CFTR expression in C127 cells is associated with enhanced cell shrinkage and ATP extrusion in Cl--free medium

In this study we have employed three lines of C127 murine cells, C127 CFTRw/t, C127 CFTRΔF508 and C127 mock, transfected with, respectively, wild type, ΔF508 mutant human CFTR cDNA or the vector only. In the first 10 minutes of a Cl--free incubation the three cell lines exhibit a significant shrinkage due to a loss of K+ and Cl-. However, C127 CFTRw/t cells shrink more than C127 CFTRΔF508 and the mock cells. The supplementation of Cl--free medium with ATP causes a marked decrease in the cell volume of C127 CFTRΔF508 and of the mock cells but not of C127 CFTRw/t cells. ATP effect is mimicked by adenosine 5'-O-(3-thiotriphosphate), but neither by adenosine nor by UTP. Measurements of extracellular ATP indicate that during the Cl--free incubation C127 CFTRw/t cells extrude more ATP than the other two cell lines. The results are consistent with the hypothesis that CFTR enhances K+ and Cl- permeabilities by promoting the extrusion of ATP.