Specific protein alteration in the soleus following immobilization-atrophy.

To investigate the effect of immobilization in a shortened position on protein alteration in the mouse soleus, total protein from immobilized and control muscle were analyzed by SDS-PAGE and two-dimensional polyacrylamide gel electrophoresis. Five-week-old male ddY mice (n=22) were used throughout this study. A 67.3 kDa protein was significantly increased by 1.7-fold in the immobilized muscles in SDS-PAGE compared to control muscle (P<0.001). This protein had the same mobility as serum albumin. The isoelectric point of the 67.3 kDa protein was pH 6.3, similar to serum albumin (range from pH 6.0 to 6.3). Specific antibody to the 67.3 kDa protein reacted with serum albumin by Western blot analysis. This protein was localized in the interstitial space in the control muscle and accumulated in pathologic areas in the immobilized muscle. It was presumed that this protein was a serum albumin-like protein.