Volume-activated chloride currents in pancreatic duct cells.
We have used the patch clamp technique to study volume-activated Cl- currents in the bicarbonate-secreting pancreatic duct cell. These currents could be elicited by a hypertonic pipette solution (osmotic gradient 20 mOsm/l), developed over about 8 min to a peak value of 91 +/- 5.8 pA/pF at 60 mV (n = 123), and were inhibited by a hypertonic bath solution. The proportion of cells which developed currents increased from 15% in freshly isolated ducts to 93% if the ducts were cultured for 2 days. The currents were ATP-dependent, had an outwardly rectifying current/voltage (I-V) plot, and displayed time-dependent inactivation at depolarizing potentials. The anion selectivity sequence was: ClO4 = I = SCN > Br = NO3 > Cl > F > HCO3 > gluconate, and the currents were inhibited to a variable extent by DIDS, NPPB, dideoxyforskolin, tamoxifen, verapamil and quinine. Increasing the intracellular Ca2+ buffering capacity, or lowering the extracellular Ca2+ concentration, reduced the proportion of duct cells which developed currents. However, removal of extracellular Ca2+ once the currents had developed was without effect. Inhibiting protein kinase C (PKC) with either the pseudosubstrate PKC (19-36), calphostin C or staurosporine completely blocked development of the currents. We speculate that cell swelling causes Ca2+ influx which activates PKC which in turn either phosphorylates the Cl- channel or a regulatory protein leading to channel activation.
Verdon
B
B
Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, UK.
Winpenny
J P
JP
Whitfield
K J
KJ
Argent
B E
BE
Gray
M A
MA
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000838:Anions / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D048429:Cell Size; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D066298:In Vitro Techniques; D017136:Ion Transport; D008564:Membrane Potentials; D010183:Pancreatic Ducts / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D000838:Anions; D018118:Chloride Channels; D002712:Chlorides; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium