中文摘要：

目的 评价机械牵张预处理对机械通气性牵张致肺泡Ⅱ型上皮细胞损伤的影响.方法 采用随机数字表法,将体外培养的A549细胞分为6组（n=5）：对照组（Ⅰ组）、机械通气性牵张组（Ⅱ组）和不同时间机械牵张预处理组（Ⅲ组-Ⅵ组）.Ⅰ组常规培养;Ⅱ组给予20％应变率的机械牵张6h;Ⅲ组-Ⅵ组给予5％应变率的机械牵张,分别牵张15、30、60和120 min后,将应变率调整为20％牵张6h.机械牵张频率0.3 Hz,载入波形为正弦波.机械通气性牵张加载结束后,采用流式细胞仪测定细胞凋亡情况,计算细胞凋亡率;采用流式细胞仪测定纤维状肌动蛋白（F-actin）表达.结果 与Ⅰ组比较,Ⅱ组细胞凋亡率升高,F-actin表达上调（P＜0.05）;与Ⅱ组比较,Ⅳ组-Ⅵ组细胞凋亡率降低,Ⅴ组和Ⅵ组F-actin表达上调（P＜0.05）.结论 机械牵张预处理（30～ 120 min）可减轻机械通气性牵张致肺泡Ⅱ型上皮细胞损伤.

英文摘要：

Objective To evaluate the effects of mechanical stretch preconditioning on pathological stretch-induced damage to type Ⅱ alveolar epithelial cells.Methods A549 cells cultured in vitro were randomly divided into 6 groups （n =5 each）using a random number table：control group （Ⅰ group）,pathological stretch group （Ⅱ group） and different time mechanical stretch preconditioning ＋ pathological stretch group （group Ⅲ-Ⅵ）.A549 cells were exposed to 20% cyclic stretch at 0.3 Hz for 6 h in Ⅱ group.In Ⅲ-Ⅵ groups,A549 cells were exposed to 5% cyclic stretch at 0.3 Hz for 15,30,60 and 120 min,respectively,and then exposed to 20% cyclic stretch at 0.3 Hz for 6 h.After the end of pathological stretch,the apoptosis in cells was detected using flow cytometry and was calculated.F-actin expression was determined using flow cytometry.Results Compared with group Ⅰ,the apoptosis rate was significantly increased,and the expression of F-actin was up-regulated in Ⅱ group.Compared with group Ⅱ,the apoptosis rate was significantly increased in groups Ⅳ-Ⅵ,and the expression of F-actin was up-regulated in groups Ⅴ and Ⅵ.Conclusion Preconditioning with mechanical stretch （30-120 min） can mitigate pathological stretch-induced damage to type Ⅱ alveolar epithelial cells.