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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

The frequency distribution of resting EM was shifted toward less negative resting EM in the HyperKPP soleus and EDL but not in the diaphragm when compared with wild-type muscles. Resting EM values were separated in a bin of 5 mV, and the number of fibers in each bin is expressed as a percentage of the total number of tested fibers. The resting EM values under each pair of bars represent the upper bound of each bin. The total number of fibers were 209–278 (A, C, and E) for 4.7 mM K+ and 68–106 at the elevated [K+]e (B, D, and F).
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fig4: The frequency distribution of resting EM was shifted toward less negative resting EM in the HyperKPP soleus and EDL but not in the diaphragm when compared with wild-type muscles. Resting EM values were separated in a bin of 5 mV, and the number of fibers in each bin is expressed as a percentage of the total number of tested fibers. The resting EM values under each pair of bars represent the upper bound of each bin. The total number of fibers were 209–278 (A, C, and E) for 4.7 mM K+ and 68–106 at the elevated [K+]e (B, D, and F).

Mentions: Resting EM varied tremendously among mammalian muscle fibers. Consequently, one cannot just use the mean resting EM to represent all fibers. The frequency distribution of resting EM was then documented by separating all measured values in bins of 5 mV. For soleus muscles, the frequency distribution for HyperKPP fibers was shifted toward less negative resting EM compared with wild-type fibers at both 4.7 and 13 mM K+ (Fig. 4, A and B). At 4.7 mM K+, 69% of all wild-type soleus fibers had a resting EM above −70 mV compared with only 21% for HyperKPP fibers. Muscles with mean resting EM of less than −55 mV lose their capacity to generate force (Renaud and Light, 1992; Cairns et al., 1997). At 4.7 mM K+, 27% of all HyperKPP soleus fibers had a resting EM below −55 mV compared with <1% for wild-type fibers. The proportion of HyperKPP soleus fibers with resting EM below −55 mV increases to 78% at 13 mM K+, whereas it increased only to 46% for wild-type fibers. A similar shift toward less negative resting EM in HyperKPP EDL fibers was also observed at 4.7 and 14 mM K+ (Fig. 4, C and D). There were, however, two major differences between HyperKPP soleus and EDL: at 4.7 mM K+, 47% of HyperKPP EDL fibers had a resting EM above −70 mV compared with only 21% for soleus fibers, whereas the proportion of fibers with a resting EM below −55 mV was just 11% for EDL compared with 27% for soleus. Contrary to hindlimb muscles, there was no major shift in the frequency distribution of resting EM between the wild-type and HyperKPP diaphragm (Fig. 4, E and F). Only small differences were observed where the number of fibers with a resting EM ranging between −65 and −75 mV was less in HyperKPP than in wild type, whereas the number of fibers with a resting EM between −55 and −60 mV was slightly higher in HyperKPP. These small differences explained the slightly less negative mean resting EM of HyperKPP fibers compared with wild-type fibers in Fig. 3 C.


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)

The frequency distribution of resting EM was shifted toward less negative resting EM in the HyperKPP soleus and EDL but not in the diaphragm when compared with wild-type muscles. Resting EM values were separated in a bin of 5 mV, and the number of fibers in each bin is expressed as a percentage of the total number of tested fibers. The resting EM values under each pair of bars represent the upper bound of each bin. The total number of fibers were 209–278 (A, C, and E) for 4.7 mM K+ and 68–106 at the elevated [K+]e (B, D, and F).
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig4: The frequency distribution of resting EM was shifted toward less negative resting EM in the HyperKPP soleus and EDL but not in the diaphragm when compared with wild-type muscles. Resting EM values were separated in a bin of 5 mV, and the number of fibers in each bin is expressed as a percentage of the total number of tested fibers. The resting EM values under each pair of bars represent the upper bound of each bin. The total number of fibers were 209–278 (A, C, and E) for 4.7 mM K+ and 68–106 at the elevated [K+]e (B, D, and F).
Mentions: Resting EM varied tremendously among mammalian muscle fibers. Consequently, one cannot just use the mean resting EM to represent all fibers. The frequency distribution of resting EM was then documented by separating all measured values in bins of 5 mV. For soleus muscles, the frequency distribution for HyperKPP fibers was shifted toward less negative resting EM compared with wild-type fibers at both 4.7 and 13 mM K+ (Fig. 4, A and B). At 4.7 mM K+, 69% of all wild-type soleus fibers had a resting EM above −70 mV compared with only 21% for HyperKPP fibers. Muscles with mean resting EM of less than −55 mV lose their capacity to generate force (Renaud and Light, 1992; Cairns et al., 1997). At 4.7 mM K+, 27% of all HyperKPP soleus fibers had a resting EM below −55 mV compared with <1% for wild-type fibers. The proportion of HyperKPP soleus fibers with resting EM below −55 mV increases to 78% at 13 mM K+, whereas it increased only to 46% for wild-type fibers. A similar shift toward less negative resting EM in HyperKPP EDL fibers was also observed at 4.7 and 14 mM K+ (Fig. 4, C and D). There were, however, two major differences between HyperKPP soleus and EDL: at 4.7 mM K+, 47% of HyperKPP EDL fibers had a resting EM above −70 mV compared with only 21% for soleus fibers, whereas the proportion of fibers with a resting EM below −55 mV was just 11% for EDL compared with 27% for soleus. Contrary to hindlimb muscles, there was no major shift in the frequency distribution of resting EM between the wild-type and HyperKPP diaphragm (Fig. 4, E and F). Only small differences were observed where the number of fibers with a resting EM ranging between −65 and −75 mV was less in HyperKPP than in wild type, whereas the number of fibers with a resting EM between −55 and −60 mV was slightly higher in HyperKPP. These small differences explained the slightly less negative mean resting EM of HyperKPP fibers compared with wild-type fibers in Fig. 3 C.

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