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Electrogenic sodium pump in rabbit atrio-ventricular node cell.

Y Kurachi·A Noma·H Irisawa
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Abstract

Electrogenicity of the Na pump was demonstrated in rabbit A-V node cells by analyzing the K-induced hyperpolarization occurring after a short period of K-free perfusion. The transient hyperpolarization was abolished completely by strophanthidin (10(-5)M). The membrane slope conductance remained unchanged during the transient hyperpolarization. On perfusion of 50 mM K and K-free incubation the transient hyperpolarization reached --69 mV which was more negative than the expected EK (about --28 mV). The order of potencies of monovalent cations to activate the K site of the Na pump was Tl greater than Rb equal to K greater than NH4 equal to Cs greater than Li, which was similar to the sequence reported in the literature. Michaelis-Menten type activation of the K site of the Na pump was suggested from the relationship between the decay rate constant of the K-induced outward current transient and [K]o. These findings obviously indicate that the Na pump in the A-V node cells shares common characteristics with those of other excitable tissues. Direct contribution of the pump activity to the membrane potential under physiological conditions was suggested by a significant depolarization occurring immediately after application of strophanthidin.

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AnimalsAtrioventricular NodeBiological Transport, ActiveCationsHeart Conduction SystemIn Vitro TechniquesMembrane PotentialsPotassiumRabbitsSodiumJournal Article

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Y Kurachi, A Noma, H Irisawa. 1981. Electrogenic sodium pump in rabbit atrio-ventricular node cell.. https://doi.org/10.1007/bf00581504

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