Potassium excretion through ROMK potassium channel expressed in gill mitochondrion-rich cells of Mozambique tilapia
Potassium excretion through ROMK potassium channel expressed in gill mitochondrion-rich cells of Mozambique tilapia
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DOI：
10.1152/ajpregu.00628.2011
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发表时间：
2012-03-01
影响因子：
2.8
通讯作者：
Kaneko, Toyoji
中科院分区：
文献类型：
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作者：
Furukawa, Fumiya;Watanabe, Soichi;Kaneko, Toyoji
Furukawa F，Watanabe S，Kimura S，Kaneko T.莫桑比克罗非鱼富含鳃囊细胞表达的ROMK钾通道的排钾作用Am J Physiol Regul Integr Comp Physiol 302：R568-R576，2012。首次发表于2011年12月28日; doi：10.1152/ajpregu.00628.2011。尽管近年来鱼类离子稳态生理学研究取得了进展，但鱼类血浆K+调节的机制仍不清楚。我们使用莫桑比克罗非鱼（一种广盐性硬骨鱼），使用一种新发明的技术不溶解并可视化从鳃排出的K+，证明了鳃富含线粒体（MR）的细胞负责K+的排泄。为了更好地了解鳃排钾的分子机制，本研究从罗非鱼中鉴定了肾外髓钾通道（ROMK）、钾离子大电导钙激活通道（K ~+-Ca 2 +-activated channel）、M亚家族（Maxi-K）、K ~+-Cl ~-共转运蛋白（KCC 1、KCC 2和KCC 4）的cDNA序列，作为参与鳃排钾的候选分子。在克隆的候选分子中，只有ROMK表现出显著的mRNA水平上调，以响应高外部K+浓度。此外，免疫荧光显微镜显示，ROMK定位于鳃MR细胞的顶端开口处，且在适应高K+浓度环境的鱼中，ROMK的免疫信号最强。为了证实通过ROMK的K+排泄，再次应用K+不溶解-可视化技术与K+通道阻断剂组合。在Ba ~（2+）存在下，K ~+沉淀被阻止，表明ROMK在K ~+排泄中起着关键作用。本研究首次证明了鱼类从鳃MR细胞中排泄K+，并且在MR细胞的顶端开口中表达的ROMK是负责K+排泄的主要分子途径。
Furukawa F, Watanabe S, Kimura S, Kaneko T. Potassium excretion through ROMK potassium channel expressed in gill mitochondrion-rich cells of Mozambique tilapia. Am J Physiol Regul Integr Comp Physiol 302: R568-R576, 2012. First published December 28, 2011; doi:10.1152/ajpregu.00628.2011.-Despite recent progress in physiology of fish ion homeostasis, the mechanism of plasma K+ regulation has remained unclear. Using Mozambique tilapia, a euryhaline teleost, we demonstrated that gill mitochondrion-rich (MR) cells were responsible for K+ excretion, using a newly invented technique that insolubilized and visualized K+ excreted from the gills. For a better understanding of the molecular mechanism of K+ excretion in the gills, cDNA sequences of renal outer medullary K+ channel (ROMK), potassium large conductance Ca2+-activated channel, subfamily M (Maxi-K), K+-Cl- cotransporters (KCC1, KCC2, and KCC4) were identified in tilapia as the candidate molecules that are involved in K+ handling. Among the cloned candidate molecules, only ROMK showed marked upregulation of mRNA levels in response to high external K+ concentration. In addition, immunofluorescence microscopy revealed that ROMK was localized in the apical opening of gill MR cells, and that the immunosignals were most intense in the fish acclimated to the environment with high K+ concentration. To confirm K+ excretion via ROMK, K+ insolubilization-visualization technique was applied again in combination with K+ channel blockers. The K+ precipitation was prevented in the presence of Ba2+, indicating that ROMK has a pivotal role in K+ excretion. The present study is the first to demonstrate that the fish excrete K+ from the gill MR cells, and that ROMK expressed in the apical opening of the MR cells is a main molecular pathway responsible for K+ excretion.