title: Potassium channel inhibition reduces cell proliferation in the GH3 pituitary cell line.
abstract: Potassium (K+) conductances are known to be involved in cell proliferation of a number of nonexcitable cell types. The nature of the mechanism by which K+ channel inhibition reduces cell proliferation has remained elusive despite intensive search. We investigated whether such a phenomenon could be demonstrated in excitable cells, using the GH3 pituitary cell line as a cell model. Our aims were: 1) to study the effect of K+ channel inhibition on the proliferation of GH3 cells; and 2) to investigate the putative intracellular signals involved in this inhibition. Tetraethylammonium chloride (TEA), a blocker of the calcium (Ca2+)-dependent K+ conductances of GH3, was found to reversibly inhibit cell proliferation, as measured by 3H-thymidine incorporation. Cell cycle block specifically occurred at the G1/S phase of the cell cycle. This inhibition of proliferation was observed for 1-4 mM TEA, which suppressed most of the Ca2+-activated K+ current and part of the inward rectifying K+ current, as shown by electrophysiological experiments. Increasing extracellular K+ concentrations with KCI also inhibited cell proliferation in a dose-dependent manner. Both TEA and KCl depolarized the cells and increased intracellular Ca2+ levels ([Ca2+]i), showing that, in this type of excitable cell, inhibition of cell proliferation can be associated with elevated Ca2+ levels. Ca2+ and membrane resting potential (MRP) were considered as possible messengers of this inhibition. Our results suggest that cell cycle arrest of GH3 cells by K+ channel block probably involves an additional pathway, distinct from those of Ca2+ and MRP.
authors.affiliation: Laboratoire de Neurophysiologie, CNRS UMR 5543, Université Victor Segalen-Bordeaux II, Bordeaux, France.
authors.forename: S
authors.initials: S
authors.lastname: Vaur
authors.forename: L
authors.initials: L
authors.lastname: Bresson-Bepoldin
authors.forename: B
authors.initials: B
authors.lastname: Dufy
authors.forename: S
authors.initials: S
authors.lastname: Tuffet
authors.forename: L
authors.initials: L
authors.lastname: Dufy-Barbe
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004594:Electrophysiology; D008564:Membrane Potentials / Q000502:physiology; D010902:Pituitary Gland / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000502:physiology; D026902:Potassium Channel Blockers; D011189:Potassium Chloride / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D013936:Thymidine / Q000493:pharmacokinetics
chemical_list: D026902:Potassium Channel Blockers; D019789:Tetraethylammonium; D011189:Potassium Chloride; D011188:Potassium; D002118:Calcium; D013936:Thymidine