title: Characteristics of bicarbonate, sodium, and chloride fluxes in the rabbit corneal endothelium.
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 degrees 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 mM) 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 muEq/cm2/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.
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects / Q000378:metabolism*; D004727:Endothelium / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D000086:Acetazolamide