Endothelial nitric oxide synthase decreases β-adrenergic responsiveness via inhibition of the L-type Ca2+ current

Honglan Wang, Mark J. Kohr, Debra G. Wheeler, Mark T. Ziolo

Research output: Contribution to journalArticlepeer-review

Abstract

Signaling via endothelial nitric oxide synthase (NOS3) limits the heart's response to β-adrenergic (β-AR) stimulation, which may be protective against arrhythmias. However, mechanistic data are limited. Therefore, we performed simultaneous measurements of action potential (AP, using patch clamp), Ca2+ transients (fluo 4), and myocyte shortening (edge detection). L-type Ca2+ current (ICa) was directly measured by the whole cell ruptured patchclamp technique. Myocytes were isolated from wild-type (WT) and NOS3 knockout (NOS3-/-) mice. NOS3-/- myocytes exhibited a larger incidence of β-AR (isoproterenol, 1 μM)-induced early afterdepolarizations (EADs) and spontaneous activity (defined as aftercontractions). We also examined ICa, a major trigger for EADs. NOS3-/- myocytes had a significantly larger β-AR-stimulated increase in ICa compared with WT myocytes. In addition, NOS3 -/- myocytes had a larger response to β-AR stimulation compared with WT myocytes in Ca2+ transient amplitude, shortening amplitude, and AP duration (APD). We observed similar effects with specific NOS3 inhibition [L-N5-(1-iminoethyl)-ornithine (L-NIO), 10 μM] in WT myocytes as with NOS3 knockout. Specifically, L-NIO further increased isoproterenol- stimulated EADs and aftercontractions. L-NIO also further increased the isoproterenol-stimulated ICa, Ca2+ transient amplitude, shortening amplitude, and APD (all P < 0.05 vs isoproterenol alone). L-NIO had no effect in NOS3-/- myocytes. These results indicate that NOS3 signaling inhibits the β-AR response by reducing ICa and protects against arrhythmias. This mechanism may play an important role in heart failure, where arrhythmias are increased and NOS3 expression is decreased.

Original languageEnglish (US)
Pages (from-to)H1473-H1480
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume294
Issue number3
DOIs
StatePublished - Mar 2008
Externally publishedYes

Keywords

  • Action potential
  • Cardiac myocytes
  • Early afterdepolarizations
  • Endothelial nitric oxide synthase

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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