Ammonia excretion in the Atlantic hagfish ( Myxine glutinosa ) and responses of an Rhc glycoprotein
Ammonia excretion in the Atlantic hagfish ( Myxine glutinosa ) and responses of an Rhc glycoprotein
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大西洋盲鳗（Myxine glutinosa）的氨排泄和Rhc糖蛋白的反应
DOI：
10.1152/ajpregu.00355.2014
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Walsh, Patrick J.
中科院分区：
文献类型：
--
作者：
Edwards, Susan L.;Arnold, Justin;Blair, Salvatore D.;Pray, Margaret;Bradley, Rachel;Erikson, Olivia;Walsh, Patrick J.
盲鳗是现存的最古老的颅类动物，对许多不利的环境条件表现出很高的耐受性，包括高浓度的氨。水生生物氨排泄的机制包括海蟹的囊泡性氨转运和胞吐释放机制，以及鱼类的被动氨扩散、主动氨转运和氨3或氨4+通过鳃的细胞旁渗漏机制。最近，一个新兴的范式表明恒河糖蛋白在水生无脊椎动物和脊椎动物的氨运输中起着至关重要的作用。本研究从大西洋盲鳗的鳃中鉴定出Rh糖蛋白同源物。盲鳗的Rhcg与其他脊椎动物的Rhcg具有56-60%的氨基酸同源性。利用序列信息制备抗盲鳗Rhcg （hRhcg）抗体。我们已经用hRhcg定位了鳃和皮肤上皮细胞的蛋白表达。此外，我们还量化了暴露于血浆氨水平升高后的hRhcg表达。与对照组相比，暴露于3 mmol/kg NH4Cl负荷的动物在注射后4小时内血浆氨浓度显著升高。这与注射后4小时的净氨排泄率也显著升高相关。注射后15 min和1 h，鳃和皮肤中rhhcg mRNA表达量显著升高，注射后2、4和8 h，鳃中hRhcg蛋白表达量显著升高。这些结果证明了Rhcg在大西洋盲鳗氨排泄中的潜在作用。
Hagfishes, the most ancient of the extant craniates, demonstrate a high tolerance for a number of unfavorable environmental conditions, including elevated ammonia. Proposed mechanisms of ammonia excretion in aquatic organisms include vesicular NH4+transport and release by exocytosis in marine crabs, and passive NH3diffusion, active NH4+transport, and paracellular leakage of NH3or NH4+across the gills of fishes. Recently, an emerging paradigm suggests that Rhesus glycoproteins play a vital role in ammonia transport in both aquatic invertebrates and vertebrates. This study has identified an Rh glycoprotein ortholog from the gills of Atlantic hagfish. The hagfish Rhcg shares a 56–60% amino acid identity to other vertebrate Rhcg cDNAs. Sequence information was used to produce an anti-hagfish Rhcg (hRhcg) antibody. We have used hRhcg to localize protein expression to epithelial cells of the gill and the skin. In addition, we have quantified hRhcg expression following exposure to elevated plasma ammonia levels. Animals exposed to a 3 mmol/kg NH4Cl load resulted in significantly elevated plasma ammonia concentrations compared with controls for up to 4 h postinjection. This correlated with net ammonia excretion rates that were also significantly elevated for up to 4 h postinjection. Rhcg mRNA expression in both the gill and skin was significantly elevated by 15 min and 1 h, respectively, and hRhcg protein expression in gills was significantly elevated at 2, 4, and 8 h postinjection. These results demonstrate a potential role for Rhcg in the excretion of ammonia in the Atlantic hagfish.