Kuwahara M, Sasaki S, Marumo F
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Am J Physiol. 1991 May;260(5 Pt 2):F635-42. doi: 10.1152/ajprenal.1991.260.5.F635.
The mechanisms of basolateral HCO3- (or related base) transport were examined in the outer stripe of the outer medullary collecting duct (OMCDo). Rabbit OMCDo were perfused in vitro and cell pH (pHi) of principal cells (PC) and intercalated cells (IC) was monitored with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) using fluorescence ratio imaging microscopy. Basolateral HCO3- exit was stimulated either by bath HCO3- reduction or by NH3/NH4(+)-induced cell alkalinization. Rates of pHi decrease were twice as high in IC than in PC. In both cell types HCO3- exit was dependent on Cl(-)-coupled and Na(+)-coupled mechanisms; the former was dominant in IC, whereas the latter was dominant in PC. pHi of PC and IC significantly increased by bath Cl- removal in the absence of Na+ and decreased by bath Na+ removal in the absence of Cl- but with amiloride. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) inhibited these pHi responses to a reduction of bath HCO3-, Cl-, or Na+, and an alkali loading. Our results suggest that 1) the capacity for basolateral HCO3- transport is twice as high in IC than in PC, 2) both PC and IC possess basolateral Na(+)-independent Cl(-)-HCO3- exchange and Na(+)-HCO3- cotransport, and 3) basolateral HCO3- transport is mediated mainly by Na(+)-HCO3- cotransport in PC and by Na(+)-independent Cl(-)-HCO3- exchange in IC.
我们对外髓集合管外带（OMCDo）基底外侧HCO₃⁻（或相关碱基）转运机制进行了研究。采用荧光比率成像显微镜，利用2',7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）监测体外灌注的兔OMCDo中主细胞（PC）和闰细胞（IC）的细胞内pH（pHi）。通过降低浴液中的HCO₃⁻或通过NH₃/NH₄⁺诱导的细胞碱化来刺激基底外侧HCO₃⁻流出。IC中pHi降低的速率是PC中的两倍。在两种细胞类型中，HCO₃⁻流出均依赖于Cl⁻偶联和Na⁺偶联机制；前者在IC中占主导，而后者在PC中占主导。在无Na⁺的情况下去除浴液中的Cl⁻，PC和IC的pHi显著升高；在无Cl⁻但有氨氯吡咪的情况下去除浴液中的Na⁺，pHi降低。4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS）抑制了这些对浴液中HCO₃⁻、Cl⁻或Na⁺减少以及碱负荷的pHi反应。我们的结果表明：1）IC中基底外侧HCO₃⁻转运能力是PC中的两倍；2）PC和IC均具有基底外侧不依赖Na⁺的Cl⁻-HCO₃⁻交换和Na⁺-HCO₃⁻共转运；3）基底外侧HCO₃⁻转运在PC中主要由Na⁺-HCO₃⁻共转运介导，在IC中由不依赖Na⁺的Cl⁻-HCO₃⁻交换介导。
