Shrinkage-induced activation of Na+/H+ exchange in rat renal mesangial cells.
Shrinkage-induced activation of Na+/H+ exchange in rat renal mesangial cells.
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大鼠肾系膜细胞收缩诱导的 Na /H 交换激活。
DOI：
10.1152/ajpcell.1999.276.3.c674
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Boron,WF
中科院分区：
文献类型：
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作者：
Bevensee,MO;Bashi,E;Schlue,WR;Boyarsky,G;Boron,WF
用pH敏感染料2′，7 ′-双（2-羧乙基）-5（6）-羧基荧光素（BCECF）检测了高渗溶液对大鼠肾小球系膜细胞（单个细胞或群体）内pH（pHi）调节的影响。如果调节细胞外K+浓度（[K+]）以匹配预测的细胞内[K +]，BCECF的校准在收缩和未收缩的系膜细胞中是相同的。当pH值在6.7 ~ 7.4之间时，收缩细胞的固有缓冲能力（600 mosmol/kgH 2 O）是未收缩细胞的3倍（300 mosmol/kgH 2 O）。在名义上不存在CO2/的情况下，将细胞群暴露于补充有1000 mM甘露醇（600 mosmol/kgH 2 O）的HEPES缓冲液中，导致稳态pH值增加100.4。pH升高是由于Na+/H+交换的激活，因为在单细胞中，在不存在外部Na+或存在50 μM乙基异丙基氨氯吡咪（EIPA）的情况下，它被阻断。将细胞在无Cl−溶液中预孵育至少14 min可抑制收缩诱导的pH升高80%。我们计算了在正常和高渗条件下细胞群体中Na+/H+交换速率的pH依赖性，方法是将1）总酸排出速率的pH依赖性和2）EIPA不敏感的酸负载速率的pH依赖性相加。收缩碱使Na+/H+交换的pH依赖性移动了约0.7个pH单位。
Using the pH-sensitive dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), we examined the effect of hyperosmolar solutions, which presumably caused cell shrinkage, on intracellular pH (pHi) regulation in mesangial cells (single cells or populations) cultured from the rat kidney. The calibration of BCECF is identical in shrunken and unshrunken mesangial cells if the extracellular K+concentration ([K+]) is adjusted to match the predicted intracellular [K+]. For pHivalues between ∼6.7 and ∼7.4, the intrinsic buffering power in shrunken cells (600 mosmol/kgH2O) is threefold larger than in unshrunken cells (∼300 mosmol/kgH2O). In the nominal absence of CO2/, exposing cell populations to a HEPES-buffered solution supplemented with ∼300 mM mannitol (600 mosmol/kgH2O) causes steady-state pHito increase by ∼0.4. The pHiincrease is due to activation of Na+/H+exchange because, in single cells, it is blocked in the absence of external Na+or in the presence of 50 μM ethylisopropylamiloride (EIPA). Preincubating cells in a Cl−-free solution for at least 14 min inhibits the shrinkage-induced pHiincrease by 80%. We calculated the pHidependence of the Na+/H+exchange rate in cell populations under normosmolar and hyperosmolar conditions by summing1) the pHidependence of the total acid-extrusion rate and2) the pHidependence of the EIPA-insensitive acid-loading rate. Shrinkage alkali shifts the pHidependence of Na+/H+exchange by ∼0.7 pH units.