Potassium Translocation by the Na+/K+ Pump is Voltage Insensitive

The voltage dependence of steady and transient changes in Na+/K+ pump current, in response to step changes in membrane potential, was investigated in guinea pig ventricular myocytes voltage clamped and internally dialyzed under experimental conditions designed to support four separate modes of Na+/K...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1988-05, Vol.85 (10), p.3412-3416
Main Authors: Bahinski, Anthony, Nakao, Masakazu, Gadsby, David C.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Capacitance
Cell membranes
Cell physiology
Electric current
Electric potential
Enzymes
Fundamental and applied biological sciences. Psychology
Guinea Pigs
Heart - physiology
In Vitro Techniques
Kinetics
Membrane and intracellular transports
Membrane potential
Membrane Potentials - drug effects
Molecular and cellular biology
Myocardium - enzymology
Pipettes
Potassium - metabolism
Pumps
Sodium-Potassium-Exchanging ATPase - metabolism
Steady state current
Strophanthidin - pharmacology
Ventricular Function
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Summary:The voltage dependence of steady and transient changes in Na+/K+ pump current, in response to step changes in membrane potential, was investigated in guinea pig ventricular myocytes voltage clamped and internally dialyzed under experimental conditions designed to support four separate modes of Na+/K+ pump activity. Voltage jumps elicited transient pump currents when the pump cycle was running forward or backward, or when pumps were limited to Na+ translocation, but not when they were made to carry out K+/K+ exchange. This result indicates that K+ translocation involves no net charge movement across the membrane field and is therefore voltage insensitive. The transient pump currents seen during Na+/K+ transport demonstrate that both forward and reverse pump cycles are rate limited not by the voltage-dependent step but by a voltage-independent step, probably K+ translocation. These findings severely constrain kinetic models of Na+/K+ pump activity.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.85.10.3412