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Regulation by magnesium of intracellular calcium movement in skinned muscle fibers
The effect of Mg on Ca movement between the sarcoplasmic reticulum (SR) and myofilament space (MFS) was studied in skinned muscle fibers by using isometric force as an indicator of MFS Ca. In Ca-loaded fibers at 20 degrees C, the large force spike induced by Ca in 1 mM Mg (5 mM ATP) was strongly inh...
Formato: | Texto |
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Lenguaje: | English |
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The Rockefeller University Press
1977
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215045/ https://www.ncbi.nlm.nih.gov/pubmed/299886 |
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collection | PubMed |
description | The effect of Mg on Ca movement between the sarcoplasmic reticulum (SR) and myofilament space (MFS) was studied in skinned muscle fibers by using isometric force as an indicator of MFS Ca. In Ca-loaded fibers at 20 degrees C, the large force spike induced by Ca in 1 mM Mg (5 mM ATP) was strongly inhibited in 3 mM Mg, and force development was extremely slow. After a brief Ca stimulus in 1 mM Mg, relaxation in Ca-free solution was significantly faster in 3 mM Mg. These changes were due to altered Ca movements, since the effect of 3 mM Mg on steady force in CaEGTA solutions was small. Changes in Mg alone induced force transients apparently due to altered Ca movement. In relaxed fibers, decreasing the Mg to 0.25 mM caused phasic force development. In contracting fibers in Ca solutions, increasing the Mg caused a large transient relaxation. The effects of increased Mg were antagonized by 0.5 mM Cd, an inhibitor of the SR Ca transport system. The results indicate that active Ca uptake by the SR in situ is stimulated by Mg, and that it can affect local MFS [Ca++] in the presence of a substantial Ca source. These results provide evidence that an increased rate of Ca uptake in 3 mM Mg could account for inhibition of the large force spike associated with Ca-induced Ca release in skinned fibers. |
format | Text |
id | pubmed-2215045 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1977 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22150452008-04-23 Regulation by magnesium of intracellular calcium movement in skinned muscle fibers J Gen Physiol Articles The effect of Mg on Ca movement between the sarcoplasmic reticulum (SR) and myofilament space (MFS) was studied in skinned muscle fibers by using isometric force as an indicator of MFS Ca. In Ca-loaded fibers at 20 degrees C, the large force spike induced by Ca in 1 mM Mg (5 mM ATP) was strongly inhibited in 3 mM Mg, and force development was extremely slow. After a brief Ca stimulus in 1 mM Mg, relaxation in Ca-free solution was significantly faster in 3 mM Mg. These changes were due to altered Ca movements, since the effect of 3 mM Mg on steady force in CaEGTA solutions was small. Changes in Mg alone induced force transients apparently due to altered Ca movement. In relaxed fibers, decreasing the Mg to 0.25 mM caused phasic force development. In contracting fibers in Ca solutions, increasing the Mg caused a large transient relaxation. The effects of increased Mg were antagonized by 0.5 mM Cd, an inhibitor of the SR Ca transport system. The results indicate that active Ca uptake by the SR in situ is stimulated by Mg, and that it can affect local MFS [Ca++] in the presence of a substantial Ca source. These results provide evidence that an increased rate of Ca uptake in 3 mM Mg could account for inhibition of the large force spike associated with Ca-induced Ca release in skinned fibers. The Rockefeller University Press 1977-01-01 /pmc/articles/PMC2215045/ /pubmed/299886 Text en 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 | Articles Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title | Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title_full | Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title_fullStr | Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title_full_unstemmed | Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title_short | Regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
title_sort | regulation by magnesium of intracellular calcium movement in skinned muscle fibers |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215045/ https://www.ncbi.nlm.nih.gov/pubmed/299886 |