Effects of internal Na and external K concentrations on Na/K coupling of Na,K-pump in frog skeletal muscle.
To clarify the dependency of the Na/K coupling of the Na,K-pump on internal Na and external K concentrations in skeletal muscle, the ouabain-induced change in membrane potential, the ouabain-induced change in Na efflux and the membrane resistance were measured at various internal Na and external K concentrations in bullfrog sartorius muscle. Upon raising the internal Na concentration from 6 mmol/kg muscle water to 20 mmol/kg muscle water, the magnitude of the ouabain-induced change in membrane potential increased about eightfold and the magnitude of the ouabain-induced change in Na efflux increased about fivefold while the membrane resistance was not significantly changed. As the external K concentration increased from 1 to 10 mM, the magnitude of the ouabain-induced change in membrane potential decreased (1/5.5 fold), while the magnitude of the ouabain-induced change in Na efflux increased (about 1.5-fold). The membrane resistance decreased upon raising the external K concentration from 1 to 10 mM (1/2-fold). These observations imply that the values of the Na/K coupling of the Na,K-pump increases upon raising the internal Na concentration and decreases upon raising the external K concentration.
Marunaka
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Department of Physiology, Shiga University of Medical Science, Ohtsu, Japan.
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D009132:Muscles / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011892:Rana catesbeiana; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013816:Thermodynamics
D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium