Two types of K+ currents modulated by arachidonic acid in bovine corneal epithelial cells.
OBJECTIVE
Fenamate sensitivity of the large-conductance K+ current in the corneal epithelium suggests that K+ transport could be modulated by arachidonic acid (AA) and/or its metabolites, which also regulate corneal epithelial migration. The main purpose of this study was to investigate AA-induced modulation of K+ currents expressed in the bovine corneal epithelium.


METHODS
Freshly isolated bovine corneal epithelial cells were perfused with Ringer solution. Whole-cell currents were recorded by using either the conventional whole-cell-patch or the perforated-patch configuration.


RESULTS
Two distinct types of K+ currents dominated the whole-cell current. The first was a voltage-gated K+ current that was inactivated completely by membrane depolarization. The inactivating voltage-gated K+ current was largest in presumptive basal cells. The second was a noisy, sustained K+ current that was never inactivated and seemed to be a counterpart of the large-conductance K+ current reported in the rabbit corneal epithelium. External application of AA (5-20 microm) inhibited the inactivating voltage-gated K+ current and augmented the noisy, sustained K+ current. Identical dual modulation was induced by other fatty acids (e.g., palmitoleic acid) that are not substrates for enzymes in the AA cascade.


CONCLUSIONS
An inactivating voltage-gated K+ channel was identified for the first time in the corneal epithelium. AA and some fatty acids may directly activate the large-conductance K+ channel to augment its housekeeping functions in corneal epithelial cells.
Takahira
M
M
Department of Ophthalmology, Kanazawa University School of Medicine, Takara-Machi 13-1, Kanazawa 920-8640,Japan. takahira@kenroku.kanazawa-u.ac.jp
Sakurada
N
N
Segawa
Y
Y
Shirao
Y
Y
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D002417:Cattle; D004594:Electrophysiology / Q000379:methods; D019573:Epithelium, Corneal / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*
D015221:Potassium Channels; D016718:Arachidonic Acid; D011188:Potassium