Ingalls C P, Wenke J C, Armstrong R B
Department of Health & Kinesiology, Texas A&M University, College Station, USA.
Aviat Space Environ Med. 2001 May;72(5):471-6.
Exposure to reduced gravitational forces during spaceflight is associated with significant reductions in skeletal muscle mass and strength. The purpose of this study was to test the hypothesis that increases in resting cytosolic free calcium concentration ([Ca2+]i) would precede reductions in protein content and maximal isometric tetanic force (Po) in mouse soleus muscle after initiation of hindlimb suspension.
Female ICR mice (n = 42) were hindlimb suspended for 1, 2, 3, 5, or 7 d; weight-matched mice were used as controls. Following the hindlimb suspension, the left soleus muscle was used to determine Po in vitro and the right soleus muscle was used to determine protein content and [Ca2+]i via confocal laser scanning microscopy.
Compared with controls, [Ca2+]i was elevated by 38% at 2 d, and 117% at 7 d. Compared with controls, soleus muscle total and myofibrillar protein contents were reduced 27-29% and 30-34%, respectively, at 5-7 d after initiation of hindlimb suspension. Compared with controls, soleus muscle Po was decreased by 24% at 3 d, and 38% at 7 d.
It appears that resting cytosolic Ca2+ homeostasis is disturbed soon after the initiation of hindlimb suspension, and these elevations in [Ca2+]i may play a role in initiating soleus muscle atrophy.
太空飞行期间暴露于低重力环境会导致骨骼肌质量和力量显著下降。本研究的目的是检验以下假设：后肢悬吊开始后，小鼠比目鱼肌静息胞质游离钙浓度（[Ca2+]i）升高会先于蛋白质含量和最大等长强直收缩力（Po）降低。
将42只雌性ICR小鼠后肢悬吊1、2、3、5或7天；体重匹配的小鼠作为对照。后肢悬吊后，取左侧比目鱼肌用于体外测定Po，右侧比目鱼肌用于通过共聚焦激光扫描显微镜测定蛋白质含量和[Ca2+]i。
与对照组相比，[Ca2+]i在2天时升高38%，在7天时升高117%。与对照组相比，后肢悬吊开始后5至7天，比目鱼肌总蛋白和肌原纤维蛋白含量分别降低27 - 29%和30 - 34%。与对照组相比，比目鱼肌Po在3天时降低24%，在7天时降低38%。
后肢悬吊开始后不久，静息胞质Ca2+稳态似乎就受到干扰，[Ca2+]i的这些升高可能在引发比目鱼肌萎缩中起作用。
