[125Iodo]BE 2254, a new radioligand for α1-adrenoceptors

Abstract

125Iodo2 - β - (4 - hydroxyphenyl) - ethyl - aminomethyl - tetralone (125Iodo BE 2254 or IBE 2254), a new iodinated radioligand of high specific radioactivity (2175 Ci/mmol), was synthesized and used to characterize α1-adrenoceptors in rat lung and cerebral cortex membranes. The binding constants of IBH 2254, using rat lung and cortex membranes, were KD = 53 ± 10 pM. Bmax = 53 ± 8 fmol/mg; and KD = 78 ± 14 pM, Bmax = 210 ± 26 fmol/mg, respectively (KD = dissociation constant of IBH 2254 determined in saturation experiments). In equilibrium binding experiments with IBH 2254, at concentrations of the free ligand up to 1.2 nM, only one class of binding sites could be detected. In kinetic experi..