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目的观察败血症休克大鼠组织肾上腺髓质素(ADM)含量和中性内肽酶(NEP)的活性及其表达水平,以探讨NEP的变化在休克时组织ADM水平变化中的意义。方法盲肠结扎穿孔方法复制大鼠败血症性休克模型,采用放射免疫方法和荧光分光光度法分别检测血浆和组织的ADM含量和NEP的活性,用半定量RT-PCR和免疫组织化学法分别检测NEP的mRNA及其蛋白的组织分布。结果ADM和NEP广泛分布于大鼠的血浆和组织。休克早期,大鼠各组织ADM含量普遍高于对照组,NEP活性在心脏和小肠低于对照组,在血浆中高于对照组,在肺、肾和主动脉无明显变化。免疫组化结果显示,休克早期NEP在大鼠心脏、主动脉内膜和中膜的分布低于对照组。休克晚期,除大鼠小肠的ADM含量低于休克早期,血浆和其余组织的ADM含量均高于休克早期;与休克早期比较,NEP的活性除在大鼠肾脏无明显变化外,在血浆和其余组织均明显降低。NEP的免疫组化结果显示,休克晚期,NEP在大鼠心脏、主动脉内膜和中膜、肺和肾的分布弱于休克早期,在主动脉外膜无明显变化。RT-PCR结果显示,休克晚期大鼠心脏、主动脉、肺脏和小肠的NEPmRNA表达均显著低于对照组。结论NEP在大鼠败血症休克的不同时期和不同组织中的变化与ADM含量的变化不一致,提示休克过程中,不同组织局部的NEP对ADM含量的影响不同。
Objective To observe the activity of adrenomedullin (ADM) and the activity of neutral endopeptidase (NEP) in septic shock rats and the expression of NEP in order to investigate the significance of the changes of NEP in the changes of ADM level during shock. Methods The cecal ligation and puncture method was used to replicate the model of septic shock in rats. The contents of ADM and NEP in plasma and tissue were detected by radioimmunoassay and fluorescence spectrophotometry. The semi-quantitative RT-PCR and immunohistochemistry were used to detect the levels of NEP Tissue distribution of mRNA and its protein. Results ADM and NEP were widely distributed in the plasma and tissues of rats. At early stage of shock, the content of ADM in each group was generally higher than that in control group. The activity of NEP in heart and small intestine was lower than that in control group, higher in plasma than in control group, and no significant changes in lung, kidney and aorta. The results of immunohistochemistry showed that the distribution of early NEP in rat heart, aortic intima and media was lower than that in control group. In the late stage of shock, the ADM content in the small intestine was lower than that in the early stage of shock, and the content of ADM in the plasma and other tissues was higher than that in the early stage of shock. Compared with the early stage of shock, the activity of NEP was not significantly changed in the kidney and in the plasma Tissue were significantly reduced. NEP immunohistochemistry results showed that in the late stage of shock, the distribution of NEP in rat heart, aorta and tunica intima, and lung and kidney was weaker than that in early shock, and there was no significant change in the adventitia of aorta. The results of RT-PCR showed that the expression of NEP mRNA in the heart, aorta, lung and small intestine of rats with late shock was significantly lower than that of the control group. Conclusion The changes of NEP in different periods and different tissues of rats with septic shock are not consistent with the change of ADM content, suggesting that NEP in different tissues has different effects on ADM content during shock.