Figure 3. Effect of hindlimb unloading (HU) and reloading on muscle protein synthesis and total RNA in adult and old rats. (A) Using the SUnSET method, protein synthesis was measured in the soleus and tibialis anterior (TA) muscles of adult (9 mo, open squares) and old (29 mo, filled squares) rats after 14 days of HU and after 3, 7, and 14 days of reloading. Total protein, determined by stain-free imaging of the PVDF membrane, was used to normalize protein expression. Puromycin values are expressed as a percentage of each age-matched control group (n=6-7/group). Total RNA (μg/mg muscle) was measured in the soleus (B) and TA (C) muscles of adult (open squares) and old (filled squares) rats after 14 days of HU and after 1, 3, 7, and 14 days of reloading (n=6/group). Values are mean ± SEM, *p<0.05 vs adult control, #p<0.05 vs old control, φp<0.05 vs adult at same time point.