Ammonium transport in the colonic crypt cell line, T84: role for Rhesus glycoproteins and NKCC1.
Ammonium transport in the colonic crypt cell line, T84: role for Rhesus glycoproteins and NKCC1.
复制标题
结肠隐窝细胞系 T84 中的铵转运：恒河猴糖蛋白和 NKCC1 的作用。
DOI：
10.1152/ajpgi.00251.2006
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Matthews,JeffreyB
中科院分区：
文献类型：
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作者：
Worrell,RogerT;Merk,Lisa;Matthews,JeffreyB
虽然结肠腔NH 4+水平很高，在人类中为15-44 mM正常范围，但相对较少的研究涉及NH 4+的转运机制。更广泛的研究已经阐明了NH 4+在肾脏集合管中的转运，其涉及也存在于远端结肠中的许多转运过程。类似于肾集合管中的NH 4+分泌，我们表明远端结肠分泌模型，T84细胞系，具有分泌NH 4+并维持顶部至基底侧NH 4+梯度的能力。NKCC 1、Na+-K+-ATPase和NH 4+转运蛋白RhBG上的基底外侧NH 4+负载支持分泌方向的NH 4+转运。用~（86）Rb摄取法和哇巴因敏感电流法测定NKCC 1对NH_4 ~+的转运能力，结果表明NH_4 ~+在T84细胞中的转运能力与K ~+相当，而Na ~+-K ~+-ATPase对NH_4 ~+的转运能力与K ~+相当。T84细胞表达基底外侧NH 4+转运蛋白RhBG和顶端NH 4+转运蛋白RhCG的mRNA。在T84细胞中，由14 C-甲基铵（MA）的摄取和通量决定的NH 4+在分泌方向上的净运输表明功能性RhG蛋白活性。在结肠隐窝细胞模型中，NH 4+在分泌方向上的转运的发生可能用于使NH 4+的净吸收最小化，因为表面细胞NH 4+吸收。这些研究结果表明，我们重新思考目前对远端结肠NH 4+处理的有限理解，认为这仅仅是由于被动吸收。
Although colonic lumen NH4+levels are high, 15–44 mM normal range in humans, relatively few studies have addressed the transport mechanisms for NH4+. More extensive studies have elucidated the transport of NH4+in the kidney collecting duct, which involves a number of transporter processes also present in the distal colon. Similar to NH4+secretion in the renal collecting duct, we show that the distal colon secretory model, T84 cell line, has the capacity to secrete NH4+and maintain an apical-to-basolateral NH4+gradient. NH4+transport in the secretory direction was supported by basolateral NH4+loading on NKCC1, Na+-K+-ATPase, and the NH4+transporter, RhBG. NH4+was transported on NKCC1 in T84 cells nearly as well as K+as determined by bumetanide-sensitive86Rb-uptake.86Rb-uptake and ouabain-sensitive current measurement indicated that NH4+is transported by Na+-K+-ATPase in these cells to an equal extent as K+. T84 cells expressed mRNA for the basolateral NH4+transporter RhBG and the apical NH4+transporter RhCG. Net NH4+transport in the secretory direction determined by14C-methylammonium (MA) uptake and flux occurred in T84 cells suggesting functional RhG protein activity. The occurrence of NH4+transport in the secretory direction within a colonic crypt cell model likely serves to minimize net absorption of NH4+because of surface cell NH4+absorption. These findings suggest that we rethink the present limited understanding of NH4+handling by the distal colon as being due solely to passive absorption.