控制通气对大鼠膈肌组织形态学及肌球蛋白重链的影响

目的探讨控制通气(CMV)对大鼠膈肌组织形态学的影响,以阐明机械通气膈肌功能异常的机制。方法观察18h和24hCMV后大鼠膈肌超微结构及HE染色的结构改变,并检测膈肌肌球蛋白重链(MHC)表型和肌纤维横截面积(CSA)。结果 24hCMV组膈肌纤维损伤密度远高于对照组(P<0.01),肌纤维形状不规则、肌纤维萎缩及结构松散,18hCMV组仅轻度改变;24hCMV组膈肌MHCfast比率升高,MHCslow比率有下降趋势但无统计学差异;MHCfast和MHCslow肌纤维CSA及MHCfast和MHCslow蛋白表达均降低(P均<0.05);18hCMV组两种肌纤维的阳性比率、肌纤维CSA及MHCfast和MHCslow的蛋白表达均无改变。24hCMV组肌纤维的损伤密度与MHCfast阳性比率呈正相关(P<0.05)。结论短期CMV可造成膈肌损伤、肌纤维萎缩,以及慢肌向快肌的移行改变。CMV所造成的肌肉损伤与适应性改变可能相关联。

Effects of mechanical ventilation on morphological properties and myosin heavy chain of diaphragm fibers in rats

Objective To clarify the mechanisms of mechanical ventilation-induced diaphragm dysfunction by exploring the effects of control mechanical ventilation(CMV) on the morphology of rat diaphragm.Methods Biopsy specimens were taken from the diaphragm after 18 h and 24 h CMV for electron microscopy and HE staining to assess muscle fiber injury;myosin heavy chain(MHC) expression and cross section area(CSA) were determined by immunohistochemistry.Results Compared with that in the control group,the density of muscle injury was significantly higher in 24 h CMV group(P<0.01),and muscle fibers had irregular shape,atrophy and loose structure.Only slight changes occurred in 18 h CMV group.The positive rate of MHCfast significantly increased,but that of MHCslow tended to decrease.CSA and protein expressions of different MHC isoforms in the diaphragm were decreased(both P<0.05).In 18 h CMV group,the positive rate,muscle fiber CSA as well as protein expression of MHC MHCfast or MHCslow did not alter.The density of muscle injury was positively correlated with the positive rate of MHCfast in 24 h CMV group(P<0.05).Conclusion Muscle injury,muscle atrophy,and the shift of muscle fibers from slow to fast in the diaphragm occur after short-term CMV.The muscle injury may stimulate adaptive alteration of the diaphragm for improvement of muscle function.