Non-selective cation channel on pancreatic duct cells.
We have identified a non-selective cation channel on pancreatic duct cells. These epithelial cells secrete the bicarbonate ions found in pancreatic juice; a process controlled by the hormone secretin, which uses cyclic AMP as an intracellular messenger. The non-selective channel is located on both apical and basolateral plasma membranes of the duct cell, is equally permeable to sodium and potassium, and has a linear I/V relationship with a single-channel conductance of about 25 pS. Channel opening requires the presence of 1 microM Ca2+ on the cytoplasmic face of the membrane, and is also increased by depolarization. Intracellular ATP, ADP, magnesium, and a rise in pH all decreased channel activity. The channel was not affected by 10 mM TEA, 1 mM Ba2+ or 0.5 mM decamethonium applied to the cytoplasmic face of the membrane, but 0.5 mM quinine caused a flickering block which was more pronounced at depolarizing potentials. We observed the channel only rarely in cell-attached patches on unstimulated duct cells, and acute exposure to stimulants did not cause channel activation. However, after prolonged stimulation, the proportion of cell-attached patches containing active channels was increased 9-fold. The role of this channel in pancreatic duct cell function remains to be elucidated.
Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, U.K.
M A
MA
Gray
B E
BE
Argent
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D010179:Pancreas / Q000737:chemistry* / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D015290:Second Messenger Systems; D012633:Secretin / Q000494:pharmacology
D007473:Ion Channels; D012633:Secretin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011803:Quinine; D000242:Cyclic AMP; D008274:Magnesium; D002118:Calcium