内毒素血症大鼠膈肌功能障碍和肌浆网钙泵基因表达的变化

摘要

Objective To investigate endotoxemia inducing the changes of diaphragm dysfunction and gene expression in sarcoplasmic reticulum calcium pump in rats. Methods Rats were given saline (0. 5 ml ip, saline control group) and endotoxin (12 mg/kg ip, en-dotoxin group) respectively. Animals were killed at 24, 48 and 96 hours after injections. Assessments were made of the diaphragm contractility, such as peak twitch tension (Pt) , maximum tetanic tension (Po) , time to peak contraction (CT) , half relaxation time ( 1/2RT) and diaphragm force-frequency relationships, and the change of the ultrastructures and the content of sarcoplasmic reticulum calcium pump (SERCA mRNA) was analyzed by reverse transcriptase polymerize chain reactive. Results Compared with control group, Pt and Po of endotoxin group were lower (P <0. 01) , CT and 1/2RT of endotoxin group were significantly longer (P <0. 01) ; Tetanic force under the stimulus frequency of 10, 20, 40, 60, 100 Hz in endotoxin group were decreased significantly (P<0. 01). Transmission electron microscopic morphometry of diaphragm in endotoxin group revealed diaphragm myoneme confused and broken, sarcoplasmic reticulum was distended, the quantity of mitochondria was decreased, mitochondria edema and expanded, its cristae broken and vague, a great quantity of mitochondria vacuolization or vesiculation. The expression of SERCA mRNA in diaphragm was lower in endotoxin group than that of control group (P < 0.01). Conclusions Endotoxin destroys the diaphragmatic ultrastructure and induces diaphragmatic dysfunction, it could also decrease SERCA mRNA contents.%目的 探讨内毒素血症大鼠膈肌功能和膈肌肌浆网钙泵基因(SERCA)表达的变化.方法 直接采用腹腔注射内毒素12 mg/kg建立大鼠内毒素血症模型,32只成年雄性SD大鼠随机分成四组:生理盐水对照组和内毒素24 h组,48 h组,96 h组,即分别在注射内毒素24、48、96 h后处死大鼠,应用体外灌流大鼠膈肌条的方法,分别测量其单收缩张力(Pt)、最大强直张力(Po)、峰值收缩时间(CT)、半舒张时间(1/2RT)、张力-频率曲线,电镜观察大鼠膈肌超微结构,采用RT-PCR检测大鼠膈肌SERCA mRNA表达.结果 大鼠膈肌的各项力学指标:单收缩张力和最大强直张力,内毒素血症组较对照组明显降低(P＜0.01)；单收缩的峰值收缩时间和半舒张时间,内毒素血症组较对照组明显延长(P＜0.01)；在给予大鼠膈肌条10、20、40、60、100 Hz刺激时,内毒素血症组的大鼠膈肌各频率下的收缩张力明显低于对照组(P＜0.01)；超微结构显示内毒素对大鼠膈肌组织损伤明显,肌纤维断裂,肌浆网扩张,线粒体水肿,数目减少,脊断裂,空泡化或囊泡化；RT-PCR检测实验结果提示内毒素血症大鼠膈肌SERCA表达较对照组明显降低(P＜0.01).结论 内毒素可损伤大鼠膈肌超微结构,导致膈肌收缩和舒张功能障碍,并引起膈肌SERCA基因表达明显降低.