Characterization of CGRP receptor binding

CGRP receptor binding may be measured using homogenates of cell membranes or intact cells. Here a microcentrifugation-based assay is described that utilizes radioiodinated CGRP in displacement studies to determine the binding parameters for any ligand that interacts with CGRP receptors. A similar assay is described for binding to cultured cells. The protocols may be adapted for other radioligands or for filtration-based assays. The main problems with CGRP binding assays can usually be traced to degradation of the radioligand or displacing ligands. Also, some cell lines fail to express CGRP receptors after extensive passage. CGRP binding assays provide a rapid and easy approach for distinguishing between receptors for CGRP and related peptides such as adrenomedullin and amylin.