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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 does not alter the membrane localization of α2 Na,K-ATPase. A rat soleus muscle was labeled with bodipy-conjugated ouabain (1 μM) ((A), (B)) or with specific antibodies ((C), (D)) to label the α2 Na,K-ATPase. (A), (C) control; (B) after 24 h HS and (D) after 72 h of HS. Scale bars: 25 μm.
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fig5: Hindlimb suspension does not alter the membrane localization of α2 Na,K-ATPase. A rat soleus muscle was labeled with bodipy-conjugated ouabain (1 μM) ((A), (B)) or with specific antibodies ((C), (D)) to label the α2 Na,K-ATPase. (A), (C) control; (B) after 24 h HS and (D) after 72 h of HS. Scale bars: 25 μm.

Mentions: It is also possible that HS may alter the localization of α2 Na,K-ATPase in the sarcolemma and thereby alter its electrogenic activity. We investigated this possibility by imaging the intact m. soleus labeled with a fluorescent, specific ligand of the Na,K-ATPase (bodipy-conjugated ouabain, 1 μM) [25, 28]. The α2 Na,K-ATPase isozyme is present on the sarcolemma and transverse tubule membranes [30]. Consistent with this observation, the fluorescent ouabain signal is detected as double rows of label with a repeat pattern of two per sarcomere, as expected from the dual transverse-tubule openings at the A-I junctions of mammalian muscle [25, 28] (Figure 5(A)). 24 h of HS did not alter the extrajunctional localization of the Na,K-ATPase α2 isozyme (Figure 5(B)). Muscles labeled with α2 Na,K-ATPase antibody demonstrate the same result after 72 h of HS (Figures 5(C) and 5(D)).


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 does not alter the membrane localization of α2 Na,K-ATPase. A rat soleus muscle was labeled with bodipy-conjugated ouabain (1 μM) ((A), (B)) or with specific antibodies ((C), (D)) to label the α2 Na,K-ATPase. (A), (C) control; (B) after 24 h HS and (D) after 72 h of HS. Scale bars: 25 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Hindlimb suspension does not alter the membrane localization of α2 Na,K-ATPase. A rat soleus muscle was labeled with bodipy-conjugated ouabain (1 μM) ((A), (B)) or with specific antibodies ((C), (D)) to label the α2 Na,K-ATPase. (A), (C) control; (B) after 24 h HS and (D) after 72 h of HS. Scale bars: 25 μm.
Mentions: It is also possible that HS may alter the localization of α2 Na,K-ATPase in the sarcolemma and thereby alter its electrogenic activity. We investigated this possibility by imaging the intact m. soleus labeled with a fluorescent, specific ligand of the Na,K-ATPase (bodipy-conjugated ouabain, 1 μM) [25, 28]. The α2 Na,K-ATPase isozyme is present on the sarcolemma and transverse tubule membranes [30]. Consistent with this observation, the fluorescent ouabain signal is detected as double rows of label with a repeat pattern of two per sarcomere, as expected from the dual transverse-tubule openings at the A-I junctions of mammalian muscle [25, 28] (Figure 5(A)). 24 h of HS did not alter the extrajunctional localization of the Na,K-ATPase α2 isozyme (Figure 5(B)). Muscles labeled with α2 Na,K-ATPase antibody demonstrate the same result after 72 h of HS (Figures 5(C) and 5(D)).

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