Modulation of rabbit corneal epithelial cell proliferation by growth factor-regulated K(+) channel activity.
We characterized the dependence of the mitogenic response by rabbit corneal epithelial (RCE) cells to serum containing growth factors on K(+) channel activation. Using both cell-attached and nystatin-perforated patch-clamp configurations, a K(+) channel was identified whose current-voltage relationship is linear with a single-channel conductance of 31 pS. Its activity was barely detectable following 24 h serum starvation. Exposure of starved cells to either 10% FBS, 5 ng/ml epidermal growth factor (EGF) or 2 n M endothelin-1 (ET-1) continuously increased its activity within 30 min by 40%, 54% and 29%, respectively. EGF and ET-1 in combination had additive effects on such activity. Application of 100 micro M 4-aminopyridine (4-AP), a K(+) channel blocker, inhibited serum-stimulated K(+) channel activity by 85%. DNA synthesis was markedly stimulated by serum, whereas incubation with either 4-AP (200 micro M) or Ba(2+) (1 m M) suppressed this increase by 51% and 23%, respectively, whereas 5 m M tetra ethyl ammonium (TEA) had no effect. Taken together, growth factor-induced increases in proliferation are dependent on K(+) channel stimulation. As the increases in K(+) channel activity induced by ET-1 and EGF were additive, these mitogens may stimulate K(+) channel activity through different signaling pathways linked to their cognate receptors.
Roderick
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C
Division of Molecular Medicine, Harbor-UCLA Medical Center, School of Medicine University of California, Los Angeles, Torrance, CA 90502, USA.
Reinach
P S
PS
Wang
L
L
Lu
L
L
D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000378:metabolism* / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development*; D006706:Homeostasis / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008934:Mitogens / Q000378:metabolism / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D019789:Tetraethylammonium
D019332:Endothelin-1; D008934:Mitogens; D015221:Potassium Channels; D001464:Barium; D004815:Epidermal Growth Factor; D019789:Tetraethylammonium; D015761:4-Aminopyridine