Morcos Y, Hosie M J, Bauer H C, Chan-Ling T
Department of Anatomy and Histology, Institute for Biomedical Research, University of Sydney, Sydney, NSW 2006, Australia.
J Neurocytol. 2001 Feb;30(2):107-23. doi: 10.1023/a:1011982906125.
The distributions of occludin and claudin-1, two tight junction-associated integral membrane proteins were investigated by immunohistochemical analysis of whole-mount preparations of the blood vessels in the myelinated streak of the rabbit retina. Light microscopy revealed that occludin and claudin-1 immunoreactivities were abundant along the interface of adjacent endothelial cells of all blood vessels. Electron microscopy revealed that both proteins were distributed in a regular pattern (at regular intervals of approximately 80 nm) along the length of tight junctions, probably in the regions of tight junction strands. No other structures or cell types expressed either of these two proteins in the myelinated streak. Whereas occludin immunoreactivity was concentrated only at the tight junction interface, claudin-1 immunoreactivity also extended into the cytoplasm of the endothelial cells, suggesting a different structural role for claudin-1 than for occludin at tight junctions. Retinal pigment epithelial cells expressed occludin around their entire circumference, consistent with the function of these cells as a barrier separating the retina from the leaky vessels of the choroid. Also consistent with the association of occludin expression with vessels that exhibit functional tight junctions, this protein was expressed at only a low level in, and showed an irregular distribution along, the vessels of the choroid, a vascular bed that lacks blood-barrier properties. Further, the distribution of occludin was examined during formation and remodelling of the rat retinal vasculature. Occludin expression was evident at the leading edge of vessel formation and was found on all vessels in both the inner and outer vascular plexus. Numerous vascular segments at the early stage of vascular formation and regression lost occludin expression. The biological significance of this transient loss of occludin expression in terms of barrier function remains to be elucidated.
通过对兔视网膜有髓神经纤维层血管整装标本进行免疫组织化学分析，研究了两种紧密连接相关的整合膜蛋白闭合蛋白（occludin）和Claudin-1的分布情况。光学显微镜显示，在所有血管相邻内皮细胞的界面处，闭合蛋白和Claudin-1免疫反应性丰富。电子显微镜显示，这两种蛋白沿紧密连接的长度呈规则分布（间隔约80nm），可能位于紧密连接链区域。在有髓神经纤维层中，没有其他结构或细胞类型表达这两种蛋白中的任何一种。闭合蛋白免疫反应性仅集中在紧密连接界面，而Claudin-1免疫反应性还延伸至内皮细胞的细胞质中，这表明Claudin-1在紧密连接中的结构作用与闭合蛋白不同。视网膜色素上皮细胞在其整个圆周周围表达闭合蛋白，这与这些细胞作为将视网膜与脉络膜渗漏血管分隔开的屏障的功能一致。同样与闭合蛋白表达与具有功能性紧密连接的血管的关联一致，该蛋白在脉络膜血管（缺乏血屏障特性的血管床）中仅低水平表达且分布不规则。此外，在大鼠视网膜血管系统的形成和重塑过程中检查了闭合蛋白的分布。闭合蛋白表达在血管形成的前沿很明显，并且在内、外血管丛的所有血管上都有发现。在血管形成和消退的早期阶段，许多血管段失去了闭合蛋白表达。这种闭合蛋白表达的短暂丧失在屏障功能方面的生物学意义仍有待阐明。
