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Effects of antigravity muscular activity during the lactation period on the development of rat hindlimb muscles

哺乳期抗重力肌活动对大鼠后肢肌肉发育的影响

基本信息

批准号：
12480010
负责人：
OHIRA Yoshinobu
金额：
$ 10.43万
依托单位：
Osaka University (2001-2002)National Institute of Fitness and Sports in Kanoya (2000)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Effects of hindlimb suspension or loading at 2-g during the first 3-month of life on the development of hindlimb muscles were studied in rats. The growth of ankle plantar-flexor soleus was inhibited by hindlimb suspension of new-born rats. Although the growth-related increases of muscle fiber number and longitudinal growth were not affected, the increase of fiber cross-sectional area, fiber-type transformation toward slow-twitch type, and the change of fiber innervation from multiple to single were inhibited by suspension. These phenomena were associated with lower levels of myonuclear number, DNA content within a nucleus, and/or satellite cell number. However, the effects of suspension on the growth of other plantar-flexors, gastrocnemius and plantaris (fast twitch muscle), were minor, even their growth was inhibited in some degree. The growth of dorsi-flexors, extensor digitorum longus and tibialis anterior (TA, fast twitch muscle), was not influenced by suspension at all. It was suggested that the growth-associated shift of muscle fiber type in soleus is not programmed genetically but is closely related to the tonic activity of the muscle itself. The significant effect of afferent input, which is directly influenced by muscle activity, on the differentiation of fiber type was also suggested.The expressions of gene, such as cathepsin L, heat shock protein 27, in soleus muscle, which are inhibited during the normal growth, were even increased in response to chronic unloading. The expression of heat shock protein 70 was, on the contrary, inhibited by unloading. The expressions of ubiquitin-conjugating enzyme E2, mitochondrial ATP synthase B subunit precursor were increased following growth and further promoted by unloading. Although cathepsin H, cathepsin K, insulin-like growth factor (IGF1) were not influenced, those of myosin light chain 1 and 3, heat shock 20kDa protein, create kinase, αB-crystallin were inhibited following unload.ing.

本文研究了出生后3个月内后肢悬吊或负重2g对大鼠后肢肌肉发育的影响。新生大鼠后肢悬吊抑制踝跖屈肌比目鱼肌的生长。虽然与生长相关的肌纤维数量和纵向生长的增加不受影响，但纤维横截面积的增加，纤维类型向慢收缩型的转变，以及纤维神经支配从多个到单个的变化受到抑制。这些现象与较低水平的肌细胞数量，细胞核内的DNA含量，和/或卫星细胞数量。然而，悬吊对其他跖屈肌（腓肠肌和跖肌）的生长影响较小，甚至有一定程度的抑制作用。背屈肌、趾长伸肌和胫骨前肌（TA，快缩肌）的生长完全不受悬吊的影响。结果表明，比目鱼肌肌纤维类型的变化与生长有关，但与肌肉本身的紧张性活动密切相关。比目鱼肌中组织蛋白酶L、热休克蛋白27等基因的表达在正常生长时受到抑制，而在慢性去负荷时甚至增加。热休克蛋白70的表达，相反，抑制卸载。泛素结合酶E2、线粒体ATP合成酶B亚基前体的表达随细胞生长而增加，并随细胞卸载而进一步增加。组织蛋白酶H、组织蛋白酶K、胰岛素样生长因子1（IGF 1）在去负荷后不受影响，而肌球蛋白轻链1和3、热休克蛋白20 kDa、肌酸激酶、α B-晶状体蛋白等在去负荷后受到抑制。