Ageing and dexamethasone associated sarcopenia: peculiarities of regeneration.

The purpose of this study was to assess the development of ageing- and glucocorticoid-related sarcopenia on the level of myofibrillar apparatus, paying attention to the synthesis (SR) and degradation rate (DR) of contractile proteins, muscle strength, and daily motor activity. We also wanted to test the effect of ageing and dexamethasone (Dex) excess on the regeneration peculiarities of skeletal muscle autografts. Four and 30-month-old male rats of the Wistar strain were used. Ageing associated sarcopenia was calculated from gastrocnemius muscle relative mass decrease (from 5.6 +/- 0.08 to 3.35 +/- 0.04; p < 0.001). The SR of MyHC in old rats was approximately 30% and actin approximately 23% lower than in young rats. Dex treatment decreased SR of two main contractile proteins significantly in both age groups (p < 0.001) and increased DR during ageing from 2.11 +/- 0.15 to 4.09 +/- 0.29%/day (p < 0.001). Hindlimb grip strength in young rats was 5.90 +/- 0.35 N/100 g bw and 2.64 +/- 0.2 N/100 g bw (p < 0.001) in old rats. Autografts of old rats have a higher content of adipose tissue 14.9 +/- 1.1% in comparison with young rats 6.8 +/- 0.51% (p < 0.001) and less muscle tissue 39.8 +/- 2.6% and 48.3 +/- 2.8%, respectively (p < 0.05). Both, ageing and dex-caused sarcopenic muscles have diminished capacity for regeneration.