Loss of fenamate-activated K+ current from epithelial cells during corneal wound healing.

PURPOSE The corneal epithelium provides a barrier between the external environment and the cornea. It also serves as an ion transporting epithelium. Because of its proximity with the external environment, the corneal epithelium is frequently injured through physical or chemical insult. The purpose of this study was to determine whether corneal epithelial cell whole-cell currents change during corneal wound healing as the author of the present study has previously reported for corneal keratocytes and endothelial cells. METHODS Rabbit corneal epithelial cells were injured by scraping, heptanol exposure, or freezing. The epithelium was allowed to heal for 12 to 74 hours. Cells were dissociated from corneas, and whole-cell currents were examined using the amphotericin-perforated-patch technique. RESULTS Cells from the wounded corneal groups had significantly increased capacitance values, indicating increased surface area compared with that of control cells. As previously reported, the primary control whole-cell current was a fenamate-activated K+ current. An inwardly rectifying K+ current and a Cl- current were also observed. In epithelial cells from heptanol-wounded corneas, these conductances were generally unchanged. In cells from scrape- and freeze-wounded corneas, however, the fenamate-activated current was absent or significantly attenuated. CONCLUSIONS As they do in corneal keratocytes and endothelial cells, K+ channels disappear during some models of corneal epithelial wound healing. In addition, cell capacitance, a measurement of cell surface area, increases. These results suggest that substantial K+ channel activity is not required for in vivo epithelial cell proliferation during corneal wound healing.