The stoichiometry of the electrogenic sodium bicarbonate cotransporter pNBC1 in mouse pancreatic duct cells is 2 HCO3-:1 Na+
The stoichiometry of the electrogenic sodium bicarbonate cotransporter pNBC1 in mouse pancreatic duct cells is 2 HCO3-:1 Na+
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DOI：
10.1111/j.1469-7793.2001.0375i.x
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发表时间：
2001-03-01
影响因子：
5.5
通讯作者：
Cotton, CU
中科院分区：
文献类型：
--
作者：
Gross, E;Abuladze, N;Cotton, CU
1.产电碳酸氢钠协同转运蛋白pNBC 1。据信通过将碳酸氢盐穿过基底外侧膜转运到细胞中，在胰管细胞分泌碳酸氢盐中起主要作用。热力学预测，只有当协同转运蛋白的反转电位与细胞膜电位呈负相关时，或者等效地HCO 3-：Na+化学计量不大于2：1时，才能实现此功能。然而，没有关于胰腺细胞中pNBC 1的逆转电位或HCO 3-：Na+化学计量的数据。我们研究了pNBC 1在小鼠胰管细胞中的功能。对总RNA的RT-PCR分析显示，这些细胞含有pNBC 1的信息，但不含有kNBC 1、NBC 2或NBC3.3的信息。为了测量协同转运蛋白活性，将小鼠胰管细胞在多孔基质上生长至汇合，安装在Ussing室中，并用阿替霉素B透化顶端质膜。通过pNBC 1的离子通量是通过在基底外侧质膜上施加Na+浓度梯度来实现的。通过共转运蛋白的电流被分离为由于可逆抑制剂二硝基二苯乙烯二磺酸盐（DNDS）引起的差电流。在三个不同的Na+浓度梯度下测得的协同转运蛋白的电流-电压关系在约100 mV的范围内呈线性。从这些电流-电压关系获得的反转电位数据均对应于2 HCO 3-：1 Na+化学计量。数据表明pNBC 1在小鼠胰管细胞中功能性表达。协同转运蛋白在这些细胞中以2 HCO 3-：1 Na+的化学计量比运作，并介导碳酸氢盐穿过基底外侧膜进入细胞的转运。
1. electrogenic sodium bicarbonate cotransporter pNBC1. is believed to play a major role in the secretion of bicarbonate by pancreatic duct cells, by transporting bicarbonate into the cell across the basolateral membrane. Thermodynamics predict that this function can be achieved only if the reversal potential of the cotransporter is negative to the cell's membrane potential, or equivalently that the HCO3-:Na+ stoichiometry is not larger then 2:1. However, there are no data available on either the reversal potential or the HCO3-:Na+ stoichiometry of pNBC1 in pancreatic cells.2. We studied pNBC1 function in mouse pancreatic duct cells. RT-PCR analysis of total RNA revealed that these cells contain the message for pNBC1, but not for kNBC1, NBC2 or NBC3.3. To measure cotransporter activity, mouse pancreatic duct cells were grown to confluence on a porous substrate, mounted in an Ussing chamber, and the apical plasma membrane permeabilized with amphotericin B. Ion flux through pNBC1 was achieved by applying Na+ concentration gradients across the basolateral plasma membrane. The current through the cotransporter was isolated as the difference current due to the reversible inhibitor dinitrostilbene disulfonate (DNDS).4. Current-voltage relationships for the cotransporter, measured at three different Na+ concentration gradients, were linear over a range of about 100 mV. The reversal potential data, obtained from these current-voltage relationships, all corresponded to a 2 HCO3-:1 Na+ stoichiometry.5. The data indicate that pNBC1 is functionally expressed in mouse pancreatic duct cells. The cotransporter operates with a 2 HCO3-:1 Na+ stoichiometry in these cells, and mediates the transport of bicarbonate into the cell across the basolateral membrane.