ION-TRANSPORT PROPERTIES OF CULTURED BOVINE PANCREATIC DUCT EPITHELIAL-CELLS

Primary cultures of bovine pancreatic duct epithelial cells grown on p ermeable supports exhibit electrogenic transepithelial ion transport. The short-circuit current (I-sc) generated by unstimulated duct cell m onolayers and the increase in I-sc elicited by increased levels of cyc lic adenosine monophosphate (cAMP) were greater in monolayers bathed b y bicarbonate-containing solution compared with monolayers bathed by n ominally bicarbonate-free solution. An inhibitor of epithelial sodium channels (amiloride, 10 mu M) had no effect on I-sc, whereas a Cl- cha nnel blocker, N-phenylanthranilic acid (DPC: 1 mM), reduced the forsko lin-stimulated I-sc by similar to 50% in the absence or presence of bi carbonate. Bumetanide tan inhibitor of Na+,K+,2Cl(-) cotransport activ ity; 10 mu M) reduced forskolin-stimulated I-sc by 49 +/- 6% in bicarb onate-free bathing solution land by only 18 +/- 1% in bicarbonate-cont aining solution. Measurements of unidirectional Cl-36(-) flux across s hort-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 exp osure 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 simila r to 1.5-fold greater than the permeability coefficient measured in th e absorptive direction, indicating net secretion. These results sugges t that primary cultures of bovine pancreatic duct epithelial cells sec rete both Cl- and HCO3-.