BINDING OF AGONISTS AND ANTAGONISTS TO THE PORCINE ADIPOSE-TISSUE BETA-ADRENERGIC RECEPTOR(S)

1. Affinities of agonists for porcine adipose tissue beta-adrenergic r eceptors, determined by competitive ligand binding with H-3-dihydroalp renolol to crude adipose tissue membranes in vitro, varied from 50 tim es > to 25 times < than isoproterenol. Affinities for antagonists vari ed from 8 times > to 1000 times < propranolol. 2. Receptor affinity wa s not related to the ability to stimulate or inhibit lipolysis, or to the agonist or antagonist purported receptor subtype specificity. 3. M odeling of ligand-binding data indicated more than one binding site fo r several ligands. The assignment of beta-adrenergic subtypes to the i ndividual binding sites was unclear because this would depend on the i ndividual ligands used to establish binding sites.