Decrease in human quadriceps muscle protein turnover consequent upon leg immobilization.

摘要: 1. Quadriceps muscle protein turnover was assessed in the post-absorptive state six men immediately after end of unilateral leg immobilization (37 ± 4 days) a plaster cast tibial fracture. A primed-constant intravenous infusion l-[1- 13 C]leucine administered over 7 h. needle biopsies, taken bilaterally at infusion, were analysed for leucine enrichment with C. 2. synthetic rate, calculated from fractional incorporation [ into compared average blood α-ketoisocaproate, 0.046 ±0.012%/h uninjured leg, but only 0.034 ±0.007%/h quadriceps previously fractured ( P > 0.05, means sd). 3. Muscle RNA activity (i.e. rate per RNA) fell 0.27 ±0.08 μg synthesized h −1 control to 0.14 ±0.03 immobilized 0.02). 4. Immobilization associated significant atrophy type I fibres (mean diameter 69.5 ±21 μm immobilized, 81.1 ±18 control, 0.05), no change occurred II fibre diameter. Mean volume values and percentage each type, smaller injured by 10.6%; this value near difference thigh (calculated circumference skin-fold thickness) which less 8.3%. 5. From estimated mean daily (1.65 ±0.44%/day legs 1.22±0.28%/day legs) volume, breakdown rates as 1.65%/ day 1.53%/day respectively, suggesting that not enhanced may have fallen. 6. The results suggest decrease during limb man, decrement mass being due mainly substantial (25%) depression synthesis.