CFTR-INDEPENDENT ATP RELEASE FROM EPITHELIAL-CELLS TRIGGERED BY MECHANICAL STIMULI

Cystic fibrosis transmembrane conductance regulator (CFTR)-mediated AT P efflux has been proposed as an autocrine mechanism for regulating ch loride secretion through other types of chloride channels. Although we found in previous studies that wild-type CFTR channels bathed with hi gh-ATP solutions do not conduct ATP at rates that can be measured with the patch-clamp technique, those experiments would not have detected very small or electroneutral ATP fluxes through CFTR or ATP efflux thr ough other pathways that might be regulated by CFTR. To examine these possibilities, we have now used a sensitive luciferase luminometric as say to measure ATP efflux from epithelial and nonepithelial cell lines . Adenosine 3',5'-cyclic monophosphate (cAMP) stimulation did not rais e external ATP concentration above the background noise in any of the cell lines tested [T84, Calu-3, SHTEo(-) and Sigma CFTE29o(-) (colonic and airway human epithelial cells, respectively), NIH/3T3 fibroblasts , and Chinese hamster ovary cells], and variations in ATP release were not correlated with CFTR expression. The rate of ATP release was unaf fected by cAMP but was exquisitely sensitive to mechanical perturbatio ns in both CFTR expressing and nonexpressing cells. Mechanically induc ed, CFTR-independent ATP release may be a physiologically relevant mec hanism of epithelial regulation, which has not previously been fully a ppreciated.