Identification of the optimal dose and calpain system regulation of tetramethylpyrazine on the prevention of skeletal muscle atrophy in hindlimb unloading rats

Previous studies in our lab have shown that tetramethylpyrazine (TMP) could effectively attenuate disuse induced muscle atrophy. In order to screening out the optimal dose of tetramethylpyrazine (TMP) for protection against disuse induced muscle atrophy in hindlimb unloading (HLU) rats, in this study, we compared effects of 4 TMP doses on muscle wet weight (MWW), the ratios of muscle wet weight/body weight (MWW/BW) and muscle wet weight/dry weight (MWW/DW), fiber type composition, as well as cross-sectional area (CSA) in soleus (SOL) muscle. Consequently, we quantified optimal dose effects on both functional properties and protein expression (calpain-1, calpain-2, calpastatin and MuRF1) in SOL and extensor digitorum longus (EDL) muscles. Data indicated that the protective potential of TMP was dose-dependent: 60mg/kg TMP was most effective in terms of atrophy prevention. This dose reduced SOL MWW, MWW/BW and CSA muscle loss by 60, 60 and 54% (P