title: Receptor identification and physiological characterisation of glucagon-like peptide-2 in the rat heart.
abstract: OBJECTIVE
  The anorexigenic glucagon-like peptide (GLP)-2 is produced by intestinal L cells and released in response to food intake. It affects intestinal function involving G-protein-coupled receptors. To verify whether GLP-2 acts as a cardiac modulator in mammals, we analysed, in the rat heart, the expression of GLP-2 receptors and the myocardial and coronary responses to GLP-2.
  
  
  RESULTS
  GLP-2 receptors were detected on ventricular extracts by quantitative real-time polymerase chain reaction (Q-RT-PCR) and Western blotting. Cardiac GLP-2 effects were analysed on Langendorff perfused hearts. Intracellular GLP-2 signalling was investigated on Langendorff perfused hearts and by Western blotting and enzyme-linked immunosorbent assay (ELISA) on ventricular extracts. By immunoblotting and Q-RT-PCR, we revealed the expression of ventricular GLP-2 receptors. Perfusion analyses showed that GLP-2 induces positive inotropism at low concentration (10-12 mol l(-1)), and negative inotropism and lusitropism from 10 to 10 mol l(-1). It dose-dependently constricts coronaries. The negative effects of GLP-2 were independent from GLP-1 receptors, being unaffected by exendin-3 (9-39) amide. GLP-2-dependent negative action involves Gi/o proteins, associates with a reduction of intracellular cyclic adenosine monophosphate (cAMP), an increase in extracellular signal regulated kinases 1 and 2 (ERK1/2) and a decrease in phospholamban phosphorylation, but is independent from endothelial nitric oxide synthase (eNOS) and protein kinase G (PKG). Finally, GLP-2 competitively antagonised β-adrenergic stimulation.
  
  
  CONCLUSIONS
  For the first time, to our knowledge, we found that: (1) the rat heart expresses functional GLP-2 receptors; (2) GLP-2 acts on both myocardium and coronaries, negatively modulating both basal and β-adrenergic stimulated cardiac performance; and (3) GLP-2 effects are mediated by G-proteins and involve ERK1/2.
authors.affiliation: Department of Cell Biology, University of Calabria, Arcavacata di Rende (CS), Italy.
authors.forename: T
authors.initials: T
authors.lastname: Angelone
authors.forename: E
authors.initials: E
authors.lastname: Filice
authors.forename: A M
authors.initials: AM
authors.lastname: Quintieri
authors.forename: S
authors.initials: S
authors.lastname: Imbrogno
authors.forename: N
authors.initials: N
authors.lastname: Amodio
authors.forename: T
authors.initials: T
authors.lastname: Pasqua
authors.forename: D
authors.initials: D
authors.lastname: Pellegrino
authors.forename: F
authors.initials: F
authors.lastname: Mulè
authors.forename: M C
authors.initials: MC
authors.lastname: Cerra
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002316:Cardiotonic Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D053767:Glucagon-Like Peptide 2 / Q000494:pharmacology*; D000067757:Glucagon-Like Peptide-1 Receptor; D000067758:Glucagon-Like Peptide-2 Receptor; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D020935:MAP Kinase Signaling System; D008297:Male; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D018027:Receptors, Glucagon / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002316:Cardiotonic Agents; C000593835:Glp1r protein, rat; D053767:Glucagon-Like Peptide 2; D000067757:Glucagon-Like Peptide-1 Receptor; D000067758:Glucagon-Like Peptide-2 Receptor; D010446:Peptide Fragments; D018027:Receptors, Glucagon; C083773:exendin (9-39); D000242:Cyclic AMP; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D017869:Cyclic GMP-Dependent Protein Kinases