Effect of bicarbonate, pH, methazolamide and stibenes on the intracellular potentials of cultured bovine corneal endothelial cells

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Abstract
Micropuncture of cultured bovine corneal endothelial cells led to registrations stable for hours. Intracellular potentials were mainly in the range of −40 to −55 mV, average 46.3±0.6 mV (sem). Changes of extracellular [HCO 3 − ] led to voltage transients, their amplitude depending logarithmically on [HCO 3 − ] with a mean slope of 37.3±8.8 (sd) mV. After removal of bicarbonate/CO2, a steady-state depolarization was seen. This steady-state depolarization, but not the voltage transients, could be reduced by 1mm Ba++. After removal of bicarbonate, the voltage response to changes of extracellular potassium was reduced. Alteration of pH i induced by permeable buffers (butyrate, glycodiazine and ammonium) also resulted in voltage transients, internal acidification being correlated with a hyperpolarization, and internal alkalinization with a depolarization. Also changes of external pH caused voltage responses, alkalinization causing a hyperpolarization, acidification a depolarization. Methazolamide, an inhibitor of carbonic anhydrase, as well as stilbenes (SITS or DIDS) caused a reduction of the voltage response to HCO 3 − and pH. Their effects were additive. It is suggested that corneal endothelial cells possess one or two electrogenic transporters for HCO 3 − or related species, one of which is inhibitable by stilbenes.