Yoshida N, Ikata T, Sairyo K, Matsuura T, Sasa T, Koga K, Fukunaga M
Department of Orthopedic Surgery, School of Medicine, University of Tokushima.
J Physiol Anthropol Appl Human Sci. 2001 Jul;20(4):247-52. doi: 10.2114/jpa.20.247.
The purpose of this study was to evaluate disuse atrophy of skeletal muscle using a hind-limb suspension model, with special reference to energy metabolism. Twenty-four Sprague-Dawley rats were divided into four groups: control group (C), hind-limb suspended for 3 days (HS-3), for 7 days (HS-7) and for 14 days (HS-14). The gastrocnemius-plantaris-soleus (GPS) muscles in each group were subjected to the following measurements. After a 2-min rest, contraction of the GPS muscles was induced by electrical stimulation of the sciatic nerve at 0.25 Hz for 10 min, then the frequency was increased to 0.5 and 1.0 Hz every 10 min. During the stimulation, twitch forces were recorded by a strain gauge, and 31P-MRS was performed simultaneously. Maximum tension was measured at the muscle contraction induced at 0.25 Hz; the wet weight of the whole and each muscle in the GPS muscles was also measured. From the 31P-MR spectra during muscle contraction, the oxidative capacity was calculated and compared among the groups. The weights of the whole GPS muscles in C, HS-3, HS-7 and HS-14, were 2.66 +/- 0.09, 2.39 +/- 0.21, 2.34 +/- 0.21 and 2.18 +/- 0.14 (g) respectively. Thus, the muscle mass significantly decreased with time (p < 0.05). Among the GPS muscles, the decrease in weight of the soleus muscle was especially remarkable; in the HS-14 group its weight decreased to 60% of that in the C group. We evaluated maximum tension and oxidative capacity as the muscle function. The maximum tensions in C, HS-3, HS-7 and HS-14 were 519 +/- 43, 446 +/- 66, 450 +/- 23 and 465 +/- 29 (g), respectively. This was significantly greater in the C group than in any other groups, however there were no significant differences among the three HS groups. The oxidative capacity during muscle contraction in the C group was higher than in any HS group and it did not further decrease even if the suspension of the limbs was prolonged beyond 3 days. The present study showed that in disuse atrophy, muscle mass and muscle function did not change simultaneously. Thus, it is necessary to develop countermeasures to prevent muscle atrophy and muscle function deterioration independently.
本研究的目的是使用后肢悬吊模型评估骨骼肌的废用性萎缩，特别关注能量代谢。将24只Sprague-Dawley大鼠分为四组：对照组（C）、后肢悬吊3天（HS-3）、悬吊7天（HS-7）和悬吊14天（HS-14）。对每组的腓肠肌-比目鱼肌-跖肌（GPS）进行以下测量。休息2分钟后，通过以0.25Hz的频率电刺激坐骨神经10分钟来诱导GPS肌肉收缩，然后每10分钟将频率增加到0.5Hz和1.0Hz。在刺激过程中，用应变片记录抽搐力，并同时进行31P-MRS。在0.25Hz诱导的肌肉收缩时测量最大张力；还测量了GPS肌肉整体及每块肌肉的湿重。根据肌肉收缩期间的31P-MR光谱计算氧化能力并在各组之间进行比较。C组、HS-3组、HS-7组和HS-14组的整个GPS肌肉重量分别为2.66±0.09、2.39±0.21、2.34±0.21和2.18±0.14（g）。因此，肌肉质量随时间显著下降（p<0.05）。在GPS肌肉中，比目鱼肌重量的下降尤为明显；在HS-14组中，其重量降至C组的60%。我们将最大张力和氧化能力评估为肌肉功能。C组、HS-3组、HS-7组和HS-14组的最大张力分别为519±43、446±66、450±23和465±29（g）。C组的最大张力显著高于其他任何组，然而三个HS组之间没有显著差异。C组肌肉收缩期间的氧化能力高于任何HS组，即使肢体悬吊时间延长超过3天，其氧化能力也不会进一步降低。本研究表明，在废用性萎缩中，肌肉质量和肌肉功能并非同时发生变化。因此，有必要分别制定预防肌肉萎缩和肌肉功能恶化的对策。
