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Pflügers Archiv

, Volume 434, Issue 4, pp 457–465 | Cite as

Effects of reduced electrochemical Na+ gradient on contractility in skeletal muscle: role of the Na+-K+ pump

  • K. Overgaard
  • Ole Bækgaard Nielsen
  • Torben Clausen
ORIGINAL ARTICLE

Abstract

 Continued excitation of skeletal muscle may induce a combination of a low extracellular Na+ concentration ([Na+]o) and a high extracellular K+ concentration ([K+]o) in the T-tubular lumen, which may contribute to fatigue. Here, we examine the role of the Na+-K+ pump in the maintenance of contractility in isolated rat soleus muscles when the Na+, K+ gradients have been altered. When [Na+]o is lowered to 25 mM by substituting Na+ with choline, tetanic force is decreased to 30% of the control level after 60 min. Subsequent stimulation of the Na+-K+ pump with insulin or catecholamines induces a decrease in [Na+]i and hyperpolarization. This is associated with a force recovery to 80–90% of the control level which can be abolished by ouabain. This force recovery depends on hyperpolarization and is correlated to the decrease in [Na+]i (r = 0.93; P<0.001). The inhibitory effect of a low [Na+]o on force development is considerably potentiated by increasing [K+]o. Again, stimulation of the Na+-K+ pump leads to rapid force recovery. The Na+-K+ pump has a large potential for rapid compensation of the excitation-induced rundown of Na+, K+ gradients and contributes, via its electrogenic effect, to the membrane potential. We conclude that these actions of the Na+-K+ pump are essential for the maintenance of excitability and contractile force.

Key words Na+-K+ pump Membrane potential Muscle fatigue Catecholamines Insulin Soleus 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • K. Overgaard
    • 1
  • Ole Bækgaard Nielsen
    • 1
  • Torben Clausen
    • 1
  1. 1.Department of Physiology, University of Aarhus, Ole Worms Alle 160, 8000 Århus C, DenmarkDK

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