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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 changes of lung morphology under brain death and its possible mechanism. Methods A total of 10 Parmesan miniature pigs were randomly divided into 2 groups: brain death group and control group. The model of brain death was established by using the slow and intermittent intracranial pressurization method. The brain death state of experimental animals was maintained by breathing and circulating support for 24 hours. The control group was only craniotomy. The levels of TNF-α, IL-1β and IL-6 in serum were determined at 3, 6, 12, 18 and 24 hours after brain death respectively. The changes of lung tissue were observed by electron microscopy. The ultrastructure of lung was observed by electron microscope. The protein kinase C (PKC-α) was detected by immunohistochemical staining. The expression of PKC-α mRNA was detected by reverse transcription polymerase chain reaction. Results The levels of IL-1β, IL-6 and TNF-α in the control group at each time point were not significantly changed. The levels of IL-1β, IL-6 and TNF-α in the brain death group were significantly higher than those in the control group With the extension of brain death time and gradually increased (P <0.05). The levels of PKC-α protein and mRNA in lung tissue were significantly higher than those in control group (P <0.05). The lung tissue of the control group showed no obvious damage change under the light microscope and the electron microscope. The structure of the brain dead animals changed obviously. The light microscopy showed that the alveolar septum widened, the alveolar cavity had exudate, the pulmonary capillary congestion, Under the electron microscope, cytoplasm of alveolar cells in euthanasia, cytoplasm of mitochondria of type Ⅱ cells in alveolar epithelium and partial lysis of mitochondria were observed under electron microscope. There was no microvilli in the lung tissue. CONCLUSION: The morphological changes of brain damage and inflammatory mediators in the lungs are induced by brain death. The marked increase of PKC-αmRNA transcription and protein translation in the lung may be one of the causes of the morphological changes in the lung.