Staron R S, Kraemer W J, Hikida R S, Reed D W, Murray J D, Campos G E, Gordon S E
Department of Biological Sciences, College of Osteopathic Medicine, Ohio University, Athens 45701, USA.
Histochem Cell Biol. 1998 Jul;110(1):73-80. doi: 10.1007/s004180050267.
The effects of two different duration space-flights on the extent of atrophy, fiber type composition, and myosin heavy chain (MHC) content of rat soleus muscles were compared. Adult male Fisher rats (n=12) were aboard flight STS-57 and exposed to 10 days of microgravity and adult ovariectomized female Spraque-Dawley rats (n=12) were aboard flight STS-62 for 14 days. Soleus muscles were bilaterally removed from the flight and control animals and frozen for subsequent analyses. Muscle wet weights, fiber types (I, IC, IIC, and IIA), cross-sectional area, and MHC content were determined. Although a significant difference was found between the soleus wet weights of the two ground-based control groups, they were similar with regard to MHC content (ca 90% MHCI and ca 10% MHCIIa) and fiber type composition. Unloading of the muscles caused slow-to-fast transformations which included a decrease in the percentage of type I fibers and MHCI, an increase in fibers classified as type IC, and the expression of two fast myosin heavy chains not found in the control rat soleus muscles (MHCIId and MHCIIb). Although the amount of atrophy (ca 26%) and the extent of slow-to-fast transformation (decrease in the percentage of MHCI from 90% to 82.5%) in the soleus muscles were similar between the two spaceflights, the percentages of the fast MHCs differed. After 14 days of spaceflight, the percentage of MHCIIa was significantly lower and the percentages of MHCIId and MHCIIb were significantly higher than the corresponding MHC content of the soleus muscles from the 10-day animals. Indeed, MHCIId became the predominant fast MHC after 14 days in space. These data suggest fast-to-faster transformations continued during the longer spaceflight.
比较了两种不同时长的太空飞行对大鼠比目鱼肌萎缩程度、纤维类型组成和肌球蛋白重链（MHC）含量的影响。成年雄性Fisher大鼠（n = 12）搭乘STS - 57航班，暴露于10天的微重力环境中，成年去卵巢雌性Sprague - Dawley大鼠（n = 12）搭乘STS - 62航班，暴露于14天的微重力环境中。从飞行组和对照组动物双侧取下比目鱼肌并冷冻，以备后续分析。测定肌肉湿重、纤维类型（I、IC、IIC和IIA）、横截面积和MHC含量。虽然两个地面对照组的比目鱼肌湿重存在显著差异，但它们在MHC含量（约90% MHCI和约10% MHCIIa）和纤维类型组成方面相似。肌肉卸载导致了从慢肌纤维到快肌纤维的转变，包括I型纤维和MHCI百分比的降低、IC型纤维百分比的增加，以及在对照大鼠比目鱼肌中未发现的两种快肌球蛋白重链（MHCIId和MHCIIb）的表达。虽然两次太空飞行中比目鱼肌的萎缩量（约26%）和从慢肌纤维到快肌纤维的转变程度（MHCI百分比从90%降至82.5%）相似，但快肌MHC的百分比有所不同。太空飞行14天后，MHCIIa的百分比显著低于10天太空飞行动物比目鱼肌的相应MHC含量，而MHCIId和MHCIIb的百分比则显著高于该含量。实际上，在太空飞行14天后，MHCIId成为主要的快肌MHC。这些数据表明，在更长时间的太空飞行中，快肌纤维向更快肌纤维的转变仍在继续。
