Weissberg P L, Little P J, Cragoe E J, Bobik A
Am J Physiol. 1987 Aug;253(2 Pt 1):C193-8. doi: 10.1152/ajpcell.1987.253.2.C193.
We have investigated the role of the Na-H antiport in the regulation of intracellular pH (pHi) in vascular smooth muscle. Experiments were conducted on contractile-state rat aortic smooth muscle cells grown in primary culture and loaded with the pH-sensitive, fluorescent indicator 2',7',-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF). Cells equilibrated in a normal physiological salt solution (PSS) containing 135 mM Na, pH 7.4 at 37 degrees C, had a pHi of 7.16 +/- 0.04 (means +/- SE; n = 8). 5-(N-ethyl-N-isopropyl)amiloride (EIPA) caused a concentration-dependent fall in pHi. Removal of extracellular Na caused an intracellular acidification that was rapidly reversed on replacement of Na. The rate of recovery from NH4Cl-induced intracellular acidosis was dependent on extracellular Na concentration (Km 14.6 +/- 2.8 mM) and was accelerated by increasing the transmembrane Na gradient and slowed by decreasing it. Recovery from acidosis was completely abolished by either EIPA or the absence of extracellular Na. These results demonstrate that the Na-H antiport is an important mechanism for the maintenance and regulation of pHi in vascular smooth muscle cells. The BCECF fluorescence technique provides an ideal method for further studies on the mechanisms for pHi regulation in these cells.
我们研究了钠氢逆向转运体在调节血管平滑肌细胞内pH值（pHi）中的作用。实验在原代培养的收缩状态大鼠主动脉平滑肌细胞上进行，这些细胞加载了对pH敏感的荧光指示剂2',7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）。细胞在含有135 mM钠、pH 7.4的正常生理盐溶液（PSS）中于37℃平衡时，其pHi为7.16±0.04（平均值±标准误；n = 8）。5-（N-乙基-N-异丙基）氨氯吡脒（EIPA）导致pHi呈浓度依赖性下降。去除细胞外钠会引起细胞内酸化，在重新加入钠后迅速逆转。从氯化铵诱导的细胞内酸中毒中恢复的速率取决于细胞外钠浓度（Km为14.6±2.8 mM），通过增加跨膜钠梯度可加速恢复，而降低跨膜钠梯度则会减慢恢复速度。EIPA或缺乏细胞外钠均可完全消除酸中毒的恢复。这些结果表明，钠氢逆向转运体是维持和调节血管平滑肌细胞pHi的重要机制。BCECF荧光技术为进一步研究这些细胞中pHi调节机制提供了理想的方法。
