Chasiotis Helen, Kelly Scott P
Department of Biology, York University, Toronto, ON, Canada, M3J 1P3.
J Exp Biol. 2008 May;211(Pt 10):1524-34. doi: 10.1242/jeb.014894.
Tight junctions (TJs) are an integral component of models illustrating ion transport mechanisms across fish epithelia; however, little is known about TJ proteins in fishes. Using immunohistochemical methods and Western blot analysis, we examined the localization and expression of occludin, a transmembrane TJ protein, in goldfish tissues. In goldfish gills, discontinuous occludin immunostaining was detected along the edges of secondary gill lamellae and within parts of the interlamellar region that line the lateral walls of the central venous sinus. In the goldfish intestine, occludin immunolocalized in a TJ-specific distribution pattern to apical regions of columnar epithelial cells lining the intestinal lumen. In the goldfish kidney, occludin was differentially expressed in discrete regions of the nephron. Occludin immunostaining was strongest in the distal segment of the nephron, moderate in the collecting duct and absent in the proximal segment. To investigate a potential role for occludin in the maintenance of the hydromineral balance of fishes, we subjected goldfish to 1, 2 and 4 weeks of food deprivation, and then examined the endpoints of hydromineral status, Na+,K+-ATPase activity and occludin protein expression in the gills, intestine and kidney. Occludin expression altered in response to hydromineral imbalance in a tissue-specific manner suggesting a dynamic role for this TJ protein in the regulation of epithelial permeability in fishes.
紧密连接（TJs）是阐释离子跨鱼类上皮细胞转运机制模型的一个不可或缺的组成部分；然而，关于鱼类紧密连接蛋白却知之甚少。我们运用免疫组织化学方法和蛋白质免疫印迹分析，检测了跨膜紧密连接蛋白闭合蛋白（occludin）在金鱼组织中的定位和表达。在金鱼鳃中，在次级鳃小片边缘以及中央静脉窦侧壁内衬的部分片间区域内检测到了不连续的闭合蛋白免疫染色。在金鱼肠道中，闭合蛋白以紧密连接特异性分布模式定位到肠腔柱状上皮细胞的顶端区域。在金鱼肾脏中，闭合蛋白在肾单位的不同区域差异表达。闭合蛋白免疫染色在肾单位远曲段最强，在集合管中等强度，在近曲段则无表达。为了研究闭合蛋白在维持鱼类水盐平衡中的潜在作用，我们让金鱼分别经历1周、2周和4周的饥饿处理，然后检测鳃、肠道和肾脏的水盐状态终点指标、钠钾ATP酶活性以及闭合蛋白的表达。闭合蛋白的表达因应水盐失衡而以组织特异性方式发生改变，这表明这种紧密连接蛋白在调节鱼类上皮通透性方面发挥着动态作用。
