The dendritic organ (DO) is a salt secretory organ in the Plotosidae marine catfishes. The potential role of the DO in ammonia excretion was investigated by examining the effects of salinity [brackishwater (BW 3‰), seawater (SW 34‰) and hypersaline water (HSW 60‰)] acclimation and DO ligation on ammonia excretion and ammonia transporter expression by immunohistochemistry (IHC), immunoblotting (IB) and qPCR. Ammonia flux rates (JAmm) were significantly lower in BW compared to SW and HSW. DO ligation resulted in a significantly lower JAmm in SW but not BW fish. IHC demonstrated apical and basolateral localization of Rhesus-associated glycoprotein (Rhag-like) and Rhbg-like proteins, respectively, in parenchymal cells of the DO acini. In the gills, which are the primary site of ammonia excretion in teleost fishes, IHC showed an apical localization of Rhag-like protein in some Na+/K+-ATPase (NKA) immunoreactive (IR) cells limited to a few interlamellar regions of the filament and, in both apical and basolateral membranes of pillar cells irrespective of treatment group. In gills, the distribution of NKA-IR cells showed no salinity and/or ligation dependency. IB of Rhag and Rhbg-like proteins was found only in the gills and expression levels did not change with salinity but ligation in BW decreased Rhbg-like levels. Although Rhcg was not detected with heterologous antibodies, rhcg1 mRNA expression was detected in both gills and DO. HSW was associated with the lowest expression in DO and ligations in SW and BW were without effect on branchial expression levels. Taken together these results indicate the DO potentially has a physiological role in ammonia excretion under SW conditions.

中文翻译：

---

条纹鳗cat鱼的纹状体器官是氨分泌器官吗？

树突器官（DO）是P科海洋cat鱼中的一种盐分泌器官。通过研究盐度[咸水（咸水（BW 3‰），海水（SW 34‰）和高盐水（HSW 60‰）]驯化和DO结扎对氨排泄和氨转运的影响，研究了DO在氨排泄中的潜在作用。通过免疫组织化学（IHC），免疫印迹（IB）和qPCR进行表达。与SW和HSW相比，BW中的氨通量率（JAmm）显着降低。DO结扎可显着降低SW的JAmm，但不会降低BW鱼。IHC在DO acini的实质细胞中分别显示了恒河猴相关糖蛋白（Rhag样）和Rhbg样蛋白的根尖和基底外侧定位。tele是硬骨鱼氨排泄的主要场所，IHC在某些Na + / K + -ATPase（NKA）免疫反应（IR）细胞中显示了Rhag样蛋白的顶端定位，该细胞仅限于细丝的少数层间区域，并且在柱状细胞的顶膜和基底外侧膜中均不受治疗组的影响。在g中，NKA-IR细胞的分布没有盐度和/或结扎依赖性。仅在the中发现了Rhag和Rhbg样蛋白的IB，表达水平并没有随盐度的变化而变化，但在BW中的连接降低了Rhbg样水平。尽管未用异源抗体检测到Rhcg，但在g和DO中均检测到rhcg1 mRNA表达。HSW与DO中最低的表达相关，而SW和BW中的连接对分支表达水平没有影响。