The resolution of agonist alpha 2-adrenergic receptor complexes from unoccupied receptors or antagonist-alpha 2...

Alpha 2-adrenergic receptors linked to inhibition of adenylate cyclase activity in human platelet membranes can be isolated using DEAE chromatography following solubilization into digitonin-containing buffers. This procedure permits resolution of agonist-occupied receptors from antagonist-occupied receptors. Antagonist-occupied receptors co-elute with unoccupied receptors. Adenylate cyclase activity elutes independently of all alpha 2-receptor activities. A greater resolution of agonist-receptor complexes from antagonist-receptor complexes is obtained using DEAE chromatography than reported earlier using approaches that rely entirely on agonist-stabilized increases in apparent receptor size. Consequently, DEAE chromatography may be of considerable value in isolating these agonist-receptor complexes to permit identification of the membrane component(s) which are more stably associated with the receptor subsequent to agonist occupancy and thus might be involved in receptor-cyclase coupling.