title: K+-conductance and electrogenic Na+/K+ transport of cultured bovine pigmented ciliary epithelium.
abstract: Using intracellular microelectrode technique, we investigated the changes in membrane voltage (V) of cultured bovine pigmented ciliary epithelial cells induced by different extracellular solutions. (1) V in 213 cells under steady-state conditions averaged -46.1 +/- 0.6 mV (SEM). (2) Increasing extracellular K+ concentration [( K+]o) depolarized V. Addition of Ba2+ could diminish this response. (3) Depolarization on doubling [K+]o was increased at higher [K+]o (or low voltage). (4) Removing extracellular Ca2+ decreased V and reduced the V amplitude on increasing [K+]o. (5) V was pH sensitive. Extra- and intracellular acidification depolarized V; alkalinization induced a hyperpolarization. V responses to high [K+]o were reduced at acidic extracellular pH. (6) Removing K+o depolarized, K+o readdition after K+ depletion transiently hyperpolarized V. These responses were insensitive to Ba2+ but were abolished in the presence of ouabain or in Na+-free medium. (7) Na+ readdition after Na+ depletion transiently hyperpolarized V. This reaction was markedly reduced in the presence of ouabain or in K+-free solution but unchanged by Ba2+. It is concluded that in cultured bovine pigmented ciliary epithelial cells K+ conductance depends on Ca2+, pH and [K+]o (or voltage). An electrogenic Na+/K+-transport is present, which is stimulated during recovery from K+ or Na+ depletion. This transport is inhibited by ouabain and in K+- or Na+-free medium.
authors.affiliation: Institut für Klinische Physiologie, Klinikum Steglitz der Freien Universität Berlin, Federal Republic of Germany.
authors.forename: H
authors.initials: H
authors.lastname: Helbig
authors.forename: C
authors.initials: C
authors.lastname: Korbmacher
authors.forename: M
authors.initials: M
authors.lastname: Wiederholt
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D002924:Ciliary Body / Q000502:physiology*; D004847:Epithelial Cells; D005110:Extracellular Space / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium