Mechanism of insulin action on resting membrane potential of frog skeletal muscle.
At a concentration that stimulates the Na pump, insulin hyperpolarizes the plasma membrane of frog sartorius in the presence of substrate-free Ringer. The hyperpolarization ranged from 3.5 to 7.3 mV and averaged 4.7 mV. Ouabain, 10(-4) M, completely blocked the effect of insulin on the membrane potential. Moreover, ouabain completely reversed the insulin-induced hyperpolarization within 20 min. The hyperpolarization produced by insulin was not associated with a detectable increase in the ratio of K+ permeability to Na+ permeability nor with a detectable increase in the concentration of intracellular K+, although a depletion of K+ near the external surface of the membrane cannot be excluded. The results clearly indicate that the hyperpolarization is secondary to stimulation of the Na pump by insulin.
D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009132:Muscles / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011894:Rana pipiens / Q000502:physiology; D012964:Sodium / Q000378:metabolism*
D007328:Insulin; D010042:Ouabain; D012964:Sodium; D011188:Potassium