Na+-dependent HCO3- uptake into the rat choroid plexus epithelium is partially DIDS sensitive
Na+-dependent HCO3- uptake into the rat choroid plexus epithelium is partially DIDS sensitive
复制标题
DOI：
10.1152/ajpcell.00313.2005
复制
发表时间：
2005-12-01
影响因子：
5.5
通讯作者：
Aalkjaer, C
中科院分区：
文献类型：
--
作者：
Bouzinova, EV;Praetorius, J;Aalkjaer, C
一些研究表明，Na+和HCO 3-运输参与脑脊液的形成。最近，两种Na+依赖性HCO 3转运蛋白定位于大鼠脉络丛的上皮细胞（NBCn 1和NCBE），并且还检测到第三种蛋白质（NBCe 2）的mRNA（Praetorius J，Nejsum LN和Nielsen S. Am J Physiol Cell Physiol 286：C601 - C610，2004）。我们的目标是通过免疫组织化学和免疫金电子显微镜将NBCe 2免疫定位到脉络丛，并通过使用双激发波长pH敏感染料（BCECF）测量细胞内pH（pHi）来功能性地表征分离的大鼠脉络丛中碳酸氢盐转运。来自COOH-末端和NH 2-末端NBCe 2肽的抗血清均将NBCe 2定位于脉络丛上皮细胞的刷状缘膜结构域。向浴液中添加CO2/HCO 3-后，脉络膜细胞的稳态pHi从7.03 +/-0.02增加到7.38 +/- 0.02（n = 41）。这种增加是Na+依赖性和抑制的Cl-和HCO 3-转运抑制剂DIDS（200 μ M）。这表明存在Na+依赖性、部分DIDS敏感性HCO 3摄取。酸加载后的pHi恢复显示初始Na+和HCO 3依赖性净碱通量为0.828 +/- 0.116 mM/s（n = 8）。在CO2/HCO 3-存在下的初始通量不受DIDS的影响。我们的数据支持大鼠脉络丛上皮细胞存在对DIDS敏感和不敏感的Na+和HCO 3依赖性碱基装载剂摄取。这与该组织中三种碱基转运蛋白NBCn 1、Na+驱动的Cl-碳酸氢盐交换剂和NBCe 2的定位一致。
Several studies suggest the involvement of Na+ and HCO3- transport in the formation of cerebrospinal fluid. Two Na+-dependent HCO3- transporters were recently localized to the epithelial cells of the rat choroid plexus (NBCn1 and NCBE), and the mRNA for a third protein was also detected (NBCe2) (Praetorius J, Nejsum LN, and Nielsen S. Am J Physiol Cell Physiol 286: C601 - C610, 2004). Our goal was to immunolocalize the NBCe2 to the choroid plexus by immunohistochemistry and immunogold electronmicroscopy and to functionally characterize the bicarbonate transport in the isolated rat choroid plexus by measurements of intracellular pH (pHi) using a dual-excitation wavelength pH-sensitive dye (BCECF). Both antisera derived from COOH-terminal and NH2-terminal NBCe2 peptides localized NBCe2 to the brush-border membrane domain of choroid plexus epithelial cells. Steady-state pHi in choroidal cells increased from 7.03 +/- 0.02 to 7.38 +/- 0.02 (n = 41) after addition of CO2/HCO3- into the bath solution. This increase was Na+ dependent and inhibited by the Cl- and HCO3- transport inhibitor DIDS (200 mu M). This suggests the presence of Na+-dependent, partially DIDS-sensitive HCO3- uptake. The pHi recovery after acid loading revealed an initial Na+ and HCO3- dependent net base flux of 0.828 +/- 0.116 mM/s (n = 8). The initial flux in the presence of CO2/HCO3- was unaffected by DIDS. Our data support the existence of both DIDS-sensitive and - insensitive Na+- and HCO3- dependent base loader uptake into the rat choroid plexus epithelial cells. This is consistent with the localization of the three base transporters NBCn1, Na+-driven Cl- bicarbonate exchanger, and NBCe2 in this tissue.