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Staircase in mammalian muscle without light chain phosphorylation
D E Rassier1, L A Tubman, B R MacIntosh
1Human Performance Laboratory, University of Calgary, Alberta, Canada.
Summary
Restoring the staircase response in atrophied skeletal muscle is possible with dantrolene sodium, even without myosin light chain phosphorylation. This suggests a novel therapeutic approach for muscle disuse atrophy.
Area of Science:
- Skeletal Muscle Physiology
- Muscle Atrophy Research
- Pharmacology
Background:
- Disuse-atrophied skeletal muscle exhibits an absent staircase response and reduced myosin light chain phosphorylation.
- Enhanced calcium release is implicated in the altered contractile properties of atrophied muscle.
Purpose of the Study:
- To investigate if the staircase response can be restored in atrophied muscle.
- To determine if this restoration is possible independently of myosin light chain phosphorylation.
- To explore the role of enhanced calcium release in this phenomenon.
Main Methods:
- Utilized a rat model of skeletal muscle disuse atrophy induced by tetrodotoxin (TTX).
- Administered dantrolene sodium (DS), a calcium release inhibitor, to control, sham, and TTX-treated rats.
- Assessed in situ isometric contractile responses and regulatory light chain (R-LC) phosphorylation.
Main Results:
- Dantrolene sodium treatment enabled a positive staircase response in both atrophied and control muscles.
- The restoration of the staircase response occurred despite significantly lower R-LC phosphorylation in atrophied muscles.
- DS attenuated active force but subsequent stimulation revealed the staircase effect.
Conclusions:
- Dantrolene sodium can restore the staircase response in disuse-atrophied skeletal muscle.
- This restoration appears to be independent of myosin light chain phosphorylation.
- Reducing enhanced calcium release is a key mechanism for recovering contractile function in atrophied muscle.