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

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. Key words: Ultra-short bowel syndrome; Enteral nutrition; Colonic compensation; Ultrastructure