The influence of strophanthidin, ouabain, and the removal of external sodium on the sodium efflux from frog sartorius muscle was measured. In freshly dissected muscles strophanthidin and ouabain in maximally effective concentrations reduced the efflux of sodium by about 50%. Of the sodium efflux which is strophanthidin-insensitive about 75% is inhibited after complete replacement of external sodium by lithium. In the absence of strophanthidin replacement of external sodium by lithium, calcium, or magnesium produces an initial rise in the sodium efflux, followed by a fall in the efflux as the exposure of the muscles to sodium-free media is continued. When the muscles are exposed for prolonged periods in sodium-free media, the fraction of internal sodium lost per minute is higher when returned to normal Ringer fluid than it was initially. The activation of sodium efflux by external sodium after long periods in sodium-free solutions is partly strophanthidin-sensitive and partly strophanthidin-insensitive. The internal sodium concentration is an important factor in these effects. The effects of temperature on the sodium efflux were also measured. Above 7°C the Q10 of both the strophanthidin-sensitive and strophanthidin-insensitive sodium efflux is about 2.0. Below 7°C the strophanthidin-insensitive sodium efflux has a Q10 of about 7.4.
Article|
March 01 1970
Fractionation of Sodium Efflux in Frog Sartorius Muscles by Strophanthidin and Removal of External Sodium
P. Horowicz,
P. Horowicz
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
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J. W. Taylor,
J. W. Taylor
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
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D. M. Waggoner
D. M. Waggoner
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
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P. Horowicz
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
J. W. Taylor
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
D. M. Waggoner
From the Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706.
Dr. Horowicz's present address is Department of Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14620.
Received:
June 04 1969
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1970 by The Rockefeller University Press
1970
J Gen Physiol (1970) 55 (3): 401–425.
Article history
Received:
June 04 1969
Citation
P. Horowicz, J. W. Taylor, D. M. Waggoner; Fractionation of Sodium Efflux in Frog Sartorius Muscles by Strophanthidin and Removal of External Sodium . J Gen Physiol 1 March 1970; 55 (3): 401–425. doi: https://doi.org/10.1085/jgp.55.3.401
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