间断性头高位倾斜对模拟失重大鼠肌萎缩的对抗作用

目的探讨间断性45°头高位倾斜(HUT)能否减轻或防止模拟失重大鼠后肢骨骼肌的萎缩性变化.方法将SD大鼠按体重匹配的原则随机分为同步对照(CON)、模拟失重(SUS)和模拟失重每日6 h+45°头高位倾斜(SUS+HUT)3组.4 wk后,取大鼠比目鱼肌(SOL)、腓肠肌内侧头(MG)及外侧头(LG)与趾长伸肌(EDL),并称其湿重.采用组织酶化学染色及计算机图像分析技术对骨骼肌I、Ⅱ型肌纤维横截面积(CSA)、比例,及毛细血管与肌纤维数的比值(C/F)进行定量分析.结果与CON相比,SUS大鼠后肢骨骼肌的湿重均显著减少,但各骨骼肌变化程度不一致.所有骨骼肌的C/F比值均显著降低.SUS+HUT组的变化如下:①肌肉湿重,SOL完全恢复,MG+LG部分恢复;间断HUT对抗肌萎缩的相对对抗效果分别为93.4%及34.8%.②骨骼肌I、Ⅱ型肌纤维CSA及比例,SOL完全恢复,MG部分恢复,其余骨骼肌仅有恢复趋势.③所有骨骼肌的C/F比值均得到恢复.结论本项研究表明间断HUT性能有效地对抗模拟失重所引起的后肢骨骼肌萎缩性变化,但不同骨骼肌的反应尚存在一定差异.本工作提示,应用间断性人工重力对抗失重不利影响的同时,尚应辅以其他对抗措施.

Counteracting Effects of Intermittent Head- up Tilt on Simulated-Weightlessness Induced Atrophy of Anti gravity Muscles.

Objective. To study the efficacy of intermittent + Gz (45 degrees head-up tilt, HUT) exposures in preventing or alleviating atrophic changes in hind limb muscles induced by simulated weightlessness. Method. Male Sprague-Dawley (SD) rats were assigned randomly to one of three groups: simultaneous control (CON), simulated weightlessness (SUS), and SUS plus 6 h/d HUT (SUS + HUT). Muscles examined included soleus (SOL), medial gastrocnemius (correction from grastrocnemius) (MG), lateral gastrocnemius (LG) and extensor digitorum longus (EDL). Sections were treated with an adenosinetriphosphatase (ATPase) stain or alkaline phosphatase stain. The cross-sectional areas (CSA) of fibers, the relative proportion of type I fiber and the ratio of capillaries/fibers (C/F) were measured using Leica image analysis system. Result. Compared with CON, the wet weight of hind limb muscles in SUS were significantly reduced. The changes of wet weight in different groups were various. The C/F ratios of all muscles were significantly reduced. SUS + HUT rats showed significant increases in SOL and MG wet weight, and the relative counter-effects of intermittent HUT were 93.4% and 34.8%, respectively. In SUS + HUT group, the CSA of both type I and II fibers and relative proportion of type I fibers were completely recovered in SOL, and partially recovered in MG, while the counter-effects were much less obvious in the fibers of LG and EDL. However, HUT resulted in a significant recovery of the C/F ratios in all muscles. Conclusion. The present study demonstrated that intermittent HUT is effective in counteracting the atrophy induced by simulated weightlessness. The result that reactivity to HUT varied among different muscles suggests that the intermittent artificial gravity should be complemented with other countermeasures.