Abstract
Unidirectional fluxes of bicarbonate, sodium and chloride were measured across the isolated rabbit corneal endothelium. Bicarbonate and sodium fluxes were measured between 13 and 37°C and were found to be temperature-sensitive. Ouabain (10 −6 m), which inhibits endothelial fluid transport, reduced the net bicarbonate flux by 32% but had no significant effect on sodium fluxes. Amiloride (10 −4 m) did not alter sodium transport, but slightly increased the unidirectional bicarbonate fluxes. Sodium fluxes were unchanged in chloride-free and potassium-free Ringer solutions, and net sodium transport was unaffected in the presence of carbonic anhydrase, acetazolamide, or low (5 m m) bicarbonate Ringer, but was reduced by 45% in bicarbonate-free Ringer. A net chloride flux was found in the same direction (stroma to aqueous) as bicarbonate and sodium. This chloride flux (2·18 μEq/cm 2/hr) was of the same magnitude as bicarbonate but was sodium-independent. These findings suggest that: (1) like bicarbonate and fluid transport, sodium transport is bicarbonate-dependent, temperature-sensitive, and chloride-independent; (2) sodium transport is not stoichiometrically coupled to bicarbonate; and (3) neither sodium nor bicarbonate transport are coupled to that of chloride.
Published Version
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