巴马小型猪脑死亡状态下的肺脏形态变化及其机制

An experimental study on how brain-dead state affects the lung morphology of Ba-Ma mini pigs and the mechanism

目的探讨脑死亡状态下肺脏形态变化及可能的机制。方法巴马小型猪10只,随机分为2组,即脑死亡组与对照组。应用改进的缓慢间断颅内加压法建立脑死亡模型,通过呼吸、循环支持维持实验动物脑死亡状态24h,对照组仅行开颅。分别测定脑死亡后第3、6、12、18和24h时血清中肿瘤坏死因子(TNF-α)、白细胞介素1(IL-1β)及IL-6水平;脑死亡后24h时取肺脏组织,HE染色观察肺脏组织变化,电镜观察肺脏超微结构变化,免疫组化染色观察蛋白激酶C(PKC-α)的表达水平,逆转录聚合酶链反应检测PKC-αmRNA的表达水平。结果对照组各检测时点的IL-1β、IL-6、TNF-α水平变化不明显,脑死亡组血清IL-1β、IL-6、TNF-α明显高于对照组(P<0.05),并随脑死亡时间的延长而逐渐升高(P<0.05)。肺组织中PKC-α蛋白及其mRNA水平明显高于对照组(P<0.05)。对照组的肺组织在光镜及电镜下未见明显的损伤性变化,脑死亡组动物的组织结构发生明显改变,光镜下可见肺泡间隔增宽,肺泡腔有渗出液,肺毛细血管充血,肺组织中有淋巴细胞浸润;电镜下,脑死亡组的肺泡细胞胞质水肿,肺泡上皮Ⅱ型细胞线粒体肿胀,线粒体部分膜溶解等改变,微绒毛缺失。结论脑死亡状态导致肺脏出现损伤性形态学变化,机体炎症介质水平升高;肺脏中PKC-αmRNA转录和蛋白翻译水平明显升高可能是肺脏发生损伤性形态学变化的原因之一。

Objective To investigate the change of lung morphology and the mechanism in the brain-dead state. Methods Ten Ba-Ma mini pigs were randomized into 2 groups： brain-dead group （group B, n = 5） and control group （group C, n = 5）. Brain-dead model was established in group B by increasing intracranial pressure in a modified, slow and intermittent way, and brain-dead state maintained for 24 h by respiration and circulation support. The serum TNF-a, IL-1β, and IL-6 were determined at 3, 6 12, 18 and 24 h after the initial confirmation of brain death. Lung tissues were taken at 24 h. The alterations of lung tissues were observed by HE staining, and the expression of PKC-α de tected by immunohistochemistry. PKC-α mRNA at crostructure of hepatic tissues was observed under light microscopy, broadened lung alveolar septum, each time point was detected by RT PCR. The mi an electron microscope. Results （1） Under the edematous, extravasate in the alveolar congestive capillary vessel, infiltration of lymphocyte were observed. Under the election microscopy, cytoplasm edema, swollen mitochondria of the type-Ⅱ epithelial ceils, partial membrane dissolution of mitochondria were observed and the mierotomentum disappeared. No obvious morphological injury was ob served under light microscopy and election microscopy. （2） Compared with control group, the serum IL-1β, IL-6 and TNF-α in brain-dead group began to increase at 3 h after brain death, and become more and more higher when the maintained state was prolonged. The expression of PKC-α and PKC-α mRNA in brain-dead group was increased at 24 h in the lung tissue. Conclusion Brain death may evoke lung morphological injury and increase the level of inflammatory mediators; After brain death the levels of PKC-α mRNA transcription and protein translation is increased. The activation of PKCa and the alteration of inflammatory mediators are supposed to be one of the mechanisms of the lung injury.