Limits...
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.

Show MeSH

Related in: MedlinePlus

24–72 h of hindlimb suspension specifically alters the electrogenic activity (a) and the relative mRNA (b) and protein (c) contents of the α2 Na,K-ATPase in rat soleus muscle. α1 and α2 Na,K-ATPase, white and black columns, respectively. (a) Na,K-ATPase α1 and α2 electrogenic activity computed as the difference in resting potential measured before and after blockade of the Na,K-ATPase isozymes by ouabain. (b) and (c) data normalized to the average level of expression under control conditions. Upper panels (c) show representative immunoblots. Columns show mean data from 5 to 10 different muscle samples (panel (b)) and 10 different muscle samples (panel (c)). **P < 0.01 compare to control.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4309216&req=5

fig3: 24–72 h of hindlimb suspension specifically alters the electrogenic activity (a) and the relative mRNA (b) and protein (c) contents of the α2 Na,K-ATPase in rat soleus muscle. α1 and α2 Na,K-ATPase, white and black columns, respectively. (a) Na,K-ATPase α1 and α2 electrogenic activity computed as the difference in resting potential measured before and after blockade of the Na,K-ATPase isozymes by ouabain. (b) and (c) data normalized to the average level of expression under control conditions. Upper panels (c) show representative immunoblots. Columns show mean data from 5 to 10 different muscle samples (panel (b)) and 10 different muscle samples (panel (c)). **P < 0.01 compare to control.

Mentions: In control muscles, electrogenic transport by the α1 and α2 Na,K-ATPase isozymes contributes −8.4 ± 0.7 mV and −3.2 ± 0.7 mV (6 muscles), respectively, to the RMP. HS alters these contributions in an isoform-specific manner. After 24 h of HS, the electrogenic potential contributed by α1 isozyme remains unchanged, while the contribution of α2 isozyme decreased dramatically to only −0.9 ± 0.6 mV (6 muscles; P < 0.01) (Figure 3(a)). The lower activity of α2 isozyme remained for up to 72 h of HS while the contribution of α1 isozyme was not significantly different from control value (Figure 3(a)). Therefore, the HS-induced membrane depolarization is due to a specific decrease in the activity of the α2 isozyme.


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)

24–72 h of hindlimb suspension specifically alters the electrogenic activity (a) and the relative mRNA (b) and protein (c) contents of the α2 Na,K-ATPase in rat soleus muscle. α1 and α2 Na,K-ATPase, white and black columns, respectively. (a) Na,K-ATPase α1 and α2 electrogenic activity computed as the difference in resting potential measured before and after blockade of the Na,K-ATPase isozymes by ouabain. (b) and (c) data normalized to the average level of expression under control conditions. Upper panels (c) show representative immunoblots. Columns show mean data from 5 to 10 different muscle samples (panel (b)) and 10 different muscle samples (panel (c)). **P < 0.01 compare to control.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig3: 24–72 h of hindlimb suspension specifically alters the electrogenic activity (a) and the relative mRNA (b) and protein (c) contents of the α2 Na,K-ATPase in rat soleus muscle. α1 and α2 Na,K-ATPase, white and black columns, respectively. (a) Na,K-ATPase α1 and α2 electrogenic activity computed as the difference in resting potential measured before and after blockade of the Na,K-ATPase isozymes by ouabain. (b) and (c) data normalized to the average level of expression under control conditions. Upper panels (c) show representative immunoblots. Columns show mean data from 5 to 10 different muscle samples (panel (b)) and 10 different muscle samples (panel (c)). **P < 0.01 compare to control.
Mentions: In control muscles, electrogenic transport by the α1 and α2 Na,K-ATPase isozymes contributes −8.4 ± 0.7 mV and −3.2 ± 0.7 mV (6 muscles), respectively, to the RMP. HS alters these contributions in an isoform-specific manner. After 24 h of HS, the electrogenic potential contributed by α1 isozyme remains unchanged, while the contribution of α2 isozyme decreased dramatically to only −0.9 ± 0.6 mV (6 muscles; P < 0.01) (Figure 3(a)). The lower activity of α2 isozyme remained for up to 72 h of HS while the contribution of α1 isozyme was not significantly different from control value (Figure 3(a)). Therefore, the HS-induced membrane depolarization is due to a specific decrease in the activity of the α2 isozyme.

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