The obscure puffer Takifugu obscurus is a euryhaline fish species suitable for studying the molecular mechanism of osmoregulation. The distributional changes of branchial ionocytes were detected following the transfer from freshwater (FW) to seawater (SW) based on two main ion transporters, Na+/K+-ATPase (NKA) and Na+/K+/ 2Cl− cotransporter 1 (NKCC1). The mRNA and protein expression levels of NKA and NKCC1 in the gills all increased rapidly in the first four days after transfer to SW. Double immunofluorescence staining showed that NKCC1 and NKA were colocalized in the branchial ionocytes and the immunoreaction of NKCC1 was stronger after transfer. Moreover, following transfer to SW, the number of lamellar ionocytes in the gills is reduced and the number of filament ionocytes is increased significantly. Taken together, these findings indicated that SW transfer of obscure puffer promotes the changes of distribution, function and size of branchial ionocytes.

中文翻译：

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广盐暗河豚、Takifugu obscurus从淡水转移到海水后鳃离子细胞的免疫组织化学特征和位置变化

无名河豚 Takifugu obscurus 是一种广盐性鱼类，适合研究渗透压调节的分子机制。基于两种主要离子转运蛋白 Na+/K+-ATPase (NKA) 和 Na+/K+/ 2Cl- 协同转运蛋白 1 (NKCC1) 从淡水 (FW) 转移到海水 (SW) 后检测到鳃离子细胞的分布变化。在转移到SW后的前4天，鳃中NKA和NKCC1的mRNA和蛋白质表达水平均迅速增加。双免疫荧光染色显示NKCC1和NKA共定位于鳃离子细胞内，转移后NKCC1的免疫反应更强。此外，转移到 SW 后，鳃中的层状离子细胞数量减少，而丝状离子细胞的数量显着增加。综合起来，