Takemura Ai, Roy Roland R, Edgerton V Reggie, Ishihara Akihiko
Aerosp Med Hum Perform. 2016 May;87(5):443-8. doi: 10.3357/AMHP.4436.2016.
Chronic unloading and restricted activity are distinctly different processes, i.e., unloading completely removes the load on postural muscles, whereas restricted activity allows for loading of postural muscles. There are limited data available on the effects of restricted activity on skeletal muscles. Thus the effects of restricted activity on the properties of the slow soleus and fast plantaris muscles in rats were examined.
Eight-week-old rats were housed for 21 d in normal-sized (control group) or in small-sized (restricted group) cages.
Decreased mRNA levels of peroxisome proliferator-activated receptor γ coactivator-1α (81 and 85% of control values) and reduced succinate dehydrogenase activity (85 and 88% of control values) were observed in the soleus and the plantaris muscles of the restricted group, respectively. Increased mRNA levels of forkhead box-containing protein O1 (128% of control values), decreased muscle weight (74% of control values), and reduced cross-sectional areas of type IIA (89% of control values) and type IIB (80% of control values) fibers were observed in the plantaris muscle of the restricted group.
Restricted activity decreased the mRNA levels of peroxisome proliferator-activated receptor γ coactivator-1α and increased the mRNA levels of forkhead box-containing protein O1, which are associated with reduced oxidative capacity and atrophy, respectively, in the muscles. The plantaris muscle was more affected by restricted activity than the soleus muscle, most likely reflecting a greater relative change in the normal activity pattern in the fast than slow plantarflexor muscle. Takemura A, Roy RR, Edgerton VR, Ishihara A. Biochemical adaptations in a slow and a fast plantarflexor muscle of rats housed in small cages.
慢性卸载和活动受限是截然不同的过程，即卸载完全消除了对姿势肌的负荷，而活动受限则允许姿势肌承受负荷。关于活动受限对骨骼肌影响的数据有限。因此，研究了活动受限对大鼠慢比目鱼肌和快跖肌特性的影响。
将8周龄大鼠饲养在正常大小（对照组）或小尺寸（活动受限组）的笼子中21天。
在活动受限组的比目鱼肌和跖肌中，分别观察到过氧化物酶体增殖物激活受体γ辅激活因子-1α的mRNA水平降低（分别为对照值的81%和85%）以及琥珀酸脱氢酶活性降低（分别为对照值的85%和88%）。在活动受限组的跖肌中，观察到含叉头框蛋白O1的mRNA水平升高（为对照值的128%）、肌肉重量降低（为对照值的74%）以及IIA型（为对照值的89%）和IIB型（为对照值的80%）纤维的横截面积减小。
活动受限降低了过氧化物酶体增殖物激活受体γ辅激活因子-1α的mRNA水平，并增加了含叉头框蛋白O1的mRNA水平，这分别与肌肉中氧化能力降低和萎缩有关。跖肌比目鱼肌受活动受限的影响更大，这很可能反映了快肌比慢肌在正常活动模式下相对变化更大。 武村A、罗伊RR、埃杰顿VR、石原A。饲养在小笼子中的大鼠慢、快跖屈肌的生化适应性变化。
