超短肠大鼠结肠代偿的细胞超微结构变化

Observation of ultrastructure and absorption function of colon mucosa in rats with ultra-short bowel syndrome

目的 观察超短肠大鼠结肠黏膜细胞超微结构和吸收功能的变化.方法 将30只雄性SD大鼠随机分为超短肠组（手术切除大鼠90%～95%的小肠）、假手术组和正常对照组,每组10只.给予肠内营养支持21 d后,采用扫描电镜观察结肠黏膜表画形态,透射电镜观察结肠黏膜上皮细胞超微结构变化.用D-木糖溶液和15N-甘氨酸对结肠进行封闭式连续循环灌注3 h,测定结肠对水、碳水化合物、氨基酸的吸收情况.结果 透视电镜观察结果显示,超短肠组大鼠较正常大鼠的结肠黏膜杯状细胞减少,吸收上皮细胞增多,微绒毛变长变密,细胞膜表面积增加,细胞间连接明显增多,桥粒、紧密连接和缝隙连接较多,内质网和高尔基体发达,线粒体数量明显增多.扫描电镜观察结果显示,超短肠组大鼠较正常大鼠的结肠皱襞深度增加,黏膜增厚,隐凹开口明显增多;隐凹内微绒毛样结构数目明显增多,长度增长且密度增加.超短肠组大鼠结肠对水的吸收能力明显高于假手术组和正常对照组（P均=0.000）;1、2、3 h内木糖吸收率和15N-甘氨酸吸收率均明显高于假手术组和正常对照组（P均＜0.01）.结论 超短肠大鼠结肠吸收能力可代偿增强.结肠黏膜细胞凋亡减少、吸收细胞增多、微绒毛增生、细胞膜表面积增加和线粒体增多可能是其物质和能量基础.

Objective To observe the ultrastructure and absorption function of colon mucosa in rat with ultra-short bowel syndrome. Methods Totally 30 SD rats were randomly divided into three groups： ultra-short bowel group （90%-95% of the intestine was surgically resected, n = 10）, sham group （n = 10）, and normal control group （n = 10）. All animals were given with enteral nutrition. Scanning electron microscopy was performed 21 days later to observe the morphology of mucosal surface, and transmission electron microscopy was performed to observe the ultrastructural changes of intestinal epithelial cells. The absorption of colon to water, carbohydrates, and amino acid determined after 3 hours of closed perfusion of the colon with D-xylose solution and 15N-glycine on the continuous cycle of colon. Results As shown by the transmission electron microscopy, compared with the normal control group, rats in the ultra-short bowel group showed significantly decreased goblet cells on colonic mucosl surface, increased epithelial cells, longer and denser microvillus, increased area of membrane surface, increased number of cell-cell junctions, increased number of desmosome, tight junction, and gap junctions, higher development of endoplasmic reticulum and dictyosome, and increased number of mitochondria. As shown in the screening electron microscopy, compared with the normal rats, rats in the ultra-short bowl group had significantly deeper colon folds, thicker mucous membrane, increased number of bay openings, and longer and denser microvillus-like structures inside bays. The capability of water absorption was signicatnly higher in the ultra-short bowl group than in the sham group and normal control group （P = 0. 000） . The absorption rates of xylose and 15 N-glycine were also significantly higher in the ultra-short bowl group than in the control group （P 〈 0. 01）. Conclusions The absorption capability can be compensatively increased in rats with ultra-short bowel syndrome. Decreased apoptosis of colon mucosa cells, increased absorption cells, hyperplasia of microvilli, increased area of the membrane surface,and increased number of mitochondria may constitute its material and energy bases.