β‐Adrenoceptors of the human myocardium: determination of β1 and β2 subtypes by radioligand binding

Abstract

β‐Adrenoceptors of the human myocardium were investigated with binding studies using ¹²⁵iodocyanopindolol (ICYP) as ligand. Inhibition of ICYP‐binding by betaxolol (a selective β₁‐antagonist) and ICI 118551 (a selective β₂‐blocking drug) resulted in non‐linear Scatchard‐plots suggesting that both β‐adrenoceptor subtypes are present in human left atrium and left ventricle. Computer analysis of the data gave a β₁/β₂‐adrenoceptor ratio of approximately 65:35 both for left atrium and for left ventricle.