Volume-activated chloride currents in pancreatic duct cells

• Published in: The Journal of membrane biology 1995-09, Vol.147 (2), p.173-183
• Main Authors: Verdon, B, Winpenny, J P, Whitfield, K J, Argent, B E, Gray, M A
• Format: Article
• Language: English
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Adenosine Triphosphate - metabolism; Animals; Anions - pharmacology; Calcium - metabolism; Calcium - pharmacology; Cell Size; Chloride Channels - antagonists & inhibitors; Chloride Channels - drug effects; Chloride Channels - metabolism; Chlorides - metabolism; In Vitro Techniques; Ion Transport; Membrane Potentials; Pancreatic Ducts - cytology; Pancreatic Ducts - metabolism; Phosphorylation; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Rats; Rats, Wistar
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/bf00233545

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.