PROPERTIES OF WHOLE-CELL IONIC CURRENTS IN CULTURED HUMAN CORNEAL EPITHELIAL-CELLS

PURPOSE. To identify and partially characterize the ionic currents con tributing to the whole-cell conductance of cultured human corneal epit helial cells. METHODS. Epithelial cells were scraped from human donor corneas and cultured for use in patch-clamp experiments. Amphotericin B and the perforated-patch configuration were used to measure whole-ce ll currents in cells isolated from confluent monolayers. RESULTS. Cell monolayers exhibited cobblestone morphology and were immunopositive f or corneal epithelium-specific cytokeratin. Single cells had a capacit ance of 21 +/- 2 pF and expressed similar types of ionic currents rega rdless of passage number. In descending order of frequency of occurren ce, cells exhibited a nonselective cation current active at depolarize d voltages and insensitive to Ba2+ and Gd3+; an outwardly rectifying K C current active at depolarized voltages, stimulated by flufenamic aci d and inhibited by tetraethylammonium; a voltage-gated inward Na+ curr ent; an outwardly rectifying K+ current active at hyperpolarized volta ges, stimulated by flufenamic acid, blocked by Ba2+, and insensitive t o diltiazem; an inwardly rectifying K+ current; and a nonselective cat ion current inhibited by flufenamic acid. CONCLUSIONS. Our results are consistent with those in previous studies of noncultured epithelia fr om rabbit and human corneas showing an outwardly rectifying K+ current active at hyperpolarized voltages and a nonselective cation current a ctive at depolarized voltages and insensitive to Ba2+. These data sugg est cultured cells may be useful in determining the physiological role of ion channels in corneal epithelia and may aid in the development o f a cell-based model for the examination of the effects of wounding an d toxic agents on the human cornea.