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Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse

The diaphragm muscle of hyperkalemic periodic paralysis (HyperKPP) patients and of the M1592V HyperKPP mouse model rarely suffers from the myotonic and paralytic symptoms that occur in limb muscles. Enigmatically, HyperKPP diaphragm expresses the mutant NaV1.4 channel and, more importantly, has an a...

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Autores principales: Ammar, Tarek, Lin, Wei, Higgins, Amanda, Hayward, Lawrence J., Renaud, Jean-Marc
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4664826/
https://www.ncbi.nlm.nih.gov/pubmed/26621775
http://dx.doi.org/10.1085/jgp.201511476
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author Ammar, Tarek
Lin, Wei
Higgins, Amanda
Hayward, Lawrence J.
Renaud, Jean-Marc
author_facet Ammar, Tarek
Lin, Wei
Higgins, Amanda
Hayward, Lawrence J.
Renaud, Jean-Marc
author_sort Ammar, Tarek
collection PubMed
description The diaphragm muscle of hyperkalemic periodic paralysis (HyperKPP) patients and of the M1592V HyperKPP mouse model rarely suffers from the myotonic and paralytic symptoms that occur in limb muscles. Enigmatically, HyperKPP diaphragm expresses the mutant NaV1.4 channel and, more importantly, has an abnormally high Na(+) influx similar to that in extensor digitorum longus (EDL) and soleus, two hindlimb muscles suffering from the robust HyperKPP abnormalities. The objective was to uncover the physiological mechanisms that render HyperKPP diaphragm asymptomatic. A first mechanism involves efficient maintenance of resting membrane polarization in HyperKPP diaphragm at various extracellular K(+) concentrations compared with larger membrane depolarizations in HyperKPP EDL and soleus. The improved resting membrane potential (EM) results from significantly increased Na(+) K(+) pump electrogenic activity, and not from an increased protein content. Action potential amplitude was greater in HyperKPP diaphragm than in HyperKPP soleus and EDL, providing a second mechanism for the asymptomatic behavior of the HyperKPP diaphragm. One suggested mechanism for the greater action potential amplitude is lower intracellular Na(+) concentration because of greater Na(+) K(+) pump activity, allowing better Na(+) current during the action potential depolarization phase. Finally, HyperKPP diaphragm had a greater capacity to generate force at depolarized EM compared with wild-type diaphragm. Action potential amplitude was not different between wild-type and HyperKPP diaphragm. There was also no evidence for an increased activity of the Na(+)–Ca(2+) exchanger working in the reverse mode in the HyperKPP diaphragm compared with the wild-type diaphragm. So, a third mechanism remains to be elucidated to fully understand how HyperKPP diaphragm generates more force compared with wild type. Although the mechanism for the greater force at depolarized resting EM remains to be determined, this study provides support for the modulation of the Na(+) K(+) pump as a component of therapy to alleviate weakness in HyperKPP.
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spelling pubmed-46648262016-06-01 Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse Ammar, Tarek Lin, Wei Higgins, Amanda Hayward, Lawrence J. Renaud, Jean-Marc J Gen Physiol Research Articles The diaphragm muscle of hyperkalemic periodic paralysis (HyperKPP) patients and of the M1592V HyperKPP mouse model rarely suffers from the myotonic and paralytic symptoms that occur in limb muscles. Enigmatically, HyperKPP diaphragm expresses the mutant NaV1.4 channel and, more importantly, has an abnormally high Na(+) influx similar to that in extensor digitorum longus (EDL) and soleus, two hindlimb muscles suffering from the robust HyperKPP abnormalities. The objective was to uncover the physiological mechanisms that render HyperKPP diaphragm asymptomatic. A first mechanism involves efficient maintenance of resting membrane polarization in HyperKPP diaphragm at various extracellular K(+) concentrations compared with larger membrane depolarizations in HyperKPP EDL and soleus. The improved resting membrane potential (EM) results from significantly increased Na(+) K(+) pump electrogenic activity, and not from an increased protein content. Action potential amplitude was greater in HyperKPP diaphragm than in HyperKPP soleus and EDL, providing a second mechanism for the asymptomatic behavior of the HyperKPP diaphragm. One suggested mechanism for the greater action potential amplitude is lower intracellular Na(+) concentration because of greater Na(+) K(+) pump activity, allowing better Na(+) current during the action potential depolarization phase. Finally, HyperKPP diaphragm had a greater capacity to generate force at depolarized EM compared with wild-type diaphragm. Action potential amplitude was not different between wild-type and HyperKPP diaphragm. There was also no evidence for an increased activity of the Na(+)–Ca(2+) exchanger working in the reverse mode in the HyperKPP diaphragm compared with the wild-type diaphragm. So, a third mechanism remains to be elucidated to fully understand how HyperKPP diaphragm generates more force compared with wild type. Although the mechanism for the greater force at depolarized resting EM remains to be determined, this study provides support for the modulation of the Na(+) K(+) pump as a component of therapy to alleviate weakness in HyperKPP. The Rockefeller University Press 2015-12 /pmc/articles/PMC4664826/ /pubmed/26621775 http://dx.doi.org/10.1085/jgp.201511476 Text en © 2015 Ammar et al. 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 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
spellingShingle Research Articles
Ammar, Tarek
Lin, Wei
Higgins, Amanda
Hayward, Lawrence J.
Renaud, Jean-Marc
Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title_full Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title_fullStr Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title_full_unstemmed Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title_short Understanding the physiology of the asymptomatic diaphragm of the M1592V hyperkalemic periodic paralysis mouse
title_sort understanding the physiology of the asymptomatic diaphragm of the m1592v hyperkalemic periodic paralysis mouse
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4664826/
https://www.ncbi.nlm.nih.gov/pubmed/26621775
http://dx.doi.org/10.1085/jgp.201511476
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