Calcium-activated potassium conductances on cultured nontransformed dog pancreatic duct epithelial cells.
Pancreatic duct epithelial cells (PDECs) mediate the pancreatic secretion of fluid and electrolytes. Membrane K+ channels on these cells regulate intracellular K+ concentration; in combination with the Na+/H+ antiport and Na+,K+ adenosine triphosphatase (ATPase), they may also mediate serosal H+ secretion, balancing luminal HCO3- secretion. We describe the K+ conductances on well-differentiated and functional nontransformed cultured dog PDECs. Through 86Rb+ efflux studies, we demonstrated Ca(2+)-activated K+ channels that were stimulated by A23187, thapsigargin, and 1-ethyl-2-benzimidazolinone, but not forskolin. These conductances also were localized on the basolateral membrane because 86Rb+ efflux was directed toward the serosal compartment. Of the K+ channel blockers, BaCl2, charybdotoxin, clotrimazole, and quinidine, but not 4-aminopyridine, apamin, tetraethylammonium, or iberiotoxin, inhibited 86Rb+ efflux. This efflux was not inhibited by amiloride, ouabain, and bumetanide, inhibitors of the Na+/H+ antiport, the Na+,K(+)-ATPase pump, and the Na+,K+,2Cl- cotransporter, respectively. When apically permeabilized PDEC monolayers were mounted in Ussing chambers with a luminal-to-serosal K+ gradient, A23187 and 1-ethyl-2-benzimidazolinone stimulated a charybdotoxin-sensitive short-circuit current (Isc) increase. Characterization of K+ channels on these cultured PDECs, along with previous identification of Cl- channels (1), further supports the importance of these cells as models for pancreatic duct secretion.
Nguyen
T D
TD
University of Washington, Seattle, USA. t1nguyen@u.washington.edu
Moody
M W
MW
D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002120:Calcium Channel Agonists; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D003022:Clotrimazole / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004285:Dogs; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000502:physiology; D010183:Pancreatic Ducts / Q000166:cytology* / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology; D012414:Rubidium Radioisotopes / Q000378:metabolism
D001562:Benzimidazoles; D002120:Calcium Channel Agonists; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D018999:Charybdotoxin; D005576:Colforsin; D000001:Calcimycin; D003022:Clotrimazole; D011802:Quinidine; C102635:1-ethyl-2-benzimidazolinone; D002118:Calcium