Intermedin elicits a negative inotropic effect in rat papillary muscles mediated by endothelial-derived nitric oxide

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Pires, AL (Author) Other; Pinho, M (Author) Other; Sena, CM (Author) Other; Seica, R (Author) Other; Leite-Moreira AF (Author) FMUP

Journal

Title: American Journal of Physiology - Heart and Circulatory Physiology

Vol. 302

Pages: H1131-H1137

ISSN: 0363-6135

Publisher: American Physiological Society

Indexing

ISI Web of Knowledge - 11 Citations

Scopus - 12 Citations

Other information

Authenticus ID: P-002-CRW

DOI: 10.1152/ajpheart.00877.2011

Abstract (EN): Pires AL, Pinho M, Sena CM, Seica R, Leite-Moreira AF. Intermedin elicits a negative inotropic effect in rat papillary muscles mediated by endothelial-derived nitric oxide. Am J Physiol Heart Circ Physiol 302: H1131-H1137, 2012. First published January 6, 2011; doi:10.1152/ajpheart.00877.2011.-Intermedin (IMD) is a novel vasoactive peptide from the calcitonin gene-related peptide (CGRP) implicated in cardiac regulation, yet the contractile effects of IMD remain controversial, since previous studies in vivo and isolated cardiomyocytes documented contradictory results. We hypothesized cardiac endothelial cells involvement in IMD modulation of cardiac function as an explanation for these opposing observations. With this in mind, we investigated the direct action of increasing concentrations of IMD (10(-8) to 10(-6)M) on myocardial performance parameters in rat left ventricular (LV) papillary muscles with and without endocardial endothelium (EE) and in presence of receptor antagonists and intracellular pathways inhibitors. In LV papillary muscles with intact EE, IMD induced a concentration-dependent negative inotropic action (%decrease relative to baseline, at IMD concentration of 10(-6)M, active tension of 14 +/- 4%, and maximum velocity of tension rise of 10 +/- 4%). These effects were blunted by EE removal, AM receptor antagonist (AM(22-52)), and CGRP receptor antagonist (CGRP(8-37)). Additionally, nitric oxide (NO) synthase inhibition with N-G-nitro-L-arginine (L-NAME) in muscles with and without EE and guanylyl cyclase inhibition with {1H-[1,2,4]oxadiazole-[4,4-a]-quinoxalin-1-one} not only blunted the negative inotropic action of IMD but also unmasked IMD-positive inotropic effect dependent on CGRP receptor PKA activation. Western blot quantification of phosphorylated cardiac troponin I (P-cTnI) in IMD-treated papillary muscles revealed a significant increase in P-cTnI when compared with untreated muscles, while in L-NAME-pretreated papillary muscles IMD failed to increase P-cTnI. Finally, we found that stimulation of both EE and microvascular endothelial cells with IMD significantly increased NO production by 40 +/- 3 and 38 +/- 3%, respectively, suggesting the role of cardiac endothelial cells in NO production upon IMD stimulation. Our findings establish IMD negative inotropic effect in isolated myocardium due to NO/cGMP pathway activation with concomitant thin myofilament desensitization by increase in cTnI phosphorylation and provide a coherent explanation for the previously reported contradictory results.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7