Binding characteristics of ( )-, (±)- and (-)-[125Iodo] cyanopindolol to guinea-pig left ventricle membranes

Abstract

[125Iodo]cyanopindolol [(±)-ICYP], a potent and selective ligand for β-adrenoceptors, exhibited complex biphasic dissociation kinetics. Consequently, in receptor binding studies, the pure (+)- and (-)-enantiomers of ICYP were synthesised and their equilibrium and kinetic binding characteristics were investigated on a membrane preparation of guinea pig left ventricle containing almost only β1-adrenoceptors. All three ligands, i. e. (+)-, (-)- and (±)-ICYP, bind to β-adrenoceptors as assessed by competition experiments with different β-blocking agents; irrespective of the ligand used, the same dissociation constant was found for the competitor. In a first series of saturation binding experimen..