EFFECTS OF PH ON THE POTASSIUM CURRENT IN RABBIT CORNEAL EPITHELIAL-CELLS

The effects of pH on K+ conductance were measured using the amphoteric in perforated-patch whole cell voltage-clamp technique in freshly disp ersed rabbit corneal epithelial cells. Bath perfusion with pH 6.00 Rin ger solution after standard Ringer solution (pH 7.35) increased outwar d K+-selective current (I-K) from 120 +/- 29 to 312 +/- 64 pA during a step depolarization to +50 mV and hyperpolarized the resting membrane potential (E(m)) rom -52 +/- 5 to -62 +/- 3 mV (n = 15, P less than o r equal to 0.05). Increasing bath pH to 8.5 decreased I-K from 183 +/- 40 to 114 +/- 35 pA (n = 6, P less than or equal to 0.05) and depolar ized E(m) from -63 +/- 6 to -53 +/- 5 mV (n = 6, P less than or equal to 0.05). Intracellular acidification using the weak electrolyte (NH4) (2)SO4 also increased I-K from 83 +/- 15 to 183 +/- 20 pA (n = 4, P = 0.01) and hyperpolarized E(m) from -51 +/- 8 to -68 +/- 6 mV (P = 0.00 2). Intracellular alkalinization reduced I-K to 66 +/- 10 pA and depol arized E(m) to -36 +/- 8 mV (P = 0.009). Single channel studies in per forated outside-out vesicles showed that a decrease in bath pH from 7. 35 to 6.00 was accompanied by an increase in the single channel open p robability (NPo) from 0.43 to 0.64 at an E(m) of 15 mV. NPo was also i ncreased in cell-attached patches. The unitary conductance, measured f rom -100 to +100 mV, was not changed. These results indicate that pH m odulates I-K in rabbit corneal epithelial cells by changes in NPo.