The β-adrenergic receptor in human lymphocytes: Subclassification by the use of a new radio-ligand, (±)-125iodocyanopindolol

Abstract

(±)-125Iodocyanopindolol (ICYP), a new radio-ligand with high affinity and specificity to β-adrenoceptors was used to identify and characterized β-adrenergic receptors in human lymphocytes. Binding of ICYP was saturable with 1.56 ± 0.2 fmol ICYP specifically bound/106 cells at maximal occupancy of the sites and of high affinity (KD=57 ± 7.1pM, N=4. In contrast to 125Iodohydroxybenzylpindolol ICYP-binding was not affected by phentolamine (up to 10-4M) or serotin (up to 10-5M). Analysis of inhibition of ICYP-binding via a pseudo-Scatchard-plot ("Hofstee-plot") by β1-selective (practocol, metaprolol) and β2-selective (IPS 339, zinterol) adrenergic drugs resulted in linear plots suggesting the e..