Glucagon-like peptide-1 increases cAMP but fails to augment contraction in adult rat cardiac myocytes

Martín G. Vila Petroff, Josephine M. Egan, Xiaolin Wang, Steven J. Sollott

Research output: Contribution to journalArticle

Abstract

The gut hormone, glucagon-like peptide-1 (GLP-1), which is secreted in nanomolar amounts in response to nutrients in the intestinal lumen, exerts cAMP/protein kinase A-mediated insulinotropic actions in target endocrine tissues, but its actions in heart cells are unknown. GLP-1 (10 nmol/L) increased intracellular cAMP (from 5.7±0.5 to 13.1±0.12 pmol/mg protein) in rat cardiac myocytes. The effects of cAMP-doubling concentrations of both GLP-1 and isoproterenol (ISO, 10 nmol/L) on contraction amplitude, intracellular Ca2+ transient (CaT), and pHi in indo-1 and seminaphthorhodafluor (SNARF)-1 loaded myocytes were compared. Whereas ISO caused a characteristic increase (above baseline) in contraction amplitude (160±34%) and CaT (70±5%), GLP-1 induced a significant decrease in contraction amplitude (-27±5%) with no change in the CaT after 20 minutes. Neither pertussis toxin treatment nor exposure to the cGMP-stimulated phosphodiesterase (PDE2) inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine or the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine nor the phosphatase inhibitors okadaic acid or calyculin A unmasked an ISO-mimicking response of GLP-1. In SNARF-1-loaded myocytes, however, both ISO and GLP-1 caused an intracellular acidosis (ΔpHi -0.09±0.02 and -0.08±0.03, respectively). The specific GLP-1 antagonist exendin 9-39 and the cAMP inhibitory analog Rp-8CPT-cAMPS inhibited both the GLP-1-induced intracellular acidosis and the negative contractile effect. We conclude that in contrast to β-adrenergic signaling, GLP-1 increases cAMP but fails to augment contraction, suggesting the existence of functionally distinct adenylyl cyclase/cAMP/protein kinase A compartments, possibly determined by unique receptor signaling microdomains that are not controlled by pertussis toxin-sensitive G proteins or by enhanced local PDE or phosphatase activation. Furthermore, GLP-1 elicits a cAMP-dependent modest negative inotropic effect produced by a decrease in myofilament-Ca2+ responsiveness probably resulting from intracellular acidification.

Original languageEnglish (US)
Pages (from-to)445-452
Number of pages8
JournalCirculation Research
Volume89
Issue number5
Publication statusPublished - Aug 31 2001
Externally publishedYes

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Keywords

  • Calcium
  • cAMP
  • Cardiac myocytes
  • Glucagon-like peptide-1

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Vila Petroff, M. G., Egan, J. M., Wang, X., & Sollott, S. J. (2001). Glucagon-like peptide-1 increases cAMP but fails to augment contraction in adult rat cardiac myocytes. Circulation Research, 89(5), 445-452.