Pantzar N, Lundin S, Wester L, Weström B R
Dept. of Animal Physiology, University of Lund, Sweden.
Scand J Gastroenterol. 1994 Aug;29(8):703-9. doi: 10.3109/00365529409092497.
The barrier properties of the small intestine were investigated by studying the bidirectional permeability to five commonly used marker molecules.
Proximal and distal small-intestinal segments from rats were mounted in diffusion chambers, and the permeation of the markers 3H-mannitol (Mw 182), 51Cr-ethylenediamineteraacetic acid (Mw 341), [mercaptopropionic acid], D-arginine8]-vasopressin (Mw 1069), fluorescein isothiocyanate (FITC)-dextran (mean Mw 3000), and inulin (Mw 5200) was measured across the mucosa in both directions.
A generally increased inward (mucosa to serosa) and a decreased outward (serosa to mucosa) permeation of the markers was found in the proximal to distal direction. The inward permeability showed increasing regional differences with decreasing size of the markers. In the absence of the villous epithelium, removed by scraping the intestinal wall, 86% to 62% of the proximal and distal barrier was lost in the inward direction but only 14% to 26% in the outward direction.
The intestinal epithelial barrier is more permeable in the outward than in the inward direction, and regional permeability differences exist in a size-dependent fashion. The results suggest two passage routes, one for the smallest molecule, mannitol, and a second for the larger markers in the present size range, both apparently different from the route for macromolecules such as intact proteins.
通过研究对五种常用标记分子的双向通透性来调查小肠的屏障特性。
将大鼠的近端和远端小肠段安装在扩散室中，测量标记物³H-甘露醇（分子量182）、⁵¹Cr-乙二胺四乙酸（分子量341）、[巯基丙酸]、[D-精氨酸⁸]-加压素（分子量1069）、异硫氰酸荧光素（FITC）-葡聚糖（平均分子量3000）和菊粉（分子量5200）在黏膜两侧的双向通透情况。
在近端到远端方向上，发现标记物的向内（黏膜到浆膜）通透总体增加，向外（浆膜到黏膜）通透减少。随着标记物尺寸减小，向内通透性的区域差异增大。在刮除肠壁去除绒毛上皮后，近端和远端屏障的向内方向丧失了86%至62%，而向外方向仅丧失了14%至26%。
肠上皮屏障向外的通透性高于向内，并且存在大小依赖性的区域通透性差异。结果提示存在两条通道，一条用于最小的分子甘露醇，另一条用于当前尺寸范围内较大的标记物，两者显然都不同于完整蛋白质等大分子的通道。
