However, basal MuRF1, REDD1, FoxO3 and FoxO4 mRNA levels were not decreased in the GH-treated SDRs compared to the SDRs, suggesting other mechanism may regulate the Dex unresponsiveness. Dex induced muscle atrophy in soleus and EDL muscles after GH administration in the present study. The effect was observed in both type1 andtype2fibers. There are many reports that Dex stimulated muscles atrophy in EDL not but soleus muscle. In contrast, there are many reports including ours that Dex caused muscle atrophy in both EDL and soleus muscles. Consistent with the Dex��s action in EDL and soleus muscles, we found that GR mRNA levels were not different between soleus and EDL muscles. We also found that the effect of BCAA on muscle mass was not clear in SDRs. BCAA did not increase CSA of muscle fibers in SDR. This finding contrasted our previous finding that BCAA increases CSA of muscle fibers in SD rats. Furthermore, we found that, in the SDR muscles, BCAA did not stimulate the phosphorylation of p70S6K or 4E-BP1, both of which are important for enhancing protein synthesis. Additionally, the protein degradation pathway did not appear to be affected by BCAA in the SDR muscles. It has been reported that Bnip3, atrogin-1 and MuRF1 expressions are increased in a variety of types of muscle atrophy and stimulate muscle atrophy via the activation of the autophagy and ubiquitin-proteasome systems. Many reports including our own Indacaterol Maleate indicate that Dex increases the mRNAs of these autophagy-and ubiquitin-proteasome-related proteins and that BCAA suppresses these increases. In contrast to these previous studies, BCAA did not affect Bnip3, atrogin-1 or MuRF1 mRNA levels in the present study. GSK343 Collectively, BCAA appeared to lose its bioactivity in SDR muscles. GH-treatment restored the actions of BCAA on the SDR muscles. After the GH administration, Dex decreased the CSA of SDR muscle fibers and BCAA suppressed the Dex-induced decrease in CSA in accordance with the recovery of intracellular signal transmission, which included the phosphorylations of p70S6K, suggesting the activation of mTOR.