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

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  • Department of Physiology and Biophysics
  • Department of Sport Science
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.
Original languageEnglish
JournalPflügers Archiv - European Journal of Physiology
Pages (from-to)457-65
Number of pages8
Publication statusPublished - 1997

    Research areas

  • Animals, Electrochemistry, Extracellular Space, Female, Male, Membrane Potentials, Muscle Contraction, Muscle Fibers, Skeletal, Muscle, Skeletal, Osmolar Concentration, Potassium, Rats, Rats, Wistar, Sodium, Sodium-Potassium-Exchanging ATPase, Stimulation, Chemical

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