Receptors for calcitonin gene-related peptide on the rat liver plasma membranes

Specific binding sites for calcitonin gene-related peptide (CGRP) were identified in the rat liver plasma membrane. The binding of 125I-[TyrO]rat CGRP to rat liver plasma membrane was time dependent, saturable and reversible. Scatchard analysis of the data revealed a single class of binding sites with apparent dissociation constant of 260.8 pM and a maximal binding capacity of 26.6 fmol/mg of protein. Rat, chick, and human CGRP and their synthetic analogues inhibited label binding in a dose-dependent manner with relative potencies as follows; chick greater than rat greater than human greater than [TyrO]rat CGRP. Salmon, human and [Asu1'7]eel calcitonin also inhibited label binding but only at higher concentrations. These results clearly indicate the presence of specific binding sites for CGRP in rat liver plasma membrane and suggest that CGRP has possible biological actions on the rat liver.