Expression of glucagon-like peptide 1 receptor in a murine C cell line: regulation of calcitonin gene by glucagon-like peptide 1.

We have characterized, by RT-PCR amplification using specific primers, the presence of glucagon-like peptide-1 (GLP-I) receptor mRNA in CA-77 cells, a C cell line derived from a rat medullary thyroid carcinoma. Down-regulation of the GLP-1 receptor mRNA was observed after exposure of CA-77 C cells with GLP-1 (7-37). Increased secretion of both calcitonin gene-related peptide (CGRP) and calcitonin (CT) occurred after treatment with GLP-1 (7-37) associated with elevated steady-state levels of CGRP and CT mRNA. GLP-1 (7-37) increased cAMP formation in CA-77 cells in a dose-dependent manner; exendin (9-39), a GLP-1 receptor antagonist, inhibited cAMP production. The GLP-1 peptide which is produced by intestinal cells could be involved in the control of CT secretion through an entero-thyroidal axis implying GLP-1 receptor and increased CT gene expression.