Yoshioka T, Shirota T, Tazoe T, Yamashita-Goto K
Department of Physiology, St Marianna University School of Medicine, Kawasaki, Japan.
Acta Astronaut. 1996 Feb;38(3):209-12. doi: 10.1016/0094-5765(96)00010-0.
The function of the sarcoplasmic reticulum (SR) was examined in the slow soleus and fast extensor digitorum longus (EDL) muscles of rats submitted to 14 days of weightlessness produced by hindlimb suspension (HS). Ca2+ uptake, Ca2+ release and passive Ca2+ leakage through the SR membrane were investigated using a method of caffeine-induced contracture on the single mechanically skinned fibers. In the SR of suspended soleus muscles, the rate of Ca2+ uptake was higher than in the control muscles. However, there was no difference between the suspended and control muscles in the rate of Ca2+ uptake of the SR in EDL after HS. In soleus muscles, Ca2+ movements of the SR from the suspended muscle acquired the properties that were similar to those of the control fast muscle. The study of Ca2+ leakage showed that the velocity and amount of passive Ca2+ leakage from SR in soleus and EDL were apparently increased after HS. The results suggested that the functional properties of the SR membrane in slow and fast muscles were changed after HS.
通过后肢悬吊（HS）使大鼠产生14天失重状态，在此条件下检测了比目鱼肌（慢肌）和趾长伸肌（EDL，快肌）中肌浆网（SR）的功能。采用咖啡因诱导单根机械去表皮肌纤维挛缩的方法，研究了SR膜的Ca2+摄取、Ca2+释放和被动Ca2+泄漏情况。在悬吊比目鱼肌的SR中，Ca2+摄取速率高于对照肌肉。然而，HS后EDL中SR的Ca2+摄取速率在悬吊肌肉和对照肌肉之间没有差异。在比目鱼肌中，悬吊肌肉的SR的Ca2+运动获得了与对照快肌相似的特性。Ca2+泄漏研究表明，HS后比目鱼肌和EDL中SR被动Ca2+泄漏的速度和量明显增加。结果表明，HS后慢肌和快肌中SR膜的功能特性发生了改变。
