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Concurrent and Independent HCO 3 and Cl Secretion in a Human Pancreatic Duct Cell Line (CAPAN-1)

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Abstract.

The present study investigated both HCO 3 and Cl secretions in a human pancreatic duct cell line, CAPAN-1, using the short-circuit current (I sc ) technique. In Cl/HCO 3-containing solution, secretin (1 μm) or forskolin (10 μm) stimulated a biphasic rise in the I sc which initially reached a peak level at about 3 min and then decayed to a plateau level after 7 min. Removal of external Cl abolished the initial transient phase in the forskolin-induced I sc while the plateau remained. In HCO 3/CO2-free solution, on the contrary, only the initial transient increase in I sc was prominent. Summation of the current magnitudes observed in Cl-free and HCO 3-free solutions over a time course of 10 min gave rise to a curve which was similar, both in magnitude and kinetics, to the current observed in Cl/HCO 3-containing solution. Removal of external Na+ greatly reduced the initial transient rise in the forskolin-induced I sc response, and the plateau level observed under this condition was similar to that obtained in Cl-free solution, suggesting that Cl-dependent I sc was also Na+-dependent. Bumetanide (50 μm), an inhibitor of the Na+-K+-2Cl cotransporter, and Ba2+ (1 mm), a K+ channel blocker, could reduce the forskolin-induced I sc obtained in Cl/HCO 3-containing or HCO 3-free solution. However, they were found to be ineffective when external Cl was removed, indicating the involvement of these mechanisms in Cl secretion. On the contrary, the HCO 3-dependent (in the absence of external Cl) forskolin-induced I sc could be significantly reduced by carbonic anhydrase inhibitor, acetazolamide (45 μm). Basolateral application of amiloride (100 μm) inhibited the I sc ; however, a specific Na+-H+ exchanger blocker, 5-N-methyl-N-isobutylamiloride (MIA, 5–10 μm) was found to be ineffective, excluding the involvement of the Na+-H+ exchanger. However, an inhibitor of H+-ATPase, N-ethylmaleimide did suppress the I sc (IC50= 22 μm). Immunohistochemical studies also confirmed the presence of a vacuolar type of H+-ATPase in these cells. H2DIDS (100 μm), an inhibitor of Na+-HCO 3 cotransporter, was without effect. Apical addition of Cl channel blocker, diphenylamine-2,2′-dicarboxylic acid (DPC, 1 mm), but not disulfonic acids, DIDS (100 μm) or SITS (100 μm), exerted an inhibitory effect on both Cl and HCO 3-dependent forskolin-induced I sc responses. Histochemical studies showed discrete stainings of carbonic anhydrase in the monolayer of CAPAN-1 cells, suggesting that HCO 3 secretion may be specialized to a certain population of cells. The present results suggest that both HCO 3 and Cl secretion by the human pancreatic duct cells may occur concurrently and independently.

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Received: 17 October 1997/Revised: 3 April 1998

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Cheng, H., Leung, P., Cheng Chew, S. et al. Concurrent and Independent HCO 3 and Cl Secretion in a Human Pancreatic Duct Cell Line (CAPAN-1). J. Membrane Biol. 164, 155–167 (1998). https://doi.org/10.1007/s002329900401

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  • DOI: https://doi.org/10.1007/s002329900401

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