Kuwahara M, Sasaki S, Marumo F
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Am J Physiol. 1990 Dec;259(6 Pt 2):F902-9. doi: 10.1152/ajprenal.1990.259.6.F902.
To clarify mechanisms of intracellular pH (pHi) regulation in outer stripe of outer medullary collecting duct (OMCDOS), isolated perfused OMCDOS of the rabbit were loaded with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), and single cell pHi was monitored by an image processing system. Initial pHi recovery rates (dpHi/dt, pH unit/s x 10(3)) after intracellular acid load made by NH4Cl prepulse were determined. In the absence of exogenous CO2-HCO3-, dpHi/dt was 12.3 +/- 0.9 (means +/- SE) in principal cells (PC), and 11.5 +/- 1.0 in intercalated cells (IC). In PC, total ambient Na+ removal halted pHi recovery (dpHi/dt = 0.6 +/- 0.5), and pHi recovered when Na+ was added to the basolateral (dpHi/dt = 14.7 +/- 0.8) but not to the luminal (dpHi/dt = 0.9 +/- 0.5) solutions. This bath Na+ effect was amiloride inhibitable. In IC, pHi recovered (dpHi/dt = 6.4 +/- 0.3) in the absence of ambient Na+. This pHi recovery was significantly reduced by luminal 0.5 mM N-ethylmaleimide (NEM) or 0.5 mM N,N'-dicyclohexylcarbodiimide (DCCD). Basolateral NEM or DCCD had no significant effect. Basolateral addition of Na+ significantly accelerated the pHi recovery. These data suggest the presence of basolateral Na(+)-H+ exchange in both PC and IC, and luminal NEM- and DCCD-sensitive H+ pump in IC of rabbit OMCDOS.
为阐明外髓集合管外带（OMCDOS）细胞内pH（pHi）调节机制，将兔分离灌注的OMCDOS用2'，7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）负载，并用图像处理系统监测单细胞pHi。测定氯化铵预脉冲引起细胞内酸负荷后初始pHi恢复率（dpHi/dt，pH单位/秒×10³）。在无外源性CO₂-HCO₃⁻时，主细胞（PC）的dpHi/dt为12.3±0.9（均值±标准误），闰细胞（IC）为11.5±1.0。在PC中，完全去除细胞外液中的Na⁺会使pHi恢复停止（dpHi/dt = 0.6±0.5），当在基底外侧加入Na⁺时pHi恢复（dpHi/dt = 14.7±0.8），但在管腔侧加入Na⁺时则不然（dpHi/dt = 0.9±0.5）。这种浴液中Na⁺的作用可被氨氯吡咪抑制。在IC中，在无细胞外液Na⁺时pHi恢复（dpHi/dt = 6.4±0.3）。管腔侧加入0.5 mM N-乙基马来酰亚胺（NEM）或0.5 mM N，N'-二环己基碳二亚胺（DCCD）可显著降低这种pHi恢复。基底外侧加入NEM或DCCD无显著影响。基底外侧加入Na⁺可显著加速pHi恢复。这些数据表明兔OMCDOS的PC和IC中均存在基底外侧Na⁺-H⁺交换，且IC中存在管腔侧对NEM和DCCD敏感的H⁺泵。
