Myonuclear number and myosin heavy chain expression in rat soleus single muscle fibers after spaceflight
Myonuclear number and myosin heavy chain expression in rat soleus single muscle fibers after spaceflight
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DOI：
10.1152/jappl.1996.81.1.145
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发表时间：
1996-07-01
影响因子：
3.3
通讯作者：
Edgerton, VR
中科院分区：
文献类型：
--
作者：
Allen, DL;Yasui, W;Edgerton, VR
本文研究了14天的太空飞行对大鼠比目鱼肌肌纤维节段肌纤维数目、肌纤维大小和肌球蛋白重链（MHC）表达的影响。通过共聚焦显微镜和凝胶电泳，将执行太空实验室生命科学-2号14天使命的大鼠的比目鱼肌纤维与年龄匹配的地面对照大鼠的比目鱼肌纤维进行了比较。太空飞行导致表达I型MHC的纤维数量显著减少，表达IIx或IIa型MHC的纤维数量增加。太空飞行还导致共表达一种以上MHC的纤维的百分比增加，以及某些纤维中新生儿MHC亚型的再表达。纤维横截面积显着减少，在纯I型MHC表达的纤维和共表达I+II型MHC的纤维，但不表达一个或多个II型MHC的纤维在飞行大鼠。每毫米的肌细胞核的数量显着减少，在I型MHC表达纤维的飞行大鼠，但没有显着差异，在I+II型和II型MHC共表达纤维。表达新生儿MHC的纤维在大小上与对照纤维相似，但每毫米肌核数显著少于不表达新生儿MHC的飞行纤维。在I型MHC表达的纤维中，纤维横截面积的减少大于肌纤维数量的减少;因此，每个肌核的平均细胞质体积在飞行中显著低于对照纤维。14天的航天飞行后，表达I型MHC的肌纤维数量和纤维大小的减少支持了这样一种假设，即肌细胞核数量的变化可能是与肌肉组织慢性卸载相关的纤维大小减少的一个促成因素。
The effects of 14 days of spaceflight on myonuclear number, fiber size, and myosin heavy chain (MHC) expression in isolated rat soleus muscle fiber segments were studied. Single soleus muscle fibers from rats flown on the Spacelab Life Sciences-2 14-day mission were compared with those from age-matched ground-based control rats by using confocal microscopy and gel electrophoresis. Spaceflight resulted in a significant reduction in the number of fibers expressing type I MHC and an increase in the number of fibers expressing type IIx or IIa MHC. Spaceflight also resulted in an increase in the percentage of fibers coexpressing more than one MHC and in the reexpression of the neonatal isoform of MHC in some fibers. Fiber cross-sectional area was significantly reduced in pure type I MHC-expressing fibers and in fibers coexpressing type I+II MHC but not in fibers expressing one or more type II MHC in the flight rats. The number of myonuclei per millimeter was significantly reduced in type I MHC-expressing fibers from the flight rats but was not significantly different in type I+II and type II MHC-coexpressing fibers. Fibers expressing neonatal MHC were similar in size to control fibers but had significantly fewer myonuclei per millimeter than flight fibers not expressing neonatal MHC. In type I MHC-expressing fibers, the reduction in fiber cross-sectional area was greater than the reduction in myonuclear number; thus the average cytoplasmic volume per myonucleus was significantly lower in flight than in control fibers. The reduction in both myonuclear number and fiber size of fibers expressing type I MHC after 14 days of spaceflight supports the hypothesis that changes in the number of myonuclei may be a contributing factor to the reduction in fiber size associated with chronic unloading of the musculature.