Determination of pathways for sodium movement across corneal endothelial cell derived plasma membrane vesicles

A bovine corneal endothelial cell plasma membrane vesicle preparation was used to investigate passive Na+ transport across the plasma membrane of these cells. Sodium accumulation rate into the vesicle was not dependent on the presence of HCO3- or a HCO3- gradient, but was stimulated by a trans-vesicle pH gradient. Amiloride, furosemide and DIDS all reduced the rate of Na+ accumulation. The data indicate the presence of at least two independent pathways for passive sodium movement across the vesicle: the first probably via a Na+/H+ exchanger and the second a furosemide inhibitable Na+ entry mechanism. No evidence was found for direct Na(+)-HCO3- coupled transport.