5.1. General responses to immobilization, glucocorticoids and exercise (I, II, III)

The body mass of the rats decreased during the first day of immobilization, but normal weight gain was achieved by the 7^th day of immobilization. Dexamethasone treatment decreased the body mass of the rats already during the first three days. After 10 days, the body mass of all dexamethasone-treated animals was much lower compared to rats without steroid treatment. Both endurance and uphill running exercise increased body mass during 10 days, although exercise combined with dexamethasone treatment even enhanced the decrease in body mass during the first three days. The muscle mass of all muscles studied decreased during both immobilization and dexamethasone treatment. During immobilization, muscle mass of SOL and GM were decreased the most, and shortened position further enhanced the decrease. Exercise only slightly increased the mass of SOL, and it had no effect on the weight of other muscles. However, endurance type of exercise prevented the dexamethasone-induced muscle weight loss in EDL and SOL.

Total RNA content was decreased after immobilization first in GM, and then after three days also in SOL. No change in the RNA content was observed in EDL and TA during immobilization. During dexamethasone treatment, a decrease in the RNA content was observed first in SOL and TA, and after 10 days also in EDL. No changes in soluble protein concentration were observed during immobilization and dexamethasone treatment, except for a slight increase in lengthened SOL after 3 days and shortened TA after 7 days of immobilization. After 7 days of immobilization, soluble protein content (mg/muscle) was decreased in shortened SOL.