title: Isolated bovine retinal pigment epithelial cells express delayed rectifier type and M-type K+ currents.
abstract: Outwardly rectifying K+ currents in freshly isolated bovine retinal pigment epithelial (RPE) cells were characterized using the whole cell and perforated-patch configurations of the patch-clamp technique. All cells exhibited a delayed rectifier type K+ current. This current had an activation threshold voltage of approximately -40 mV, activated with a sigmoidal trajectory, and inactivated completely over a period of several seconds. External tetraethylammonium (TEA) was an effective blocker of the delayed rectifier current [apparent dissociation constant (Kd) = 5.1 mM], but external Ba2+ was relatively ineffective. Approximately 24% of the cells also exhibited a sustained outwardly rectifying K+ current that became activated at voltages positive to approximately -80 mV. This current resembled the neuronal M-current. External Ba2+ was a potent blocker of this current (apparent Kd = 1.1 mM), but external TEA and Cs+ were relatively ineffective. These results indicate that freshly isolated bovine RPE cells express K+ currents of both the delayed rectifier and M types. The latter may contribute to the resting K+ conductances of the apical and basolateral membranes.
authors.affiliation: Department of Ophthalmology, University of Michigan, Ann Arbor 48105, USA.
authors.forename: M
authors.initials: M
authors.lastname: Takahira
authors.forename: B A
authors.initials: BA
authors.lastname: Hughes
mesh_terms: D000666:Amphotericin B; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002417:Cattle; D002586:Cesium / Q000494:pharmacology; D051668:Delayed Rectifier Potassium Channels; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010857:Pigment Epithelium of Eye / Q000502:physiology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D013757:Tetraethylammonium Compounds; D002586:Cesium; D001464:Barium; D019789:Tetraethylammonium; D000666:Amphotericin B