Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
J Exp Biol. 2015 Apr 15;218(Pt 8):1244-51. doi: 10.1242/jeb.113118. Epub 2015 Feb 26.
Acid-sensing ion channels (ASICs) are epithelial Na(+) channels gated by external H(+). Recently, it has been demonstrated that ASICs play a role in Na(+) uptake in freshwater rainbow trout. Here, we investigate the potential involvement of ASICs in Na(+) transport in another freshwater fish species, the zebrafish (Danio rerio). Using molecular and histological techniques we found that asic genes and the ASIC4.2 protein are expressed in the gill of adult zebrafish. Immunohistochemistry revealed that mitochondrion-rich cells positive for ASIC4.2 do not co-localize with Na(+)/K(+)-ATPase-rich cells, but co-localize with cells expressing vacuolar-type H(+)-ATPase. Furthermore, pharmacological inhibitors of ASIC and Na(+)/H(+)-exchanger significantly reduced uptake of Na(+) in adult zebrafish exposed to low-Na(+) media, but did not cause the same response in individuals exposed to ultra-low-Na(+) water. Our results suggest that in adult zebrafish ASICs play a role in branchial Na(+) uptake in media with low Na(+) concentrations and that mechanisms used for Na(+) uptake by zebrafish may depend on the Na(+) concentration in the acclimation medium.
酸感应离子通道（ASICs）是由细胞外 H+门控的上皮钠离子通道。最近，研究表明 ASICs 在淡水虹鳟鱼的钠离子摄取中发挥作用。在这里，我们研究了 ASICs 是否参与了另一种淡水鱼类，斑马鱼（Danio rerio）的钠离子转运。使用分子和组织学技术，我们发现 asic 基因和 ASIC4.2 蛋白在成年斑马鱼的鳃中表达。免疫组织化学显示，ASIC4.2 阳性的富含线粒体的细胞与富含 Na+/K+-ATPase 的细胞不同，而是与表达液泡型 H+-ATPase 的细胞共定位。此外，ASIC 和 Na+/H+- exchanger 的药理学抑制剂显著降低了暴露于低 Na+ 培养基中的成年斑马鱼对 Na+的摄取，但对暴露于超低 Na+水中的个体没有相同的反应。我们的结果表明，在成年斑马鱼中，ASICs 在低 Na+浓度的培养基中发挥了鳃部钠离子摄取的作用，并且斑马鱼用于摄取 Na+的机制可能取决于适应培养基中的 Na+浓度。
