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Isoform-specific Na,K-ATPase alterations precede disuse-induced atrophy of rat soleus muscle.

Kravtsova VV, Matchkov VV, Bouzinova EV, Vasiliev AN, Razgovorova IA, Heiny JA, Krivoi II - Biomed Res Int (2015)

Bottom Line: Our results indicate that 24-72 h of HS specifically decreases the electrogenic activity of the Na,K-ATPase α2 isozyme and the RMP of soleus muscle fibers.This decrease occurs prior to muscle atrophy or any change in contractile parameters.The α1 Na,K-ATPase electrogenic activity, protein and mRNA content did not change.

View Article: PubMed Central - PubMed

Affiliation: St. Petersburg State University, 7/9 University emb., St. Petersburg 199034, Russia.

ABSTRACT
This study examines the isoform-specific effects of short-term hindlimb suspension (HS) on the Na,K-ATPase in rat soleus muscle. Rats were exposed to 24-72 h of HS and we analyzed the consequences on soleus muscle mass and contractile parameters; excitability and the resting membrane potential (RMP) of muscle fibers; the electrogenic activity, protein, and mRNA content of the α1 and α2 Na,K-ATPase; the functional activity and plasma membrane localization of the α2 Na,K-ATPase. Our results indicate that 24-72 h of HS specifically decreases the electrogenic activity of the Na,K-ATPase α2 isozyme and the RMP of soleus muscle fibers. This decrease occurs prior to muscle atrophy or any change in contractile parameters. The α2 mRNA and protein content increased after 24 h of HS and returned to initial levels at 72 h; however, even the increased content was not able to restore α2 enzyme activity in the disused soleus muscle. There was no change in the membrane localization of α2 Na,K-ATPase. The α1 Na,K-ATPase electrogenic activity, protein and mRNA content did not change. Our findings suggest that skeletal muscle use is absolutely required for α2 Na,K-ATPase transport activity and provide the first evidence that Na,K-ATPase alterations precede HS-induced muscle atrophy.

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Related in: MedlinePlus

Hindlimb suspension decreases excitability and alters electrogenesis of rat soleus muscle. (a) force-voltage relationships of twitch tensions in control soleus muscles (open circles, n = 18), after 24 h (closed circles, n = 15) and 72 h (triangles, n = 8) of HS. Force-voltage relationships were determined using 1 ms stimuli (direct stimulation) of increasing voltage to elicit maximum force of twitch tension. % to force obtained at supramaximal stimulation is shown. Insert-expanded curve for voltages below 10 mV; points that significantly differ from corresponding control points are marked by asterix. (b) The resting membrane potential (white columns) and total electrogenic activity of the Na,K-ATPase (black columns) in control soleus muscles and after 24 h and 72 h of HS. *P < 0.05; **P < 0.01 compared to respective control.
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fig2: Hindlimb suspension decreases excitability and alters electrogenesis of rat soleus muscle. (a) force-voltage relationships of twitch tensions in control soleus muscles (open circles, n = 18), after 24 h (closed circles, n = 15) and 72 h (triangles, n = 8) of HS. Force-voltage relationships were determined using 1 ms stimuli (direct stimulation) of increasing voltage to elicit maximum force of twitch tension. % to force obtained at supramaximal stimulation is shown. Insert-expanded curve for voltages below 10 mV; points that significantly differ from corresponding control points are marked by asterix. (b) The resting membrane potential (white columns) and total electrogenic activity of the Na,K-ATPase (black columns) in control soleus muscles and after 24 h and 72 h of HS. *P < 0.05; **P < 0.01 compared to respective control.

Mentions: 24–72 h of HS significantly shifted the initial part of the force-voltage relationship to higher voltages, suggesting decreased excitability (Figure 2(a)). Over the same period, 24 h of HS depolarized the RMPs of extrajunctional membrane regions from −73.7 ± 0.4 mV (10 muscles, 211 fibers) in control muscles to −71.2 ± 0.3 mV (12 muscles, 269 fibers), and this value remained unchanged (−70.2 ± 0.6 mV; 8 muscles, 126 fibers) up to 72 h of HS (Figure 2(b)).


Isoform-specific Na,K-ATPase alterations precede disuse-induced atrophy of rat soleus muscle.

Kravtsova VV, Matchkov VV, Bouzinova EV, Vasiliev AN, Razgovorova IA, Heiny JA, Krivoi II - Biomed Res Int (2015)

Hindlimb suspension decreases excitability and alters electrogenesis of rat soleus muscle. (a) force-voltage relationships of twitch tensions in control soleus muscles (open circles, n = 18), after 24 h (closed circles, n = 15) and 72 h (triangles, n = 8) of HS. Force-voltage relationships were determined using 1 ms stimuli (direct stimulation) of increasing voltage to elicit maximum force of twitch tension. % to force obtained at supramaximal stimulation is shown. Insert-expanded curve for voltages below 10 mV; points that significantly differ from corresponding control points are marked by asterix. (b) The resting membrane potential (white columns) and total electrogenic activity of the Na,K-ATPase (black columns) in control soleus muscles and after 24 h and 72 h of HS. *P < 0.05; **P < 0.01 compared to respective control.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4309216&req=5

fig2: Hindlimb suspension decreases excitability and alters electrogenesis of rat soleus muscle. (a) force-voltage relationships of twitch tensions in control soleus muscles (open circles, n = 18), after 24 h (closed circles, n = 15) and 72 h (triangles, n = 8) of HS. Force-voltage relationships were determined using 1 ms stimuli (direct stimulation) of increasing voltage to elicit maximum force of twitch tension. % to force obtained at supramaximal stimulation is shown. Insert-expanded curve for voltages below 10 mV; points that significantly differ from corresponding control points are marked by asterix. (b) The resting membrane potential (white columns) and total electrogenic activity of the Na,K-ATPase (black columns) in control soleus muscles and after 24 h and 72 h of HS. *P < 0.05; **P < 0.01 compared to respective control.
Mentions: 24–72 h of HS significantly shifted the initial part of the force-voltage relationship to higher voltages, suggesting decreased excitability (Figure 2(a)). Over the same period, 24 h of HS depolarized the RMPs of extrajunctional membrane regions from −73.7 ± 0.4 mV (10 muscles, 211 fibers) in control muscles to −71.2 ± 0.3 mV (12 muscles, 269 fibers), and this value remained unchanged (−70.2 ± 0.6 mV; 8 muscles, 126 fibers) up to 72 h of HS (Figure 2(b)).

Bottom Line: Our results indicate that 24-72 h of HS specifically decreases the electrogenic activity of the Na,K-ATPase α2 isozyme and the RMP of soleus muscle fibers.This decrease occurs prior to muscle atrophy or any change in contractile parameters.The α1 Na,K-ATPase electrogenic activity, protein and mRNA content did not change.

View Article: PubMed Central - PubMed

Affiliation: St. Petersburg State University, 7/9 University emb., St. Petersburg 199034, Russia.

ABSTRACT
This study examines the isoform-specific effects of short-term hindlimb suspension (HS) on the Na,K-ATPase in rat soleus muscle. Rats were exposed to 24-72 h of HS and we analyzed the consequences on soleus muscle mass and contractile parameters; excitability and the resting membrane potential (RMP) of muscle fibers; the electrogenic activity, protein, and mRNA content of the α1 and α2 Na,K-ATPase; the functional activity and plasma membrane localization of the α2 Na,K-ATPase. Our results indicate that 24-72 h of HS specifically decreases the electrogenic activity of the Na,K-ATPase α2 isozyme and the RMP of soleus muscle fibers. This decrease occurs prior to muscle atrophy or any change in contractile parameters. The α2 mRNA and protein content increased after 24 h of HS and returned to initial levels at 72 h; however, even the increased content was not able to restore α2 enzyme activity in the disused soleus muscle. There was no change in the membrane localization of α2 Na,K-ATPase. The α1 Na,K-ATPase electrogenic activity, protein and mRNA content did not change. Our findings suggest that skeletal muscle use is absolutely required for α2 Na,K-ATPase transport activity and provide the first evidence that Na,K-ATPase alterations precede HS-induced muscle atrophy.

Show MeSH
Related in: MedlinePlus