Luciano L, Konitz H, Reale E
Laboratory of Cell Biology and Electron Microscopy, Hannover Medical School, Federal Republic of Germany.
Cell Tissue Res. 1989 Nov;258(2):339-47. doi: 10.1007/BF00239454.
It is generally accepted that variations in membrane cholesterol content affect the fluidity of the bilayer, thus altering its permeability. In the biological membranes, in physiological conditions, a high cholesterol content rigidifies the bilayer decreasing its permeability, a lower cholesterol content induces the opposite effect by increasing the permeability. Since differences in the epithelial permeability for short chain fatty acids have previously been demonstrated in the proximal and distal colon of the guinea pig, these two regions were investigated to establish whether differences in membrane cholesterol content of the absorbing cells can be demonstrated. Freeze-fracture replicas of filipin-treated colonic tissue were used. The results show that in the proximal colon the density of filipin cholesterol complexes located on the luminal plasma membrane of the columnar absorbing cells was significantly higher (about twice) than in the distal colon. Therefore the lower amount of cholesterol present in the membrane of the absorbing cells in the distal colon indicates a greater fluidity of the membranes of the epithelial cells in this region. Such fluidity could be correlated to the higher absorption rates of shortchain fatty acids characteristic of this region.
普遍认为，膜胆固醇含量的变化会影响双层膜的流动性，从而改变其通透性。在生物膜中，在生理条件下，高胆固醇含量会使双层膜变硬，降低其通透性，较低的胆固醇含量则会通过增加通透性产生相反的效果。由于先前已证明豚鼠近端和远端结肠对短链脂肪酸的上皮通透性存在差异，因此对这两个区域进行了研究，以确定是否能证明吸收细胞的膜胆固醇含量存在差异。使用了经菲律宾菌素处理的结肠组织的冷冻断裂复制品。结果表明，在近端结肠，位于柱状吸收细胞腔面膜上的菲律宾菌素胆固醇复合物密度明显高于（约两倍）远端结肠。因此，远端结肠吸收细胞膜中胆固醇含量较低表明该区域上皮细胞膜的流动性更大。这种流动性可能与该区域特有的短链脂肪酸较高的吸收率相关。
