Axial heterogeneity of sodium-bicarbonate cotransporter expression in the rabbit proximal tubule
Axial heterogeneity of sodium-bicarbonate cotransporter expression in the rabbit proximal tubule
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DOI：
10.1152/ajprenal.1998.274.3.f628
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发表时间：
1998-03-01
影响因子：
4.2
通讯作者：
Kurtz, I
中科院分区：
文献类型：
--
作者：
Abuladze, N;Lee, I;Kurtz, I
一般认为Na（HCO 3）（n）共转运是介导早期近端小管基底外侧碳酸氢盐流出的最重要机制。在晚期近端小管（S-3段）和延髓S-1和S-2段中存在基底外侧Na（HCO 3）（n）共转运一直存在争议。肾钠-碳酸氢盐协同转运蛋白（NBC）最近已从大鼠（M。F.罗梅罗，M。A. Hediger，E. L. Boulpaep和W. F.硼J. Am.秒Nephrol. 7：1259，1996）、蝾螈（M. F.罗梅罗湾A. Hediger，E. L. Boulpaep和W. F.硼Nature 387：409-413，1997）和人（C. E. Burnham，H. Amlal，Z. Wang，G. E. Shull和M.索莱马尼272：19111-19114，1997）。NBC在肾脏中的定位尚不清楚。本研究旨在定位兔近端小管中NBC mRNA的表达。原位杂交研究与功能研究相结合的Na（HCO 3）（n）共转运在浅和延髓S-1，S-2和S-3段的兔近端小管。结果表明，NBC mRNA主要定位于皮质，在外髓质中表达较少。内髓未见NBC表达。在S-1近曲小管中，NBC mRNA表达水平最高。NBC在S-3节段中以低水平表达，在S-2节段中以中等水平表达。在碳酸氢盐缓冲溶液中，Na（HCO 3）（n）共转运介导的碱流出率在浅表和近端小管节段中遵循相似的模式，即，S-1 > S-2 > S-3髓质S-1段基底外侧Na（HCO_3）（n）共转运率最高，近端小管中NBC表达水平最高。
It is generally accepted that Na(HCO3)(n) cotransport is the most important mechanism mediating basolateral bicarbonate efflux in the early proximal tubule. The presence of basolateral Na(HCO3)(n) cotransport in the late proximal tubule (S-3 segment) and in the juxtamedullary S-1 and S-2 segments has been controversial. The renal sodium-bicarbonate cotransporter (NBC) has been recently cloned from rat (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. J. Am. Sec. Nephrol. 7: 1259, 1996), salamander (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. Nature 387: 409-413, 1997), and human (C. E. Burnham, H. Amlal, Z. Wang, G. E. Shull, and M. Soleimani. J. Biol. Chem. 272: 19111-19114, 1997). The localization of NBC in the kidney is unknown. The present study was designed to localize NBC mRNA expression in the rabbit proximal tubule. In situ hybridization studies were combined with functional studies of basolateral Na(HCO3)(n) cotransport in superficial and juxtamedullary S-1, S-2, and S-3 segments of the rabbit proximal tubule. The results demonstrate that NBC mRNA is localized predominantly to the cortex, with less expression in the outer medulla. NBC expression was not detected in the inner medulla. The highest level of NBC mRNA is in the S-1 proximal tubule. NBC is expressed at a low levels in the S-3 segment, with intermediate expression in the S-2 segment. In bicarbonate-buffered solutions, the rate of base efflux mediated by Na(HCO3)(n) cotransport followed a similar pattern in superficial and juxtamedullary proximal tubule segments, i.e., S-1 > S-2 > S-3 The juxtamedullary S-1 segment had the greatest rate of basolateral Na(HCO3)(n) cotransport and the highest level of NBC expression in the proximal tubule.