Limits...
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

Action potential amplitudes were lower in HyperKPP than in wild type, soleus, and EDL but not diaphragm. Examples of action potential traces from (A) wild-type and (B) HyperKPP EDL. Numbers at the start of each trace represent the starting resting EM. SA is for the 0.3-msec-long stimulus artifact. Dashed horizontal lines represent 0 mV. Vertical and horizontal bars represent 20 mV and 1 msec, respectively. (C–E) Resting EM and action potentials were measured from fibers located at the muscle surface. Each muscle was tested at 2 or 3 [K+]e. Data from all fibers were pooled together and separated according to their resting EM in a bin of 5 mV. For each bin, resting EM and action potential amplitudes were averaged. Vertical and horizontal bars represent the SEM of action potential amplitude and resting EM, respectively (not shown if smaller than symbol). The total number of samples varied between 158 and 385 fibers from 5 to 11 muscles. *, mean action potential amplitude from HyperKPP fibers was significantly different from that of wild type; ANOVA and LSD; P < 0.05.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig12: Action potential amplitudes were lower in HyperKPP than in wild type, soleus, and EDL but not diaphragm. Examples of action potential traces from (A) wild-type and (B) HyperKPP EDL. Numbers at the start of each trace represent the starting resting EM. SA is for the 0.3-msec-long stimulus artifact. Dashed horizontal lines represent 0 mV. Vertical and horizontal bars represent 20 mV and 1 msec, respectively. (C–E) Resting EM and action potentials were measured from fibers located at the muscle surface. Each muscle was tested at 2 or 3 [K+]e. Data from all fibers were pooled together and separated according to their resting EM in a bin of 5 mV. For each bin, resting EM and action potential amplitudes were averaged. Vertical and horizontal bars represent the SEM of action potential amplitude and resting EM, respectively (not shown if smaller than symbol). The total number of samples varied between 158 and 385 fibers from 5 to 11 muscles. *, mean action potential amplitude from HyperKPP fibers was significantly different from that of wild type; ANOVA and LSD; P < 0.05.

Mentions: Next, we measured action potentials in soleus, EDL, and diaphragm fibers. In general, at 4.7 mM K+, action potentials were easily triggered in wild-type muscles, for which >95% of fibers generated an action potential upon stimulation. The situation was very different in HyperKPP soleus and EDL. At 4.7 mM K+, 30% of HyperKPP soleus fibers failed to generate an action potential upon stimulation, while 27% of HyperKPP EDL did the same. Among the excitable fibers, action potential shapes were quite similar between wild-type and HyperKPP EDL fibers when resting EM was greater than −80 mV (measured at 4.7 mM K+; Fig. 12, A and B). At less negative resting EM, such as between −55 and −75 mV (8–10 mM K+), HyperKPP EDL fibers had action potentials with lower amplitude than their wild-type counterparts. Very few fibers generated action potential below a resting EM of −55 mV (12–15 mM K+), and for those that did, the amplitude was very small.


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)

Action potential amplitudes were lower in HyperKPP than in wild type, soleus, and EDL but not diaphragm. Examples of action potential traces from (A) wild-type and (B) HyperKPP EDL. Numbers at the start of each trace represent the starting resting EM. SA is for the 0.3-msec-long stimulus artifact. Dashed horizontal lines represent 0 mV. Vertical and horizontal bars represent 20 mV and 1 msec, respectively. (C–E) Resting EM and action potentials were measured from fibers located at the muscle surface. Each muscle was tested at 2 or 3 [K+]e. Data from all fibers were pooled together and separated according to their resting EM in a bin of 5 mV. For each bin, resting EM and action potential amplitudes were averaged. Vertical and horizontal bars represent the SEM of action potential amplitude and resting EM, respectively (not shown if smaller than symbol). The total number of samples varied between 158 and 385 fibers from 5 to 11 muscles. *, mean action potential amplitude from HyperKPP fibers was significantly different from that of wild type; ANOVA and LSD; P < 0.05.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig12: Action potential amplitudes were lower in HyperKPP than in wild type, soleus, and EDL but not diaphragm. Examples of action potential traces from (A) wild-type and (B) HyperKPP EDL. Numbers at the start of each trace represent the starting resting EM. SA is for the 0.3-msec-long stimulus artifact. Dashed horizontal lines represent 0 mV. Vertical and horizontal bars represent 20 mV and 1 msec, respectively. (C–E) Resting EM and action potentials were measured from fibers located at the muscle surface. Each muscle was tested at 2 or 3 [K+]e. Data from all fibers were pooled together and separated according to their resting EM in a bin of 5 mV. For each bin, resting EM and action potential amplitudes were averaged. Vertical and horizontal bars represent the SEM of action potential amplitude and resting EM, respectively (not shown if smaller than symbol). The total number of samples varied between 158 and 385 fibers from 5 to 11 muscles. *, mean action potential amplitude from HyperKPP fibers was significantly different from that of wild type; ANOVA and LSD; P < 0.05.
Mentions: Next, we measured action potentials in soleus, EDL, and diaphragm fibers. In general, at 4.7 mM K+, action potentials were easily triggered in wild-type muscles, for which >95% of fibers generated an action potential upon stimulation. The situation was very different in HyperKPP soleus and EDL. At 4.7 mM K+, 30% of HyperKPP soleus fibers failed to generate an action potential upon stimulation, while 27% of HyperKPP EDL did the same. Among the excitable fibers, action potential shapes were quite similar between wild-type and HyperKPP EDL fibers when resting EM was greater than −80 mV (measured at 4.7 mM K+; Fig. 12, A and B). At less negative resting EM, such as between −55 and −75 mV (8–10 mM K+), HyperKPP EDL fibers had action potentials with lower amplitude than their wild-type counterparts. Very few fibers generated action potential below a resting EM of −55 mV (12–15 mM K+), and for those that did, the amplitude was very small.

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