Inwardly rectifying, voltage-dependent and resting potassium currents in rat pancreatic acinar cells in primary culture.
1. In exocrine pancreatic acinar cells in primary culture an inwardly rectifying, a voltage-dependent and a permanent resting K+ current were characterized. 2. Inwardly rectifying K+ currents could be elicited by elevation of the extracellular K+ concentration. The K+ inward currents were almost completely blocked by 5 mM Ba2+, whereas 10 mM TEA+ had only a partial effect. 3. Depolarizing voltage steps from negative clamp potentials evoked transient activation of a voltage-dependent K+ current. This voltage-dependent current could be blocked by 10 mM TEA+ and 1 mM 4-aminopyridine, but not by 5 mM Ba2+. 4. Neither the K+ inward rectifier nor the voltage-dependent K+ conductance produced a significant negative cell potential. Stable membrane potentials (-38.7 +/- 2.3 mV, n = 38) could only be recorded on cell clusters (> or = 5 cells). 5. Cell clusters, in contrast to single cells, had a permanent resting K+ conductance in addition to the inward rectifier and the voltage-dependent current. This resting K+ conductance was not blocked by TEA+, Ba2+, 4-aminopyridine or by the chromanol 293B. 6. Cytosolic alkalization by addition of NH4Cl to the bath solution decreased the resting K+ current. In parallel, electrical uncoupling of the cells and breakdown of the resting potential could be observed. The same effects could be produced when the cells were uncoupled by 0.2-1.0 mM n-octanol. It can be concluded that cell coupling is essential for maintenance of stable resting membrane potentials in pancreatic acinar cells.
Schmid
A
A
Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany. schmid@med-ph.uni-sb.de
Feick
P
P
Schulz
I
I
D015761:4-Aminopyridine / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D000442:Octanols / Q000494:pharmacology; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011422:Propionates / Q000494:pharmacology; D051381:Rats; D019789:Tetraethylammonium / Q000494:pharmacology
D000442:Octanols; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011422:Propionates; D000643:Ammonium Chloride; D019789:Tetraethylammonium; D008536:Meglumine; D015761:4-Aminopyridine; D011188:Potassium