Luckie D B, Singh C N, Wine J J, Wilterding J H
Department of Physiology and Lyman Briggs School, Michigan State University, East Lansing 48824-1101, USA.
J Membr Biol. 2001 Feb 1;179(3):275-84. doi: 10.1007/s002320010052.
Cystic Fibrosis (CF) is caused by mutations in the gene for CFTR, a cAMP-activated anion channel found in apical membranes of wet epithelia. Since CFTR is permeable to HCO3- and changes in extracellular fluid composition may contribute to CF lung disease, we investigated possible differences in extracellular pH (pHo) between CFTR-expressing and control cell lines. The Cytosensor Microphysiometer was used to study forskolin-stimulated extracellular acidification rates in CFTR-expressing and control mouse mammary epithelial (C127) and fibroblast (NIH/3T3) cell lines. Forskolin, which activates CFTR via raised cAMP, caused decreased extracellular acidification of CFTR-expressing NIH/3T3 and C127 cells by 15-35%. By contrast, forskolin caused increased extracellular acidification of control cells by 10-20%. Ionomycin, which may activate CFTR via PKC, also elicited this decreased extracellular acidification signal only in cells expressing CFTR. In control experiments, dideoxyforskolin had no effect on the acidification rates and osmotic stimuli were shown to equally stimulate all cell lines. These results suggest a role for CFTR in controlling pHo and complement recent evidence that HCO3- dependent epithelial secretion may be reduced in amount and altered in composition in CF.
囊性纤维化（CF）是由CFTR基因的突变引起的，CFTR是一种在湿润上皮细胞顶膜中发现的cAMP激活的阴离子通道。由于CFTR对HCO3-具有通透性，且细胞外液成分的变化可能导致CF肺部疾病，我们研究了表达CFTR的细胞系与对照细胞系之间细胞外pH值（pHo）的可能差异。使用细胞传感器微生理仪研究了在表达CFTR的细胞系以及对照小鼠乳腺上皮（C127）和成纤维细胞（NIH/3T3）细胞系中，福斯高林刺激后的细胞外酸化速率。福斯高林通过提高cAMP来激活CFTR，导致表达CFTR的NIH/3T3和C127细胞的细胞外酸化降低了15%-35%。相比之下，福斯高林使对照细胞的细胞外酸化增加了10%-20%。离子霉素可通过蛋白激酶C激活CFTR，它也仅在表达CFTR的细胞中引发这种细胞外酸化信号的降低。在对照实验中，双脱氧福斯高林对酸化速率没有影响，并且渗透压刺激显示对所有细胞系的刺激作用相同。这些结果表明CFTR在控制pHo方面发挥作用，并且补充了最近的证据，即CF中依赖HCO3-的上皮分泌量可能减少且成分可能改变。
