Ion-transport properties of cultured bovine pancreatic duct epithelial cells

Primary cultures of bovine pancreatic duct epithelial cells grown on permeable supports exhibit electrogenic transepithelial ion transport. The short-circuit current (I-sc) generated by unstimulated duct cell monolayers and the increase in I-sc elicited by increased levels of cyclic adenosine monophosphate (cAMP) were greater in monolayers bathed by bicarbonate-containing solution compared with monolayers bathed by nominally bicarbonate-free solution. An inhibitor of epithelial sodium channels (amiloride, 10 mu M) had no effect on I-sc, whereas a Cl- channel blocker, N-phenylanthranilic acid (DPC: 1 mM), reduced the forskolin-stimulated I-sc by similar to 50% in the absence or presence of bicarbonate. Bumetanide tan inhibitor of Na+,K+,2Cl(-) cotransport activity; 10 mu M) reduced forskolin-stimulated I-sc by 49 +/- 6% in bicarbonate-free bathing solution land by only 18 +/- 1% in bicarbonate-containing solution. Measurements of unidirectional Cl-36(-) flux across short-circuited ductal monolayers in a bicarbonate-containing solution revealed that net Cl- secretion accounted for the I-sc during secretin stimulation. However, the basal I-sc and the I-sc measured during exposure to secretin plus bumetanide were significantly greater than net Cl- flux. The permeability coefficient for [C-14]acetate (a surrogate tracer for bicarbonate) measured in the secretory direction was similar to 1.5-fold greater than the permeability coefficient measured in the absorptive direction, indicating net secretion. These results suggest that primary cultures of bovine pancreatic duct epithelial cells secrete both Cl- and HCO3-.