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Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps
The general working hypothesis of this study was that muscle fatigue and force recovery depend on passive and active fluxes of Na(+) and K(+). This is tested by examining the time-course of excitation-induced fluxes of Na(+) and K(+) during 5–300 sec of 10–60 Hz continuous electrical stimulation in...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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BlackWell Publishing Ltd
2015
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425977/ https://www.ncbi.nlm.nih.gov/pubmed/25862098 http://dx.doi.org/10.14814/phy2.12373 |
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author | Clausen, Torben |
author_facet | Clausen, Torben |
author_sort | Clausen, Torben |
collection | PubMed |
description | The general working hypothesis of this study was that muscle fatigue and force recovery depend on passive and active fluxes of Na(+) and K(+). This is tested by examining the time-course of excitation-induced fluxes of Na(+) and K(+) during 5–300 sec of 10–60 Hz continuous electrical stimulation in rat extensor digitorum longus (EDL) muscles in vitro and in vivo using (22)Na and flame photometric determination of Na(+) and K(+). 60 sec of 60 Hz stimulation rapidly increases (22)Na influx, during the initial phase (0–15 sec) by 0.53 μmol(sec)(−1)(g wet wt.)(−1), sixfold faster than in the later phase (15–60 sec). These values agree with flame photometric measurements of Na(+) content. The progressive reduction in the rate of excitation-induced Na(+) uptake is likely to reflect gradual loss of excitability due to accumulation of K(+) in the extracellular space and t-tubules leading to depolarization. This is in keeping with the concomitant progressive loss of contractile force previously demonstrated. During electrical stimulation rat muscles rapidly reach high rates of active Na(+), K(+)-transport (in EDL muscles a sevenfold increase and in soleus muscles a 22-fold increase), allowing efficient and selective compensation for the large excitation-induced passive Na(+), K(+)-fluxes demonstrated over the latest decades. The excitation-induced changes in passive fluxes of Na(+) and K(+) are both clearly larger than previously observed. The excitation-induced reduction in [Na(+)](o) contributes considerably to the inhibitory effect of elevated [K(+)](o). In conclusion, excitation-induced passive and active Na(+) and K(+) fluxes are important causes of muscle fatigue and force recovery, respectively. |
format | Online Article Text |
id | pubmed-4425977 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | BlackWell Publishing Ltd |
record_format | MEDLINE/PubMed |
spelling | pubmed-44259772015-05-14 Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps Clausen, Torben Physiol Rep Original Research The general working hypothesis of this study was that muscle fatigue and force recovery depend on passive and active fluxes of Na(+) and K(+). This is tested by examining the time-course of excitation-induced fluxes of Na(+) and K(+) during 5–300 sec of 10–60 Hz continuous electrical stimulation in rat extensor digitorum longus (EDL) muscles in vitro and in vivo using (22)Na and flame photometric determination of Na(+) and K(+). 60 sec of 60 Hz stimulation rapidly increases (22)Na influx, during the initial phase (0–15 sec) by 0.53 μmol(sec)(−1)(g wet wt.)(−1), sixfold faster than in the later phase (15–60 sec). These values agree with flame photometric measurements of Na(+) content. The progressive reduction in the rate of excitation-induced Na(+) uptake is likely to reflect gradual loss of excitability due to accumulation of K(+) in the extracellular space and t-tubules leading to depolarization. This is in keeping with the concomitant progressive loss of contractile force previously demonstrated. During electrical stimulation rat muscles rapidly reach high rates of active Na(+), K(+)-transport (in EDL muscles a sevenfold increase and in soleus muscles a 22-fold increase), allowing efficient and selective compensation for the large excitation-induced passive Na(+), K(+)-fluxes demonstrated over the latest decades. The excitation-induced changes in passive fluxes of Na(+) and K(+) are both clearly larger than previously observed. The excitation-induced reduction in [Na(+)](o) contributes considerably to the inhibitory effect of elevated [K(+)](o). In conclusion, excitation-induced passive and active Na(+) and K(+) fluxes are important causes of muscle fatigue and force recovery, respectively. BlackWell Publishing Ltd 2015-04-12 /pmc/articles/PMC4425977/ /pubmed/25862098 http://dx.doi.org/10.14814/phy2.12373 Text en © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society. http://creativecommons.org/licenses/by/4.0/ This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Original Research Clausen, Torben Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title | Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title_full | Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title_fullStr | Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title_full_unstemmed | Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title_short | Excitation of skeletal muscle is a self-limiting process, due to run-down of Na(+), K(+) gradients, recoverable by stimulation of the Na(+), K(+) pumps |
title_sort | excitation of skeletal muscle is a self-limiting process, due to run-down of na(+), k(+) gradients, recoverable by stimulation of the na(+), k(+) pumps |
topic | Original Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425977/ https://www.ncbi.nlm.nih.gov/pubmed/25862098 http://dx.doi.org/10.14814/phy2.12373 |
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