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(Investigative Ophthalmology and Visual Science. 2001;42:1847-1854.)
© 2001 by The Association for Research in Vision and Ophthalmology, Inc.

Two Types of K+ Currents Modulated by Arachidonic Acid in Bovine Corneal Epithelial Cells

Masayuki Takahira, Norimasa Sakurada, Yasunori Segawa and Yutaka Shirao

From the Department of Ophthalmology, Kanazawa University School of Medicine, Japan.

PURPOSE. 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 µM) 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.




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