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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

Changes in the resting membrane potential induced by 100 nM nicotine in rat soleus muscle in control, after 24 and 72 h of hindlimb suspensions. (a) RMPs were measured in the same muscles prior to (white columns) and after 60 min of nicotine application (grey columns); 12 muscles, control, 4 muscles, after 24 h and 8 muscles after 72 h of HS; in separate muscles RMPs were measured after 30 min of 100 nM ouabain application (cross hatched columns) and in the presence of ouabain after 60 min of nicotine application (black columns). 4 muscles, control, 4 muscles, after 24 h of HS. **P < 0.01 compared to RMPs before nicotine's addition. (b) the effect of ouabain (30 min incubation) on the RMPs of control rat soleus muscles. Columns show mean data from 4 to 6 different muscles.
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fig4: Changes in the resting membrane potential induced by 100 nM nicotine in rat soleus muscle in control, after 24 and 72 h of hindlimb suspensions. (a) RMPs were measured in the same muscles prior to (white columns) and after 60 min of nicotine application (grey columns); 12 muscles, control, 4 muscles, after 24 h and 8 muscles after 72 h of HS; in separate muscles RMPs were measured after 30 min of 100 nM ouabain application (cross hatched columns) and in the presence of ouabain after 60 min of nicotine application (black columns). 4 muscles, control, 4 muscles, after 24 h of HS. **P < 0.01 compared to RMPs before nicotine's addition. (b) the effect of ouabain (30 min incubation) on the RMPs of control rat soleus muscles. Columns show mean data from 4 to 6 different muscles.

Mentions: Upon 60 min exposure of muscles to 100 nM nicotine, a small but significant (P < 0.01) depolarization was detected (not shown), as expected if nicotine initially opens a small number of nAChRs. This depolarization was followed by sustained hyperpolarization of 2.7 ± 0.6 mV (P < 0.01; 12 muscles) (Figure 4(a)). After 24 or 72 h of HS, the RMPs depolarized as indicated above; however the stimulation of Na,K-ATPase activity by nicotine remained (Figure 4(a)), indicating the continued presence of functional Na,K-ATPase in the sarcolemma.


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)

Changes in the resting membrane potential induced by 100 nM nicotine in rat soleus muscle in control, after 24 and 72 h of hindlimb suspensions. (a) RMPs were measured in the same muscles prior to (white columns) and after 60 min of nicotine application (grey columns); 12 muscles, control, 4 muscles, after 24 h and 8 muscles after 72 h of HS; in separate muscles RMPs were measured after 30 min of 100 nM ouabain application (cross hatched columns) and in the presence of ouabain after 60 min of nicotine application (black columns). 4 muscles, control, 4 muscles, after 24 h of HS. **P < 0.01 compared to RMPs before nicotine's addition. (b) the effect of ouabain (30 min incubation) on the RMPs of control rat soleus muscles. Columns show mean data from 4 to 6 different muscles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: Changes in the resting membrane potential induced by 100 nM nicotine in rat soleus muscle in control, after 24 and 72 h of hindlimb suspensions. (a) RMPs were measured in the same muscles prior to (white columns) and after 60 min of nicotine application (grey columns); 12 muscles, control, 4 muscles, after 24 h and 8 muscles after 72 h of HS; in separate muscles RMPs were measured after 30 min of 100 nM ouabain application (cross hatched columns) and in the presence of ouabain after 60 min of nicotine application (black columns). 4 muscles, control, 4 muscles, after 24 h of HS. **P < 0.01 compared to RMPs before nicotine's addition. (b) the effect of ouabain (30 min incubation) on the RMPs of control rat soleus muscles. Columns show mean data from 4 to 6 different muscles.
Mentions: Upon 60 min exposure of muscles to 100 nM nicotine, a small but significant (P < 0.01) depolarization was detected (not shown), as expected if nicotine initially opens a small number of nAChRs. This depolarization was followed by sustained hyperpolarization of 2.7 ± 0.6 mV (P < 0.01; 12 muscles) (Figure 4(a)). After 24 or 72 h of HS, the RMPs depolarized as indicated above; however the stimulation of Na,K-ATPase activity by nicotine remained (Figure 4(a)), indicating the continued presence of functional Na,K-ATPase in the sarcolemma.

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