Wagner C A, Giebisch G, Lang F, Geibel J P
Institute of Physiology I, University of Tübingen, Gmelinstrasse 5, 72076 Tübingen, Germany.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9665-8. doi: 10.1073/pnas.95.16.9665.
Two mechanisms of H+ ion secretion in the proximal tubule that mediate bicarbonate reabsorption have been identified: the brush border Na/H exchanger and electrogenic H+ ion secretion. Angiotensin II (AII) has been shown to be a regulator of the luminal Na+/H+ exchanger and the basolateral Na+/HCO3- cotransporter. In the present study, we examined the effects of AII on H+-ATPase activity in isolated proximal tubule fragments. H+-ATPase activity was assessed by monitoring intracellular pH after Na+ removal from the bath. In addition, we investigated the effects on pH recovery of the proton pump inhibitor bafilomycin A1, removal of Cl-, and of colchicine. pH was continuously measured with the pH-sensitive fluorescent dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Recovery of cell pH was observed in the absence of external Na+ and was significantly accelerated by AII. The AII-stimulated pH recovery was completely abolished by bafilomycin A1, by removal of Cl-, by NPPB [5-nitro-2-(3-phenylpropylamino)-benzoate; a potent Cl- channel blocker], and by colchicine. We conclude from these studies that AII stimulates proton extrusion via H+-ATPase by a Cl--dependent process involving brush border insertion of vesicles. This process may contribute to up-regulation of HCO3- reabsorption along the proximal tubule when tubules are exposed to AII.
刷状缘钠/氢交换器和电生性氢离子分泌。血管紧张素II（AII）已被证明是管腔钠/氢交换器和基底外侧钠/碳酸氢根共转运体的调节剂。在本研究中，我们检测了AII对分离的近端小管片段中氢离子ATP酶活性的影响。通过监测浴液中钠去除后细胞内pH值来评估氢离子ATP酶活性。此外，我们研究了质子泵抑制剂巴弗洛霉素A1、氯离子去除和秋水仙碱对pH值恢复的影响。使用pH敏感荧光染料2',7'-双（2-羧乙基）-5（6）-羧基荧光素（BCECF）连续测量pH值。在无细胞外钠的情况下观察到细胞pH值的恢复，且AII可显著加速该恢复过程。AII刺激的pH值恢复被巴弗洛霉素A1、氯离子去除、5-硝基-2-（3-苯丙基氨基）-苯甲酸酯（NPPB；一种有效的氯离子通道阻滞剂）和秋水仙碱完全消除。我们从这些研究中得出结论，AII通过涉及囊泡刷状缘插入的氯离子依赖性过程刺激氢离子通过氢离子ATP酶排出。当肾小管暴露于AII时，该过程可能有助于近端小管碳酸氢盐重吸收的上调。
