title: Electrogenic sodium pump in rabbit atrio-ventricular node cell.
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.
mesh_terms: D000818:Animals; D001283:Atrioventricular Node / Q000378:metabolism / Q000502:physiology*; D001693:Biological Transport, Active; D002412:Cations / Q000502:physiology; D006329:Heart Conduction System / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials; D011188:Potassium / Q000502:physiology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism* / Q000502:physiology
chemical_list: D002412:Cations; D012964:Sodium; D011188:Potassium