Identification of intestinal bicarbonate transporters involved in formation of carbonate precipitates to stimulate water absorption in marine teleost fish
Identification of intestinal bicarbonate transporters involved in formation of carbonate precipitates to stimulate water absorption in marine teleost fish
复制标题
DOI：
10.1152/ajpregu.00759.2007
复制
发表时间：
2008-04-01
影响因子：
2.8
通讯作者：
Hirose, Shigehisa
中科院分区：
文献类型：
--
作者：
Kurita, Yukihiro;Nakada, Tsutomu;Hirose, Shigehisa
海洋硬骨鱼沉淀二价阳离子作为碳酸盐沉积物在肠道中，以最大限度地减少过量Ca 2+进入的可能性，并通过降低管腔渗透压来刺激水的吸收。因此，这种碳酸盐存款的形成有助于维持海水（SW）环境中的钙调节，并需要控制HCO 3-的分泌，以匹配进入肠腔的Ca 2+的量。尽管它的生理重要性，HCO 3-分泌的过程还没有在分子水平上的特点。我们分析了两个家庭的HCO 3-转运蛋白，Slc 4和Slc 26，在淡水和SW-驯化广盐性河豚，暗纹东方鲀（暗纹东方鲀）的表达，并获得了以下候选克隆：NBCe 1（Na+ -HCO 3- cotransporter）和Slc 26 a6 A和Slc 26 a6 B（推定的Cl-/HCO 3- exchangers）。在非洲爪蟾卵母细胞中的异源表达表明，Slc 26 a6 A和Slc 26 a6 B作为产电Cl-/nHCO（3）（-）交换体具有有效的HCO 3-转运活性，而mefugu NBCe 1作为产电Na+-nHCO（3）（-）共转运体发挥功能。NBCe 1和Slc 26 a6 A的表达在SW中的肠中被高度诱导，Slc 26 a6 B的表达在SW和淡水中的肠中被高度诱导，这表明它们参与HCO 3-分泌和碳酸盐沉淀形成。免疫组织化学染色显示顶端（Slc 26 a6 A和Slc 26 a6 B）和基底侧（NBCe 1）膜的肠上皮细胞在SW。因此，我们提出了一种机制，HCO 3运输跨肠上皮细胞的海鱼，包括基底侧HCO 3吸收（NBCe 1）和顶端HCO 3分泌（Slc 26 a6 A和Slc 26 a6 B）。
Marine teleost fish precipitate divalent cations as carbonate deposits in the intestine to minimize the potential for excessive Ca2+ entry and to stimulate water absorption by reducing luminal osmotic pressure. This carbonate deposit formation, therefore, helps maintain osmoregulation in the seawater (SW) environment and requires controlled secretion of HCO3- to match the amount of Ca2+ entering the intestinal lumen. Despite its physiological importance, the process of HCO3- secretion has not been characterized at the molecular level. We analyzed the expression of two families of HCO3- transporters, Slc4 and Slc26, in fresh-water and SW-acclimated euryhaline pufferfish, mefugu (Takifugu obscurus), and obtained the following candidate clones: NBCe1 (an Na+ -HCO3- cotransporter) and Slc26a6A and Slc26a6B (putative Cl-/HCO3- exchangers). Heterologous expression in Xenopus oocytes showed that Slc26a6A and Slc26a6B have potent HCO3--transporting activity as electrogenic Cl-/nHCO(3)(-) exchangers, whereas mefugu NBCe1 functions as an electrogenic Na+-nHCO(3)(-) cotransporter. Expression of NBCe1 and Slc26a6A was highly induced in the intestine in SW and expression of Slc26a6B was high in the intestine in SW and fresh water, suggesting their involvement in HCO3- secretion and carbonate precipitate formation. Immunohistochemistry showed staining on the apical (Slc26a6A and Slc26a6B) and basolateral (NBCe1) membranes of the intestinal epithelial cells in SW. We therefore propose a mechanism for HCO3- transport across the intestinal epithelial cells of marine fish that includes basolateral HCO3- uptake (NBCe1) and apical HCO3- secretion (Slc26a6A and Slc26a6B).