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Inwardly rectifying, volt age‐dependent and resting potassium currents in rat pancreatic acinar cells in primary culture
Author(s) -
Schmid Andreas,
Feick Peter,
Schulz Irene
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.259be.x
Subject(s) - depolarization , resting potential , biophysics , chemistry , membrane potential , 4 aminopyridine , tetraethylammonium , inward rectifier potassium ion channel , patch clamp , conductance , potassium channel , potassium , endocrinology , medicine , ion channel , biochemistry , biology , physics , receptor , organic chemistry , condensed matter physics
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 m m Ba 2+ , whereas 10 m m 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 m m TEA + and 1 m m 4‐aminopyridine, but not by 5 m m Ba 2+ . 4 Neither the K + inward rectifier nor the voltage‐dependent K + conductance produced a significant negative cell potential. Stable membrane potentials (–38.7 ± 2.3mV, n = 38 ) could only be recorded on cell clusters (≥ 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 + , Ba 2+ , 4‐aminopyridine or by the chromanol 293B. 6 Cytosolic alkalization by addition of NH 4 Cl 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 m m n‐octanol. It can be concluded that cell coupling is essential for maintenance of stable resting membrane potentials in pancreatic acinar cells.