist ICI 118,551 (70 nm) or the non-selective β-adrenoceptor antagonist (-)-propranolol (1 μm). Protein in discrete anatomical regions was determined using a densitometric method based on the dye Coomassie brilliant blue G. In the atrioventricular conducting system the proportion of β 2 -adrenoceptors determined by inhibition of total (-)[ 125 I]-CYP binding by CGP 20712A (100 nm) ranged from 32.5% (atrioventricular node) to 48.7% (left bundle branch). In the atrioventricular node (16.8 fmol/mg protein), bundle of His (12.1 fmol/mg protein), right (17.4 fmol/mg protein) and left (21.1 fmol/mg protein) bundle branches and Purkinje cells there was a higher density of β 2 -adrenoceptors than in the interventricular septum (8.4 fmol/mg protein) and right atria (8.3 fmol/mg protein). The medial smooth muscle of the aorta, aortic valve, adventitia of the aorta, nerve tissue, tricuspid and mitral valves contained only β 2 -adrenoceptors. It is speculated that the use of β-adrenoceptor antagonists to control cardiac arrhythmias involving a defect in conduction in the atrioventricular node should take into consideration both β 1 - and β 2 -adrenoceptors.

Original languageEnglish
Pages (from-to)483-495
Number of pages13
JournalJournal of Molecular and Cellular Cardiology
Volume22
Issue number4
DOIs
Publication statusPublished - 1 Jan 1990

Keywords

  • Atrioventricular node
  • Autoradiography
  • Bundle of His
  • CGP 20712A
  • Guinea-pig heart
  • ICI 118,551, (-)[ I]-cyanopindolol
  • Left and right bundle branches
  • Purkinje cells
  • β - and β -adrenoceptors

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