The effect of the internal Na concentration on the electrogenicity of the insulin-stimulated Na,K-pump in frog skeletal muscles.
Insulin induced a hyperpolarization of the membrane by stimulating the Na,K-pump in frog skeletal muscles. The Na,K-pump activity was dependent on the internal Na concentration. As the internal Na concentration was raised from 5 mmol/kg muscle water to 18 mmol/kg muscle water, the magnitude of the insulin-induced increase in the ouabain-sensitive Na efflux (an index of the Na,K-pump activity) rose by 5-fold and the magnitude of the insulin-induced hyperpolarization rose by 8.5-fold. On the other hand, the specific membrane resistance was not significantly changed by a rise in the internal Na concentration. The Na/K coupling of the Na,K-pump was calculated at low, normal or high internal Na concentration by using the values of the insulin-induced changes in the ouabain-sensitive Na efflux and the membrane potential. As a result of the calculation, it was suggested that in frog skeletal muscles the Na/K coupling would increase with a rise of the internal Na concentration.
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011892:Rana catesbeiana; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D007328:Insulin; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase