title: RAMP2 and RAMP3 mRNA levels are increased in failing rat cardiomyocytes and associated with increased responsiveness to adrenomedullin.
abstract: Adrenomedullin (AM) is a potent vasorelaxing peptide with natriuretic and diuretic actions. Recent data indicate that AM may function as an endogenous regulator of cardiac function. We investigated to what extent AM, the AM receptor subtypes, and AM receptor-associated proteins were regulated in cardiomyocytes and non-cardiomyocytes of rats with congestive heart failure (CHF), and whether such regulation was paralleled by corresponding alterations of functional responses to AM. Cardiomyocytes and non-cardiomyocytes were isolated from myocardial tissue of rats 7 days after induction of myocardial infarction or sham operation. AM immunoreactivity was found in cardiomyocytes, endothelial cells, and fibroblasts. Robust increase of AM mRNA levels was observed both in the cardiomyocytes and in the non-cardiomyocytes of CHF rats compared to that of sham-operated rats (2.7-fold and 3.7-fold, respectively, P <0.05). Fairly high mRNA levels and immunoreactivity against the AM receptor chaperone receptor activity-modifying protein-2 (RAMP2) were also detected in the cardiomyocytes and non-cardiomyocytes. However, induction of RAMP2 mRNA expression was restricted to cardiomyocytes (1.8-fold increase in cardiomyocytes from CHF rats vs. sham rats; P <0.05). In contrast, very low levels of RAMP3 mRNA were observed. RAMP3 mRNA levels, however, were elevated in both cardiomyocytes and non-cardiomyocytes from CHF rats (6.5-fold and 2.4-fold increase vs. sham rats, respectively; P <0.05). Parallel increases of specific AM receptor binding sites and of AM-stimulated adenylyl cyclase activities were observed in failing cardiomyocytes compared to cardiomyocytes from sham rats (fivefold and sixfold increase, respectively; P <0.05). Thus, this study demonstrates that AM mRNA levels, AM receptor binding sites, and AM-stimulated adenylyl cyclase activities are increased in cardiomyocytes from failing rat hearts. Furthermore, our data suggest that induction of RAMP2 and RAMP3 contributes to the increased responsiveness to AM in failing cardiomyocytes.
authors.affiliation: MSD Cardiovascular Research Center, Rikshospitalet University Hospital, University of Oslo, N-0027 Oslo, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Øie
authors.forename: Leif Erik
authors.initials: LE
authors.lastname: Vinge
authors.forename: Geir Øystein
authors.initials: GØ
authors.lastname: Andersen
authors.forename: Arne
authors.initials: A
authors.lastname: Yndestad
authors.forename: Kurt A
authors.initials: KA
authors.lastname: Krobert
authors.forename: Cecilie
authors.initials: C
authors.lastname: Sandberg
authors.forename: Mohammed Shakil
authors.initials: MS
authors.lastname: Ahmed
authors.forename: Terje
authors.initials: T
authors.lastname: Haug
authors.forename: Finn Olav
authors.initials: FO
authors.lastname: Levy
authors.forename: Tor
authors.initials: T
authors.lastname: Skomedal
authors.forename: Håvard
authors.initials: H
authors.lastname: Attramadal
mesh_terms: D053607:Adrenomedullin; D000818:Animals; D005786:Gene Expression Regulation; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology; D006439:Hemodynamics / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D008168:Lung / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009929:Organ Size; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D058265:Receptors, Adrenomedullin; D018000:Receptors, Peptide / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010455:Peptides; D012333:RNA, Messenger; C545509:Ramp2 protein, rat; C545510:Ramp3 protein, rat; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D058265:Receptors, Adrenomedullin; D018000:Receptors, Peptide; D053607:Adrenomedullin