Distinction of Receptor from Nonreceptor Interactions in Binding Studies

Abstract

Studies of the binding of ligands to various putative pharmacologic receptors are entering a new phase. Over the past decade, sufficient expertise has been developed to measure with confidence the binding of highly radioactively labeled probes to quantitatively small numbers of high-affinity binding sites, which in most cases represent pharmacologic receptors of interest. Now, these techniques are being employed to study receptors for an ever-burgeoning number of pharmacologically active agents [Cuatrecasas and Hollenberg (1976); collection of reviews edited by Blecher (1976)]. Furthermore, it is becoming apparent that the task of assessing receptor characteristics by ligand binding studies (e.g., receptor changes related to desensitization phenomena) may require a more sophisticated approach than may have been initially considered adequate. It thus appears appropriate to develop an overview for such studies, particularly from the point of view of distinguishing ligand binding sites which typify “true” receptor characteristics (therefore specific binding sites) from those cellular binding sites which do not reflect receptor properties (therefore nonspecific or nonreceptor binding sites).