Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 339, Issue 3, pp 327–331

Cromakalim (BRL 34915) restores in vitro the membrane potential of depolarized human skeletal muscle fibres

  • A. Spuler
  • F. Lehmann-Horn
  • P. Grafe
Article

DOI: 10.1007/BF00173587

Cite this article as:
Spuler, A., Lehmann-Horn, F. & Grafe, P. Naunyn-Schmiedeberg's Arch Pharmacol (1989) 339: 327. doi:10.1007/BF00173587

Summary

The purpose of the present study was to analyze the effects of cromakalim (BRL 34915), a potent drug from a new class of drugs characterized as “K+ channel openers”, on the electrical activity of human skeletal muscle. Therefore, intracellular recordings were used to measure the effects of cromakalim on the membrane potential and input conductance of fibres from human skeletal muscle biopsies. Cromakalim in a concentration above 1 μmol/l induced an increase in membrane K+ conductance. This effect resulted in a membrane hyperpolarization. The magnitude of this polarization depended on the difference between resting and K+ equilibrium potential. The effect had a rapid onset and was quickly reversible after washing. Fibres from two patients with hyperkalaemic periodic paralysis showed an excessive membrane depolarization during and also after exposure to an slightly elevated extracellular K+ concentration. In the latter situation, cromakalim repolarized the fibres to the normal resting potential. Tolbutamide (1 mmol/l) and Ba2+ (3 mmol/l) strongly antagonized the effect of cromakalim. The data show that cromakalim hyperpolarizes depolarized human skeletal muscle fibres maintained in vitro. The underlying mechanism is probably an activation of otherwise “silent”, ATP-regulated K+ channels. Such an effect may be of therapeutic benefit in a situation in which a membrane depolarization causes muscle paralysis.

Keywords

Cromakalim K+-channels Tolbutamide Human skeletal muscle Hyperkalaemic periodic paralysis 

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • A. Spuler
    • 1
  • F. Lehmann-Horn
    • 2
  • P. Grafe
    • 1
  1. 1.Department of PhysiologyUniversity of MunichMünchen 2Federal Republic of Germany
  2. 2.Department of NeurologyTechnical University of MunichMünchen 80Federal Republic of Germany

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