After a 20 min initial washout, the rate of loss of radioactively labeled sodium ions from sodium-enriched muscle cells is sensitive to the external sodium and potassium ion concentrations. In the absence of external potassium ions, the presence of external sodium ions increases the sodium efflux. In the presence of external potassium ions, the presence of external sodium ions decreases the sodium efflux. In the absence of external potassium ions about one-third of the Na+ efflux that depends upon the external sodium ion concentration can be abolished by 10-5 M glycoside. The glycoside-insensitive but external sodium-dependent Na+ efflux is uninfluenced by external potassium ions. In the absence of both external sodium and potassium ions the sodium efflux is relatively insensitive to the presence of 10-5 M glycoside. The maximal external sodium-dependent sodium efflux in the absence of external potassium ions is about 20% of the magnitude of the maximal potassium-dependent sodium efflux. The magnitude of the glycoside-sensitive sodium efflux in K-free Ringer solution is less than 10% of that observed when sodium efflux is maximally activated by potassium ions. The inhibition of the potassium-activated sodium efflux by external sodium ions is of the competitive type. Reducing the external sodium ion concentration displaces the plots of sodium extrusion rate vs. [K]o to the left and upwards.
Article|
February 01 1971
The Kinetics of Sodium Extrusion in Striated Muscle As Functions of the External Sodium and Potassium Ion Concentrations
R. A. Sjodin
R. A. Sjodin
From the Department of Biophysics, University of Maryland School of Medicine, Baltimore, Maryland 21201
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R. A. Sjodin
From the Department of Biophysics, University of Maryland School of Medicine, Baltimore, Maryland 21201
Received:
May 22 1970
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1971 by The Rockefeller University Press
1971
J Gen Physiol (1971) 57 (2): 164–187.
Article history
Received:
May 22 1970
Citation
R. A. Sjodin; The Kinetics of Sodium Extrusion in Striated Muscle As Functions of the External Sodium and Potassium Ion Concentrations . J Gen Physiol 1 February 1971; 57 (2): 164–187. doi: https://doi.org/10.1085/jgp.57.2.164
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