Intracellular pH regulation in trout urinary bladder epithelium: Na(+)-H+(NH4+) exchange.
Intracellular pH regulation in trout urinary bladder epithelium: Na(+)-H+(NH4+) exchange.
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鳟鱼膀胱上皮细胞内 pH 调节：Na( )-H (NH4 ) 交换。
DOI：
10.1152/ajpregu.1991.261.3.r652
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发表时间：
1991
影响因子：
--
通讯作者：
S. Bryson
中科院分区：
文献类型：
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作者：
W. Marshall;S. Bryson
我们使用显微荧光法和胞质捕获的pH敏感荧光团2',7'-双（2-羧基乙基）-5(6)-羧基荧光素（BCECF）原位测量膀胱上皮单个上皮细胞的细胞内pH （pHi）。在pH为7.8的沐浴液中，静息pHi值为7.21 +/- 0.03 （n = 40个膀胱，489个细胞），表明H+不是被动分布在质膜上，而是根据其电化学梯度被挤出。虽然暴露于高碳酸血症（5% CO2饱和度）可可逆地降低pHi，但粘膜添加20 mM NH4+可可逆地增加pHi。NH4+效应恢复缓慢，且缺乏酸负荷pHi过低；这被解释为表明显著的NH4+渗透性。粘膜添加的阿米洛利阻断了高碳酸中毒的恢复，表明顶端Na(+)-H+交换参与了pHi调节。当粘膜侧浸泡在模拟尿液中（2 mM NaCl）时，向基底外侧添加0.5 mM NH4+可显著增加粘膜到浆膜的单向Na+通量，而这种增加被粘膜添加的氨酰胺阻断。我们得出结论，位于顶部的Na(+)-H+交换在pHi调节中很重要，并且可能接受NH4+作为Na+的对偶。
We measured intracellular pH (pHi) of single epithelial cells in situ in the urinary bladder epithelium using microspectrofluorometry and the cytoplasmically trapped pH-sensitive fluorophore, 2',7'-bis(2-carboxyethyl)-5(6)- carboxyfluorescein (BCECF). The resting pHi was 7.21 +/- 0.03 (n = 40 bladders, 489 cells) in pH 7.8 bathing solutions, indicating that H+ is not passively distributed across the plasma membrane and is extruded against its electrochemical gradient. Whereas exposure to hypercapnia (5% CO2 saturation) reversibly decreased pHi, mucosally added 20 mM NH4+ reversibly increased pHi. Recovery from the NH4+ effect was slow and lacked an acid-load pHi undershoot; this is interpreted as suggesting significant NH4+ permeability. Recovery from hypercapnic acidosis was blocked by mucosally added amiloride, indicating that apical Na(+)-H+ exchange is involved in pHi regulation. Addition of 0.5 mM NH4+ to the basolateral side when the mucosal side was bathed in mock urine (2 mM NaCl) significantly increased undirectional mucosal-to-serosal Na+ flux, and the increase was blocked by mucosally added amiloride. We conclude that an apically located Na(+)-H+ exchange is important in pHi regulation and may also accept NH4+ as the counterion for Na+.