Caldwell R B
Curr Eye Res. 1987 Mar;6(3):515-26. doi: 10.3109/02713688709025208.
We have previously found that a breakdown of tight junctions in retinal pigment epithelial cells of Royal College of Surgeons' rats is associated with a redistribution of intramembrane particles and Na-K-ATPase activity. Changes in the lipid and sterol composition of membranes can alter their fluidity, permeability and enzyme activity, and may contribute to changes in cell barrier function in the dystrophic epithelium. We have now used filipin and digitonin, which bind to membrane sterols and produce membrane deformations recognizable by freeze-fracture and thin-section electron microscopy, to study the distribution of cholesterol and related 3-B-hydroxysterols in the dystrophic epithelium. The results of these studies show that in the normal pigment epithelium and prior to tight junction breakdown in the dystrophic epithelium, filipin- and digitonin-sterol complexes are rare in the membranes between tight junctions and adhering junctions, and in areas of attachment between the plasma membrane and basal lamina. Complexes are more numerous in the basal infoldings, and most densely packed in the lateral and apical microvillous membranes. During junction breakdown, complexes increase substantially in apical, basal, junctional, and nuclear membranes. Later, after the junctions disappear, complexes decrease. These results indicate that alterations in the expression of membrane sterols accompany the changes in structure and function of tight junctions in the dystrophic retinal pigment epithelium.
我们之前发现，皇家外科学院大鼠视网膜色素上皮细胞紧密连接的破坏与膜内颗粒的重新分布以及钠钾ATP酶活性有关。膜脂质和固醇成分的变化可改变其流动性、通透性和酶活性，并可能导致营养不良上皮细胞屏障功能的改变。我们现在使用制霉菌素和洋地黄皂苷，它们与膜固醇结合并产生可通过冷冻断裂和超薄切片电子显微镜识别的膜变形，以研究营养不良上皮细胞中胆固醇和相关3-β-羟基固醇的分布。这些研究结果表明，在正常色素上皮以及营养不良上皮紧密连接破坏之前，紧密连接和黏着连接之间的膜、质膜与基膜附着区域中，制霉菌素和洋地黄皂苷-固醇复合物很少见。复合物在基底褶中较多，在外侧和顶端微绒毛膜中最为密集。在连接破坏期间，复合物在顶端、基底、连接和核膜中大量增加。之后，连接消失后，复合物减少。这些结果表明，膜固醇表达的改变伴随着营养不良性视网膜色素上皮紧密连接结构和功能的变化。
