Carcinogenresistance mechanism in the small intestinal tracts

点击翻译按钮获取中文摘要

To clarify the organ specificity of the carcinogenresistance of the small bowel, a segment of the ileum was interposed in the distal colon in male wister rats. The rats were administered MNNG at a dose of 2.5 mg/day via the rectum for 2 weeks from the second postoperative week. Cell kinetic analysis of intestinal epithelium was performed by the double labeling method. Also xanthine oxidase activity of ileal and colon mucosa was measured by spectrophotometric assay in crude tissue homegenate.1. The carcinogenic rate in the interposed ileum was 3.3%, significantly lower than the 38.3% in the distal colon. Also the number of cancers per rat was 0.03 in the interposed ileum, significantly lower than 0.07 in the distal colon.2. The migration time of the MNNG-treated group was 91.4(〕SY.+-.〔)21.1 hours in the distal colon and 40.6(〕SY.+-.〔)8.2 hours in the interposed ileum.3. The epithelial cell migration time from the bottom of the crypt to the surface in the interposed ileum was significantly shorter than that in the distal colon.4. Xanthine oxidase activity for interposed ileum was sinificantly higer than that for distal colon.From these results, it was suspected that the rapid renewal rates and high xanthine oxidase activity were the principal carcinogen-resistance mechanism of the small bowel.