Osmotic activation of Na(+)-H+ exchange in human endothelial cells.
Osmotic activation of Na(+)-H+ exchange in human endothelial cells.
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人内皮细胞中 Na()-H 交换的渗透激活。
DOI：
10.1152/ajpcell.1990.259.4.c640
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Brock,TA
中科院分区：
文献类型：
--
作者：
Escobales,N;Longo,E;CragoeJr,EJ;Danthuluri,NR;Brock,TA
在培养的人脐静脉内皮细胞（HEC）中，用pH敏感的荧光染料2 '，7'-双（羧乙基）-5，6-羧基荧光素（22 Na内流）研究了Na（+）-H+交换依赖机制对细胞内pH（pHi）的调节。在不含碳酸氢盐的Na+培养基中孵育的HEC的基础pHi为6.99 +/- 0.03。在用尼日利亚菌素或NH 4Cl预脉冲进行酸负载的HEC中，pHi恢复通过Na（+）依赖性机制发生，该机制被5-（N-乙基-N-异丙基）阿米洛利（EIPA）抑制。阿米洛利衍生物抑制22 Na流入的效力为EIPA大于5-（N，N-二甲基）阿米洛利大于阿米洛利[Ki（细胞外Na = 30 mM）分别= 17 nM、150 nM和8.8 μ M]。在酸负载的HEC中，EIPA敏感的22 Na内流是外部Na+浓度（0-130 mM）的饱和函数，表现出的Km和Vmax分别约为19.70 +/- 0.14 mM和34.01 +/- 2.2 nmol.10（6）cells-1.min-1。H+外流也依赖于外部Na+和EIPA阻断。在静息pHi时，HEC Na（+）-H+交换轻微刺激介质渗透压摩尔浓度的增加。当HEC在高渗（蔗糖）介质中酸负荷时，Na（+）-H+交换活性（~（22）Na内流或pHi恢复）显著增加。总的来说，这些数据表明，培养的HEC中的pHi可以通过Na（+）-H+交换剂调节，并且其活性可以在酸性pHi下受到渗透压摩尔浓度的显著影响。
Regulation of intracellular pH (pHi) via a Na(+)-H+ exchange-dependent mechanism was studied in cultured human umbilical vein endothelial cells (HEC) using the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein, as well as measuring 22Na influx. Basal pHi of HEC incubated in a bicarbonate-free Na+ medium was 6.99 +/- 0.03. In HEC that had been acid-loaded using nigericin or a NH4Cl prepulse, pHi recovery occurred via a Na(+)-dependent mechanism that was inhibited by 5-(N-ethyl-N-isopropyl)amiloride (EIPA). The potency of amiloride derivatives to inhibit 22Na influx was EIPA greater than 5-(N,N-dimethyl)amiloride greater than amiloride [Ki (extracellular Na = 30 mM) = 17 nM, 150 nM, and 8.8 microM, respectively]. EIPA-sensitive 22Na influx in acid-loaded HEC was a saturable function of the external Na+ concentration (0-130 mM), exhibiting an approximate Km and Vmax of 19.70 +/- 0.14 mM and 34.01 +/- 2.2 nmol.10(6) cells-1.min-1, respectively. H+ efflux was also dependent on external Na+ and blocked by EIPA. At resting pHi, HEC Na(+)-H+ exchange was slightly stimulated by increases in medium osmolality. However, when HEC were acid-loaded in the presence of hypertonic (sucrose) medium, Na(+)-H+ exchange activity (22Na influx or pHi recovery) increased markedly. Overall, these data indicate that pHi in cultured HEC can be regulated by a Na(+)-H+ exchanger and that its activity can be markedly influenced by osmolality at acidic pHi.