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Preclinical pharmacological in vitro investigations on low chloride conductance myotonia: effects of potassium regulation

Authors
  • Hoppe, Kerstin1, 2
  • Chaiklieng, Sunisa3, 4
  • Lehmann-Horn, Frank2
  • Jurkat-Rott, Karin5
  • Wearing, Scott6, 7
  • Klingler, Werner6, 8, 7
  • 1 University Hospital Frankfurt, Goethe University Frankfurt, Theodor–Stern–Kai 7, Frankfurt, 60590, Germany , Frankfurt (Germany)
  • 2 University Hospital of Wuerzburg, Oberduerrbacher Str. 6, Wuerzburg, 97080, Germany , Wuerzburg (Germany)
  • 3 Ulm University, Albert Einstein Allee 23, Ulm, 89081, Germany , Ulm (Germany)
  • 4 Khon Kaen University, Muang Khon Kaen, Thailand , Muang Khon Kaen (Thailand)
  • 5 Division of Experimental Anesthesiology, Albert-Einstein-Allee 23, Ullm, 89081, Germany , Ullm (Germany)
  • 6 Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, 4059, Australia , Kelvin Grove (Australia)
  • 7 Technical University of Munich, Gerog-Brauchle-Ring 60/62, Munich, Germany , Munich (Germany)
  • 8 SRH Clinincs, Hohenzollernstraße 40, Sigmaringen, 72488, Germany , Sigmaringen (Germany)
Type
Published Article
Journal
Pflügers Archiv - European Journal of Physiology
Publisher
Springer-Verlag
Publication Date
Aug 03, 2020
Volume
472
Issue
10
Pages
1481–1494
Identifiers
DOI: 10.1007/s00424-020-02410-4
Source
Springer Nature
Keywords
License
Yellow

Abstract

In myotonia, reduced Cl− conductance of the mutated ClC-1 channels causes hindered muscle relaxation after forceful voluntary contraction due to muscle membrane hyperexcitability. Repetitive contraction temporarily decreases myotonia, a phenomena called “warm up.” The underlying mechanism for the reduction of hyperexcitability in warm-up is currently unknown. Since potassium displacement is known to reduce excitability in, for example, muscle fatigue, we characterized the role of potassium in native myotonia congenita (MC) muscle. Muscle specimens of ADR mice (an animal model for low gCl− conductance myotonia) were exposed to increasing K+ concentrations. To characterize functional effects of potassium ion current, the muscle of ADR mice was exposed to agonists and antagonists of the big conductance Ca2+-activated K+ channel (BK) and the voltage-gated Kv7 channel. Effects were monitored by functional force and membrane potential measurements. By increasing [K+]0 to 5 mM, the warm-up phenomena started earlier and at [K+]0 7 mM only weak myotonia was detected. The increase of [K+]0 caused a sustained membrane depolarization accompanied with a reduction of myotonic bursts in ADR mice. Retigabine, a Kv7.2–Kv7.5 activator, dose-dependently reduced relaxation deficit of ADR myotonic muscle contraction and promoted the warm-up phenomena. In vitro results of this study suggest that increasing potassium conductivity via activation of voltage-gated potassium channels enhanced the warm-up phenomena, thereby offering a potential therapeutic treatment option for myotonia congenita.

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