Ghrelin对大鼠创伤性脑损伤后胃肠功能的影响

Effect of Ghrelin on gastrointestinal motility after traumatic brain injury

目的探讨Ghrelin对创伤性脑损伤（TBI）后胃肠功能的影响。方法选取72只成年健康雄性SD大鼠，按照随机数字表法分为假手术组（8只）、TBI组（32只）和Ghrelin组（32只）。假手术组仅颅骨开窗消毒后缝合头皮，但不进行打击。TBI组腹腔注射麻醉后颅骨开窗，在骨窗中心用电子皮质损伤撞击仪以打击深度3mm、打击最低点持续时间200ms、打击速率5m／s进行打击。Ghrelin组于伤后30min经尾静脉注射Ghrelin20μg／kg。各组于伤后6，24，48，72h进行神经功能缺陷综合评分（mNSS）、胃肠大体观察；检测粪便含水量百分比、胃内容物占体重的百分比；切取胃、距回盲部15cm处小肠、回盲部（近端回肠肠管长约3em，远端3em结肠肠管长约3cm），制备电镜切片，观察胃肠黏膜微观变化。结果TBI组和Ghrelin组伤后24，48，72hmNSS均明显高于假手术组（P〈0．01）；TBI组伤后24，48，72h mNSS也均明显高于Ghrelin组（P〈0．01）。假手术组可见肠壁呈粉红色。TBI组胃扩张，壁变薄，色苍白或暗红，小肠肠腔扩张、色泽灰暗，甚至淤血，肠壁伴有大量黏液。Ghrelin组6h后较TBI组明显好转。与Ghrelin组相比，TBI组从24h开始即出现粪便含水量百分比显著减少（P〈0．05），后随着时间的推移粪便含水量百分比减少的幅度下降；并出现明显的胃排空延缓（P〈0．05），胃内容物占体重的百分比出现下降趋势（P〈0．01）。胃黏膜变化：TBI组伤后72h可见胃腺中的主细胞，细胞表面有散在的、短小的微绒毛。胞浆突出到腺腔，胞浆中可见大量粗面内质网，排列不甚规则，线粒体局部肿胀，内可见髓样小体。胞浆内可见大量内分泌颗粒，线粒体散在分布、肿胀，线粒体嵴变短变少，其内有髓样小体。Ghrelin组72h胃黏膜改变较TBI组明显好转。盲肠黏膜变化：TBI组伤后72h可见盲肠吸收上皮严重水肿，粗面内质网扩张明显，细胞内游离水间隙扩张，细胞顶部微绒毛局部减少，盲肠吸收上皮细胞顶部可见丰富的微绒毛，细胞之间可见由紧密连接、中间连接和桥粒连接构成的连接复合体。Ghrelin组伤后72h盲肠黏膜改变较TBI组明显好转。小肠黏膜变化：TBI组可见小肠吸收上皮损伤，顶部微绒毛排列紧密，局部脱落，胞浆水肿严重，粗面内质网肿胀。Ghrelin组改变较TBI组明显好转。结论Ghrelin是改善TBI后胃肠功能障碍的有效手段，Ghrelin能促进TBI大鼠的胃排空、增加肠推进率、改善TBI后胃肠道黏膜显微结构。

Objective To investigate the effect of Ghrelin on gastrointestinal motility after traumatic brain injury （TBI）. Methods A total of 72 adult male SD rats were randomly divided into sham operation group （ n = 8 ） , TBI group （ n = 32 ） and Ghrelin group （ n = 32 ） , according to the random number table. In the sham operation group, the scalp was sutured after craniotomy and sterilization, without any strike. In the TBI group, after intraperitoneal anesthesia, the skull was opened and the electric cortical contusion impactor was used to strike the center of bone window at the depth of 3 mm and the rate of 5 m/s. The duration of hitting the lowest point was 200 ms. In the Ghrelin group, 20 p,g/kg of Ghrelin was injected into the rat via the tail vein 30 minutes after injury. The modified neurologicalseverity score （mNSS）, percentage of water content in feces and percentage of gastric contents in body weight at 6, 24, 48 and 72 hours after operation in each group were measured. The stomach, the small intestine 15 cm from ileocecal junction, ileocecal junction （about 3 cm in the proximal ileal loops, about 3 cm in the distal ileal loops, and 3 cm colon loops） were taken out to prepare the electron microscopy section and observe the microscopic changes of the gastrointestinal mucosa. Results The mNSS in the TBI and Ghrelin groups was higher than that in the sham operation group after 24, 48 and 72 hours （P 〈 0.01 ）. The mNSS in the TBI group was higher than that in the Ghrelin group after 24, 48 and 72 hours （P 〈 0.01 ）. In the sham operation group, the intestinal wall was pink. In the TBI group, gastric dilatation and thinner wall with pale or dark red color were seen, and small intestine cavity expansion with dark color and even congestion were observed. There was much mucus in the intestinal wall. The Ghrelin group improved obviously than the TBI group after 6 hours. Compared with the Ghrelin group, the percentage of fecal water content in the TBI group decreased significantly after 24 hours （ P 〈 0. 05 ） , and the decrease rate dropped with time. Obvious delayed gastric emptying occurred （ P 〈 0.05 ）, and the percentage of gastric contents in body weight demonstrated downtrend. The changes of gastric mucosa were as follows ： the chief ceils in the gastric glands were observed 72 hours after TBI in the TBI group, and scattered short microvilli were seen in the cell surface. The cytoplasm protruded into the glandular cavity, and a large number of rough endoplasmic reticulum could be seen in the cytoplasm, with irregular arrangement. Medullary bodies could be seen inside the mitochondria which swelled locally. Abundant endocrine granules were seen in the cytoplasm. Mitochondria were scattered and swollen, and mitochondria cristae became shorter and fewer, which contained medullary bodies. The Ghrelin group improved obviously than TBI group after 72 hours in terms of gastric mucosa changes. With respect to cecum mucosa, in the TBI group 72 hours after TBI, severe edema of the cecum absorption epithelium, obvious dilation of the rough endoplasmic reticulum, expansion of the free water gap inside the cell, and local decrease of the microvilli at the top of the cell were observed. Abundant microvilli were seen in the cecum absorption epithelium and cell top. The connection complex composed of tight connections, intermediate connections, and bridging particle connections could be seen between cells. The Ghrelin group improved obviously than TBI group after 72 hours in terms of cecum mucosa changes. Conclusions Ghrelin can improve gastrointestinal motility and protect gastrointestinal mucosa in rats after TBI.