SSC RF Institute for Biomedical Problems RAS, 76A, Khoroshevskoyoe shosse, 123007 Moscow, Russian Federation.
J Muscle Res Cell Motil. 2009 Dec;30(7-8):261-5. doi: 10.1007/s10974-010-9202-0. Epub 2010 Feb 11.
Gravitational unloading leads to destructive changes in the structure and function of muscle fibers. However, the role of the EMG activity level is still unclear. We measured changes caused by one- and three-day hypogravity in the following muscles: Soleus (Sol), Tibialis anterior (TA) and Gastrocnemius c.m. (MG). We used Wistar rats and Mongolian gerbils. The following parameters were assessed: the specific force of contraction of isolated fibers by tensometry, the transverse stiffness of the contractile apparatus by atomic force microscopy, and the calcium content by Fluo-4. We detected the accumulation of calcium ions in all muscles even after one-day unloading. In Sol this effect was more significant than in other muscles. After one-day of hypogravity we detected an increase in the specific force in all muscle types and species. Meanwhile, the transverse stiffness of the contractile apparatus, M-band and Z-disc increased only in fast muscles but not in Sol. After three-days of unloading, the specific force in Sol decreased, and the transverse stiffness of the contractile apparatus behaved in the same way as the force. The specific tension of fast muscle fibers decreased significantly in comparison with one-day unloading. In addition, the transverse stiffness of some areas of MG had a tendency to decrease in comparison to "one-day" unloading, although there was no such a tendency in the fibers of TA. In Mongolian gerbils the tendencies were the same as in the rats, but showed less dramatic changes. The reduction in the magnitude of changes in the Sol-MG-TA series correlates with EMG activity.
重力卸载会导致肌肉纤维的结构和功能发生破坏性变化。然而，肌电图（EMG）活动水平的作用仍不清楚。我们测量了以下肌肉在 1 天和 3 天低重力下的变化：比目鱼肌（Sol）、胫骨前肌（TA）和腓肠肌中间肌（MG）。我们使用了 Wistar 大鼠和蒙古沙鼠。评估了以下参数：张力法测量的分离纤维的收缩比力、原子力显微镜测量的收缩装置的横向刚度以及 Fluo-4 测量的钙含量。我们在所有肌肉中都检测到了钙离子的积累，即使在 1 天的卸载后也是如此。在 Sol 中，这种效应比其他肌肉更明显。在 1 天的低重力后，我们在所有肌肉类型和物种中都检测到了收缩比力的增加。同时，收缩装置、M 带和 Z 盘的横向刚度仅在快肌中增加，但在 Sol 中没有增加。在 3 天的卸载后，Sol 的收缩比力下降，收缩装置的横向刚度与力的变化趋势相同。与 1 天的卸载相比，快肌纤维的比张力显著下降。此外，与 1 天的卸载相比，MG 的一些区域的横向刚度有下降的趋势，尽管 TA 中的纤维没有这种趋势。在蒙古沙鼠中，趋势与大鼠相同，但变化幅度较小。Sol-MG-TA 系列中变化幅度的减小与 EMG 活动相关。
