Insulin does not hyperpolarize rat muscle by means of a ouabain-inhibitable process.
Experiments were designed to test the hypothesis that insulin-induced hyperpolarization of rat skeletal muscle is mediated by stimulation of a ouabain-inhibitable electrogenic pump. Parallel experiments were carried out on rat caudofemoralis with isoproterenol, known to hyperpolarize rat skeletal muscle by stimulation of such a pump. Ouabain (10(-5) M) completely inhibited isoproterenol-induced hyperpolarization within 15 min but had no effect on half-maximal insulin-induced hyperpolarization. Ouabain (10(-6) M) inhibited isoproterenol effect by 60% during a period of 5-15 min. Ouabain (10(-4) M) had no effect on insulin-induced hyperpolarization within 10 min but depolarized during the next 10 min. In a separate series of studies in rat extensor digitorum longus muscle, 10(-5) M ouabain increased intracellular Na+ within 14 min. It is concluded that in rat caudofemoralis muscle, insulin-induced hyperpolarization is not mediated by a ouabain-inhibitable electrogenic pump.
D000818:Animals; D007328:Insulin / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000502:physiology; D012964:Sodium / Q000378:metabolism
D007328:Insulin; D010042:Ouabain; D012964:Sodium; D007545:Isoproterenol