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

Ammar T, Lin W, Higgins A, Hayward LJ, Renaud JM - J. Gen. Physiol. (2015)

Bottom Line: The improved resting membrane potential (EM) results from significantly increased Na(+) K(+) pump electrogenic activity, and not from an increased protein content.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.

No MeSH data available.


Related in: MedlinePlus

Tetanic force versus resting EM relationships. (A–C) Relationships were made by first expressing all mean tetanic forces of wild-type and HyperKPP muscles at various [K+]e as a percentage of the mean tetanic force of wild-type muscles at 4.7 mM K+ (taken as the normal maximum force these muscles can generate), and then plotting the relative values against the resting EM shown in Fig. 2. The numbers beside each symbol indicate the [K+]e at which tetanic force and resting EM were measured. The curves were plotted after fitting the data points to the following sigmoidal relationship:  where a, b, c, and d are constants.
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fig5: Tetanic force versus resting EM relationships. (A–C) Relationships were made by first expressing all mean tetanic forces of wild-type and HyperKPP muscles at various [K+]e as a percentage of the mean tetanic force of wild-type muscles at 4.7 mM K+ (taken as the normal maximum force these muscles can generate), and then plotting the relative values against the resting EM shown in Fig. 2. The numbers beside each symbol indicate the [K+]e at which tetanic force and resting EM were measured. The curves were plotted after fitting the data points to the following sigmoidal relationship: where a, b, c, and d are constants.

Mentions: Next, we ascertained how much of the lower forces in HyperKPP EDL and soleus and the conservation of force in the HyperKPP diaphragm are related to resting EM. To do this, we took into consideration that the tetanic force from a whole muscle is a function of the mean resting EM of all fibers, as reported previously (Renaud and Light, 1992; Cairns et al., 1997). To construct a tetanic force–resting EM relationship, we calculated all mean absolute forces at different [K+]e as a percentage of the force generated by wild-type muscles at 4.7 mM K+. The force generated by HyperKPP soleus at 4.7 and 9 mM K+ fell very close to the tetanic force–resting EM of wild-type soleus, suggesting that the lower tetanic forces of HyperKPP soleus at those [K+]e are largely caused by less negative mean resting EM (Fig. 5 A). Interestingly, although tetanic force in wild-type soleus is expected to reach zero at −54 mV, HyperKPP soleus still generated some force between −55 and −49 mV.


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

Ammar T, Lin W, Higgins A, Hayward LJ, Renaud JM - J. Gen. Physiol. (2015)

Tetanic force versus resting EM relationships. (A–C) Relationships were made by first expressing all mean tetanic forces of wild-type and HyperKPP muscles at various [K+]e as a percentage of the mean tetanic force of wild-type muscles at 4.7 mM K+ (taken as the normal maximum force these muscles can generate), and then plotting the relative values against the resting EM shown in Fig. 2. The numbers beside each symbol indicate the [K+]e at which tetanic force and resting EM were measured. The curves were plotted after fitting the data points to the following sigmoidal relationship:  where a, b, c, and d are constants.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4664826&req=5

fig5: Tetanic force versus resting EM relationships. (A–C) Relationships were made by first expressing all mean tetanic forces of wild-type and HyperKPP muscles at various [K+]e as a percentage of the mean tetanic force of wild-type muscles at 4.7 mM K+ (taken as the normal maximum force these muscles can generate), and then plotting the relative values against the resting EM shown in Fig. 2. The numbers beside each symbol indicate the [K+]e at which tetanic force and resting EM were measured. The curves were plotted after fitting the data points to the following sigmoidal relationship: where a, b, c, and d are constants.
Mentions: Next, we ascertained how much of the lower forces in HyperKPP EDL and soleus and the conservation of force in the HyperKPP diaphragm are related to resting EM. To do this, we took into consideration that the tetanic force from a whole muscle is a function of the mean resting EM of all fibers, as reported previously (Renaud and Light, 1992; Cairns et al., 1997). To construct a tetanic force–resting EM relationship, we calculated all mean absolute forces at different [K+]e as a percentage of the force generated by wild-type muscles at 4.7 mM K+. The force generated by HyperKPP soleus at 4.7 and 9 mM K+ fell very close to the tetanic force–resting EM of wild-type soleus, suggesting that the lower tetanic forces of HyperKPP soleus at those [K+]e are largely caused by less negative mean resting EM (Fig. 5 A). Interestingly, although tetanic force in wild-type soleus is expected to reach zero at −54 mV, HyperKPP soleus still generated some force between −55 and −49 mV.

Bottom Line: The improved resting membrane potential (EM) results from significantly increased Na(+) K(+) pump electrogenic activity, and not from an increased protein content.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.

No MeSH data available.


Related in: MedlinePlus