Whole-cell potassium current in rabbit corneal epithelium activated by fenamates

Rabbit corneal epithelium contains a large-conductance, potassium-selective channel, which is a major contributor to the whole-cell current. In perforated-patch recordings of the macroscopic current, the isolated cells studied had resting voltages of -41 +/- 20 mV and capacitances of 5.8 +/- 2.6 pF (mean +/- SD for n = 255). Activation of the channels was weakly voltage dependent. They opened at about -100 mV and reached an open probability of about 0.2 at +100 mV. The current was blocked by millimolar concentrations of external Ba2+ and quinidine. Diltiazem also blocked when applied to the external surface of the membrane. Nonsteroidal anti-inflammatory agents of the fenamate group were powerful activators of the channel at submillimolar concentrations when applied either to the inside or the outside of the channels. The mechanism of action which leads to his activation is not yet known.