Properties of whole-cell ionic currents in cultured human corneal epithelial cells

PURPOSE. To identify and partially characterize the ionic currents contributing to the whole-cell conductance of cultured human corneal epithelial 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-cell currents in cells isolated from confluent monolayers. RESULTS. Cell monolayers exhibited cobblestone morphology and were immunopositive for corneal epithelium-specific cytokeratin. Single cells had a capacitance of 21 ≠ 2 pF and expressed similar types of ionic currents regardless of passage number. In descending order of frequency of occurrence, cells exhibited a nonselective cation current active at depolarized voltages and insensitive to Ba²⁺ and Gd³⁺; an outwardly rectifying K⁺ current active at depolarized voltages, stimulated by flufenamic acid and inhibited by tetraethylammonium; a voltage-gated inward Na⁺ current; an outwardly rectifying K⁺ current active at hyperpolarized voltages, stimulated by flufenamic acid, blocked by Ba²⁺, and insensitive to diltiazem; an inwardly rectifying K⁺ current; and a nonselective cation current inhibited by flufenamic acid. CONCLUSIONS. Our results are consistent with those in previous studies of noncultured epithelia from rabbit and human corneas showing an outwardly rectifying K⁺ current active at hyperpolarized voltages and a nonselective cation current active at depolarized voltages and insensitive to Ba²⁺. These data suggest cultured cells may be useful in determining the physiological role of ion channels in corneal epithelia and may aid in the development of a cell-based model for the examination of the effects of wounding and toxic agents on the human cornea.