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Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon

Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated us...

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Detalles Bibliográficos
Autores principales: Adelman, William J., Moore, John W.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1961
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2195157/
https://www.ncbi.nlm.nih.gov/pubmed/13681454
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author Adelman, William J.
Moore, John W.
author_facet Adelman, William J.
Moore, John W.
author_sort Adelman, William J.
collection PubMed
description Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated using the Nernst relation and constant activity coefficients. While an axon bathed in artificial sea water shows a slow increase in internal sodium concentration, the rate of sodium accumulation is increased about two times by reducing external calcium and magnesium concentrations to 0.1 times their normal values. The mean inward net sodium flux increases from a mean control value of 97 pmole/cm(2) sec. to 186 pmole/cm(2) sec. in low divalent solution. Associated with these effects of external divalent ion reduction are a marked decrease in action potential amplitude, little or no change in resting potential, and a shift along the voltage axis of the curve relating peak sodium conductance to membrane potential similar to that obtained by Frankenhaeuser and Hodgkin (1957). These results implicate divalent ions in long term (minutes to hours) sodium permeability.
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spelling pubmed-21951572008-04-23 Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon Adelman, William J. Moore, John W. J Gen Physiol Article Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated using the Nernst relation and constant activity coefficients. While an axon bathed in artificial sea water shows a slow increase in internal sodium concentration, the rate of sodium accumulation is increased about two times by reducing external calcium and magnesium concentrations to 0.1 times their normal values. The mean inward net sodium flux increases from a mean control value of 97 pmole/cm(2) sec. to 186 pmole/cm(2) sec. in low divalent solution. Associated with these effects of external divalent ion reduction are a marked decrease in action potential amplitude, little or no change in resting potential, and a shift along the voltage axis of the curve relating peak sodium conductance to membrane potential similar to that obtained by Frankenhaeuser and Hodgkin (1957). These results implicate divalent ions in long term (minutes to hours) sodium permeability. The Rockefeller University Press 1961-09-01 /pmc/articles/PMC2195157/ /pubmed/13681454 Text en Copyright © Copyright, 1962, by The Rockefeller Institute Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Article
Adelman, William J.
Moore, John W.
Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title_full Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title_fullStr Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title_full_unstemmed Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title_short Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
title_sort action of external divalent ion reduction on sodium movement in the squid giant axon
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2195157/
https://www.ncbi.nlm.nih.gov/pubmed/13681454
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