Alteration in albumin level during modified muscular activity.

We have previously reported that albumin protein is increased in the atrophied muscle induced by hindlimb immobilization. The purpose of this study was to evaluate the effects of several disuse models on albumin protein and mRNA levels in mice skeletal muscle and to investigate whether the elevated amount of albumin returns to control level by muscular activity increased by hindlimb remobilization. Western blot analysis revealed that hindlimb immobilization, denervation, and tenotomy, except for hindlimb unloading, significantly increased albumin levels in soleus muscles by 2.1-, 1.9- and 2.0-fold, respectively (P < 0.001). Immunohistochemical analysis showed that albumin protein accumulates in the widened extracellular space. Reverse transcription-polymerase chain reaction (RT-PCR) assay revealed albumin gene expression to be downregulated in all disuse models relative to control level. During hindlimb remobilization, the amounts of albumin protein appeared to remain higher level after 3 and 7 days and had returned to control level after 14 days and muscle mass, the amounts of myosin heavy chain, and actin proteins seemed to restore control levels after 21 days. These results indicate that the amount of interstitial albumin protein may be modulated by muscular activity.