Stimulation of HCO3- secretion across cystic fibrosis pancreatic duct cells by extracellular ATP.

Previous studies have demonstrated that extracellular ATP is able to activate Ca2+-dependent Cl- channels which may be important in circumventing the defective cAMP-dependent pancreatic ductal HCO3- secretion in cystic fibrosis (CF). The present study further investigated the effect of extracellular ATP on the stimulation of HCO3- secretion across CF pancreatic duct cells (CFPAC-1). Cells were grown in culture plate inserts which enabled the access of a pH microelectrode to the apical compartment. Changes in apical pH upon stimulation by extracellular ATP, as an indication of HCO3- secretion, were measured. ATP induced a rapid increase in apical pH, which reached a plateau with an averaged pH unit of 0.3 higher than that measured in unstimulated cells. The effect of ATP was concentration dependent. The ATP-induced change in pH could be blocked by apical addition of Cl- channel blockers, indicating that activation of apical Cl- channel is vital for HCO3- secretion by the pancreatic duct cells. Together with the previous finding, the present study suggests that HCO3- secretion may be stimulated in CF pancreatic duct cells by extracellular ATP via a cAMP-independent pathway.