Symons T B, Sheffield-Moore M, Chinkes D L, Ferrando A A, Paddon-Jones D
The Univ. of Texas Medical Branch, 301 Univ. Blvd., Galveston, TX 77555-1144, USA.
J Appl Physiol (1985). 2009 Jul;107(1):34-8. doi: 10.1152/japplphysiol.91137.2008. Epub 2009 Apr 23.
We sought to determine the effects of longitudinal loading (artificial gravity) on skeletal muscle protein kinetics in 15 healthy young males after 21 days of 6 degrees head-down tilt bed rest [experimental treatment (Exp) group: n = 8, 31 +/- 1 yr; control (Con) group; n = 7, 28 +/- 1 yr, means +/- SE]. On days 1 and 21 of bed rest, postabsorptive venous blood samples and muscle biopsies (vastus lateralis and soleus) were obtained during a 1-h pulse bolus infusion protocol (0 min, l-[ring-(13)C(6)]phenylalanine, 35 mumol/kg; 30 min, l-[ring-(15)N]phenylalanine, 35 mumol/kg). Outcome measures included mixed muscle fractional synthesis (FSR) and breakdown rates (FBR). The Exp group experienced 1 h of longitudinal loading (2.5G at the feet) via a short-radius centrifuge during each day of bed rest. Mixed muscle FSR in the Con group was reduced by 48.5% (day 1, 0.081 +/- 0.000%/h vs. day 21, 0.042 +/- 0.000%/h; P = 0.001) in vastus lateralis after 21 days of bed rest, whereas the Exp group maintained their rate of protein synthesis. A similar but nonsignificant change in FSR was noted for the soleus muscle (Exp, -7%; Con, -22%). No changes in muscle protein breakdown were observed. In conclusion, 1 h of daily exposure to artificial gravity maintained the rate of protein synthesis of the vastus lateralis and may represent an effective adjunct countermeasure to combat the loss of muscle mass and functional during extended spaceflight.
我们试图确定在15名健康年轻男性经历21天6度头低位卧床休息后，纵向负荷（人工重力）对骨骼肌蛋白质动力学的影响[实验治疗（Exp）组：n = 8，31±1岁；对照组（Con）：n = 7，28±1岁，均值±标准误]。在卧床休息的第1天和第21天，在1小时脉冲推注方案（0分钟，l-[环-(13)C(6)]苯丙氨酸，35 μmol/kg；30分钟，l-[环-(15)N]苯丙氨酸，35 μmol/kg）期间采集空腹静脉血样和肌肉活检样本（股外侧肌和比目鱼肌）。观察指标包括混合肌肉的合成率（FSR）和分解率（FBR）。Exp组在卧床休息的每一天通过短半径离心机经历1小时的纵向负荷（足部2.5G）。卧床休息21天后，Con组股外侧肌的混合肌肉FSR降低了48.5%（第1天，0.081±0.000%/小时 vs. 第21天，0.042±0.000%/小时；P = 0.001），而Exp组维持了其蛋白质合成速率。比目鱼肌的FSR有类似但不显著的变化（Exp组，-7%；Con组，-22%）。未观察到肌肉蛋白质分解的变化。总之，每天1小时暴露于人工重力可维持股外侧肌的蛋白质合成速率，可能是对抗长期太空飞行期间肌肉质量和功能丧失的一种有效辅助对策。
