CFTR activation raises extracellular pH of NIH/3T3 mouse fibroblasts and C127 epithelial cells.
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.
Luckie
D B
DB
Department of Physiology and Lyman Briggs School, Michigan State University, East Lansing 48824-1101, USA.
Singh
C N
CN
Wine
J J
JJ
Wilterding
J H
JH
D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
C505032:CFTR protein, human; D011994:Recombinant Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin