+Gx作用对大鼠膈肌收缩性能的影响及其机理

目的观察 +Gx作用对大鼠膈肌收缩性能的影响 ,并探讨其机理。方法 42只雄性Wistar大鼠 ,随机分成对照组 (经受 + 1Gx作用 )和实验组 (经受 + 1 5Gx/ 3min作用 )各 2 1只。分别测定膈肌张力 ,膈肌腺苷酸和乳酸含量 ,并对其超微结构进行了观察和照像。结果 1 ) +Gx作用结束后即刻与 +Gx作用前比较 ,实验组大鼠膈肌的低频张力明显降低 (P <0 .0 1 ) ,高频张力虽呈下降趋势 ,但无统计学意义 (P >0 .0 5 ) ,而对照组大鼠膈肌的张力基本保持不变 ;2 ) +Gx作用结束后即刻 ,实验组大鼠与对照组大鼠相比 ,其膈肌ATP含量减少 (P <0 .0 1 ) ,ADP、乳酸含量增加 (P <0 .0 5和P <0 .0 1 ) ,ADP/ATP和AMP/ATP的比值均明显增大 (P <0 .0 1 ) ;3) +Gx作用结束后即刻 ,实验组大鼠膈肌的线粒体和肌浆网发生了缺氧性改变 ,而对照组无此改变。结论 +Gx作用可致大鼠膈肌疲劳 ,其原因可能与 +Gx作用下缺血缺氧引起的膈肌能量代谢和超微结构的改变有关

Effects of +Gx Stress on Contractility of Rat Diaphragm and Its Mechanism

Objective To observe the effect of sustained +Gx exposure on contractility of rat diaphragm and explore its mechanism. Method Forty two male Wistar rats were randomly divided into control group (underwent +1 Gx exposure, n=21) and experiment group (underwent +15 Gx for 3 min, n=21). The tension of rat diaphragm in vivo, contents of nucleoside phosphates and lactic acid in diaphragm and ultrastructure of diaphragm were measured and observed respectively. Result 1) Compared with pre +Gx, low frequency tension of diaphragm of experiment group decreased significantly (P<0.01), whereas high frequency tension did not significantly decrease after +Gx (P>0.05). As to the control group, however, the tension of diaphragm tested at a wide range of frequencies was almost unchanged (P>0.05).2) Compared with control group, ATP decreased (P<0.01), while ADP and lactic acid contents in diaphragm increased significantly (P< 0.05 and P<0.01) after +Gx in experiment group. In addition, ratios of ADP/AMP and AMP/ATP increased significantly (P<0.01). 3) After +Gx exposure, hypoxic changes in ultrastructure of rat diaphragm occurred in experiment group, but not in control group. Conclusion Sustained +Gx exposure could cause diaphragm muscle fatigue, which was possibly due to changes in energy metabolism and ultrastructure of rat diaphragm induced by hypoxia under +Gx stress.