Carraro F, Stuart C A, Hartl W H, Rosenblatt J, Wolfe R R
Department of Anesthesiology, Shriners Burns Institute, Galveston, Texas.
Am J Physiol. 1990 Oct;259(4 Pt 1):E470-6. doi: 10.1152/ajpendo.1990.259.4.E470.
Previous studies using indirect means to assess the response of protein metabolism to exercise have led to conflicting conclusions. Therefore, in this study we have measured the rate of muscle protein synthesis in normal volunteers at rest, at the end of 4 h of aerobic exercise (40% maximal O2 consumption), and after 4 h of recovery by determining directly the rate of incorporation of 1,2-[13C]leucine into muscle. The rate of muscle protein breakdown was assessed by 3-methylhistidine (3-MH) excretion, and total urinary nitrogen excretion was also measured. There was an insignificant increase in 3-MH excretion in exercise of 37% and a significant increase (P less than 0.05) of 85% during 4 h of recovery from exercise (0.079 +/- 0.008 vs. 0.147 +/- 0.0338 mumol.kg-1.min-1 for rest and recovery from exercise, respectively). Nonetheless, there was no effect of exercise on total nitrogen excretion. Muscle fractional synthetic rate was not different in the exercise vs. the control group at the end of exercise (0.0417 +/- 0.004 vs. 0.0477 +/- 0.010%/h for exercise vs. control), but there was a significant increase in fractional synthetic rate in the exercise group during the recovery period (0.0821 +/- 0.006 vs. 0.0654 +/- 0.012%/h for exercise vs. control, P less than 0.05). Thus we conclude that although aerobic exercise may stimulate muscle protein breakdown, this does not result in a significant depletion of muscle mass because muscle protein synthesis is stimulated in recovery.
以往使用间接方法评估蛋白质代谢对运动反应的研究得出了相互矛盾的结论。因此，在本研究中，我们通过直接测定1,2-[13C]亮氨酸掺入肌肉的速率，来测量正常志愿者在静息状态、有氧运动4小时（最大耗氧量的40%）结束时以及恢复4小时后的肌肉蛋白质合成速率。通过3-甲基组氨酸（3-MH）排泄评估肌肉蛋白质分解速率，并测量总尿氮排泄量。运动时3-MH排泄量有37%的不显著增加，运动恢复4小时期间显著增加（P<0.05），增加了85%（静息和运动恢复时分别为0.079±0.008与0.147±0.0338μmol·kg-1·min-1）。尽管如此，运动对总氮排泄没有影响。运动结束时，运动组与对照组的肌肉分数合成率无差异（运动组与对照组分别为0.0417±0.004与0.0477±0.010%/小时），但运动组在恢复期间分数合成率显著增加（运动组与对照组分别为0.0821±0.006与0.0654±0.012%/小时，P<0.05）。因此，我们得出结论，尽管有氧运动可能刺激肌肉蛋白质分解，但这并不会导致肌肉质量显著减少，因为恢复过程中肌肉蛋白质合成受到刺激。
