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Casted-immobilization downregulates glucocorticoid receptor expression in rat slow-twitch soleus muscle.

Authors: Sato, S  Suzuki, H  Tsujimoto, H  Shirato, K  Tachiyashiki, K  Imaizumi, K 
Citation: Sato S, etal., Life Sci. 2011 Dec 19;89(25-26):962-7. Epub 2011 Oct 20.
Pubmed: (View Article at PubMed) PMID:22036623
DOI: Full-text: DOI:10.1016/j.lfs.2011.10.008

AIMS: Glucocorticoids bind to the glucocorticoid receptor (GR) and increase catabolism of muscle proteins via the ubiquitin-proteasome pathway. Activation of beta(2)-adrenergic receptor (beta(2)-AR) in skeletal muscle has been shown to induce muscle hypertrophy by promoting muscle protein synthesis and/or attenuating protein degradation. The aim of this study was to investigate the correlation between disuse-induced muscle atrophy, and expression of GR and beta(2)-AR. METHODS: Rats were subjected to casted-immobilization (knee and foot arthrodesis), a model for muscle disuse, for 10 days. Fast-twitch (extensor digitorum longus: EDL) and slow-twitch (soleus: SOL) muscles were isolated and subsequently used for analysis. The expression of GR and beta(2)-AR was analyzed by real-time RT-PCR and western blotting. In addition, we analyzed plasma catecholamine and corticosterone concentrations by ELISA. KEY FINDINGS: Casted-immobilization-induced muscle atrophy was much greater in the SOL muscle than in the EDL muscle. Casted-immobilization decreased the expression of GR mRNA and protein in the SOL muscle but not in the EDL muscle. Although the expression of beta(2)-AR protein in the cytosol and membrane-rich fractions was not changed by casted-immobilization in either muscle, casted-immobilization decreased the expression of beta(2)-AR mRNA in the SOL muscle. Plasma catecholamine and corticosterone concentrations, however, were largely unaffected by casted-immobilization during the experimental period. SIGNIFICANCE: This study provides evidence that casted-immobilization-induced muscle disuse downregulates GR expression in slow-twitch muscle. These results suggest that muscle disuse suppresses glucocorticoid signals, such as muscle protein breakdown and transcription of the beta(2)-AR gene, via downregulation of GR expression in slow-twitch muscle.


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RGD Object Information
RGD ID: 5686283
Created: 2012-01-18
Species: All species
Last Modified: 2012-01-18
Status: ACTIVE


RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.