Single-fiber and whole muscle analyses of MHC isoform plasticity: interaction between T-3 and unloading
Single-fiber and whole muscle analyses of MHC isoform plasticity: interaction between T-3 and unloading
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DOI：
10.1152/ajpcell.1997.273.3.c944
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发表时间：
1997-09-01
影响因子：
5.5
通讯作者：
Baldwin, KM
中科院分区：
文献类型：
--
作者：
Caiozzo, VJ;Baker, MJ;Baldwin, KM
以前的数据表明，甲状腺功能亢进症（T-3）和后肢悬吊（HS）的单独干预作用于比目鱼肌中的一些但不是所有的慢I型纤维。这可能是由于存在“难治性”纤维，这些纤维对这些干预措施中的任何一种都没有反应。或者，T-3和HS可能作用于比目鱼肌中不同群体的慢I型纤维。将成年雌性Sprague-Dawley大鼠分配至ii对照组、2）T-3组、3）HS组或4）T-3+HS组。每组分配9只动物。比目鱼肌的单纤维电泳分析（n = 40每块肌肉）表明，HS降低了慢I型纤维的百分比从类似于80%（对照）到类似于40%（HS）的纤维人口。虽然甲状腺功能亢进症影响的Blow I型纤维的百分比比I-IS更大，但一小部分人（类似于10%的慢I型纤维）不受T-3的影响。相比之下，联合干预将所有慢速I型纤维转化为表达快速肌球蛋白重链（MHC）亚型的各种组合的纤维。这些发现表明比目鱼肌不包含所谓的不应纤维。他们进一步表明，比目鱼肌包含不同群体的I型慢纤维，它们对生理条件改变的敏感性不同。
Previous data suggest that separate interventions of hyperthyroidism (T-3) and hindlimb suspension (HS) act on some but not all slow type I fibers in the soleus muscle. This may be due to the presence of ''refractory'' fibers that are unresponsive to either of these interventions. Alternatively, T-3 and HS might act on different populations of slow type I fibers in the soleus muscle. Adult female Sprague-Dawley rats were assigned to ii control, 2) T-3, 3) HS, or 4) T-3+HS. Nine animals were assigned to each group. Single-fiber electrophoretic analyses (n = 40 per muscle) of the soleus muscle demonstrated that the HS reduced the percentage of slow type I fibers from similar to 80% (control) to similar to 40% (HS) of the fiber population. Although hyperthyroidism affected a greater percentage of Blow type I fibers than I-IS, a small population (similar to 10% of the slow type I fibers) were unaffected by T-3. The combined intervention, in contrast, transformed all slow type I fibers into fibers expressing various combinations of fast myosin heavy chain (MHC) isoforms. These findings demonstrate that the soleus muscle does not contain so-called refractory fibers. They further suggest that the soleus muscle contains different populations of slow type I fibers that vary in their sensitivity to altered physiological conditions.