Purinergic agonists have been considered for the treatment of respiratory epithelia in
cystic fibrosis (CF) patients. The pancreas, one of the most seriously affected organs in CF, expresses various
purinergic receptors. Studies on the rodent pancreas show that purinergic signaling regulates pancreatic secretion. In the present study we aim to identify Cl(-) and K(+) channels in human pancreatic ducts and their regulation by
purinergic receptors. Human pancreatic duct epithelia formed by Capan-1 or CFPAC-1 cells were studied in open-circuit Ussing chambers. In Capan-1 cells,
ATP/
UTP effects were dependent on intracellular Ca(2+). Apically applied
ATP/
UTP stimulated CF transmembrane conductance regulator (CFTR) and Ca(2+)-activated Cl(-) (
CaCC) channels, which were inhibited by CFTRinh-172 and
niflumic acid, respectively. The basolaterally applied
ATP stimulated CFTR. In CFPAC-1 cells, which have mutated CFTR, basolateral
ATP and
UTP had negligible effects. In addition to Cl(-) transport in Capan-1 cells, the effects of
5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DC-EBIO) and
clotrimazole indicated functional expression of the intermediate conductance K(+) channels (IK, KCa3.1). The apical effects of
ATP/
UTP were greatly potentiated by the IK channel opener DC-EBIO. Determination of
RNA and
protein levels revealed that Capan-1 cells have high expression of TMEM16A (ANO1), a likely
CaCC candidate. We conclude that in human pancreatic duct cells
ATP/
UTP regulates via
purinergic receptors both Cl(-) channels (TMEM16A/ANO1 and CFTR) and K(+) channels (IK). The K(+) channels provide the driving force for Cl(-)-channel-dependent secretion, and
luminal ATP provided locally or secreted from acini may potentiate secretory processes. Future strategies in augmenting pancreatic duct function should consider sidedness of purinergic signaling and the essential role of K(+) channels.