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Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
10:53

Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents

Published on: July 3, 2013

The MLCK-mediated alpha1-adrenergic inotropic effect in atrial myocardium is negatively modulated by PKCepsilon

Michael Grimm1, Nina Mahnecke, Friederike Soja

  • 1Institute of Experimental and Clinical Pharmacology and Toxicology, University Medical Center, Hamburg, Germany.

British Journal of Pharmacology
|June 20, 2006
PubMed

Insights

Alpha(1)-adrenergic stimulation enhances atrial contraction via myosin light chain kinase (MLCK). Protein kinase C epsilon (PKCepsilon) activation negatively modulates this effect, while PKCalpha and IP(3) receptors are not involved.

Area of Science:

  • Cardiovascular Physiology
  • Molecular Cardiology
  • Adrenergic Signaling

Background:

  • Alpha(1)-adrenergic stimulation plays a crucial role in regulating cardiac contractility.
  • The precise molecular mechanisms, including the involvement of specific kinases and receptors, in mediating the positive inotropic effect in atrial myocardium remain incompletely understood.
  • Investigating these pathways is essential for understanding cardiac function and potential therapeutic targets.

Purpose of the Study:

  • To elucidate the roles of myosin light chain kinase (MLCK), protein kinase C (PKC) isozymes, and the inositol 1,4,5-trisphosphate (IP(3)) receptor in the positive inotropic effect of alpha(1)-adrenergic stimulation in atrial tissue.
  • To determine the specific contribution of PKCepsilon and PKCalpha to this signaling pathway.
  • To clarify the involvement of IP(3) receptors in mediating the inotropic response.

Main Methods:

  • Isolated left atrial preparations from male FVB mice were used to measure inotropic effects.
  • Phenylephrine was administered in a concentration-dependent manner to assess its impact on force of contraction.
  • Specific inhibitors and peptides were employed to investigate the roles of MLCK, PKCepsilon, PKCalpha, and IP(3) receptors, including ML-7, wortmannin, KIE1-1, KIC1-1, chelerythrine, and 2-APB.

Main Results:

  • Phenylephrine significantly increased the force of contraction in a concentration-dependent manner.
  • This effect was associated with increased MLC-2a phosphorylation and translocation of PKCepsilon, but not PKCalpha, to cellular fractions.
  • MLCK inhibition reduced the inotropic effect, while PKCepsilon translocation inhibition augmented it, indicating a negative modulatory role for PKCepsilon. PKCalpha and IP(3) receptor inhibition did not affect the phenylephrine-induced inotropic response.

Conclusions:

  • Activation of MLCK is essential for the positive inotropic effect mediated by alpha(1)-adrenergic stimulation in the atrial myocardium.
  • Ca(2+)-independent PKCepsilon acts as a negative modulator of this alpha(1)-adrenergic-induced positive inotropic effect.
  • PKCalpha and IP(3) receptor activation are not involved in this specific signaling pathway.

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