The permeability of rabbit and human corneal endothelium.

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Abstract
The fluxes of Na, Cl and HCO3 across endothelium plus stroma and then stroma alone were measured in the direction from lens-side to tear-side in rabbit and human corneas in vitro to measure passive permeabilities. The results were used to calculate the permeability of the endothelium. Hodgkin''s equation was then used to calculate the partial electrical conductivity of each ion crossing the endothelium. The summated electrical conductivities of Na, Cl, and HCO3 were equal to 89 .+-. 8% of the measured electrical conductivity, suggesting that the ions diffuse independently across the endothelium in the direction lens-side to tear-side. Stereological analysis of the intercellular spaces supports the idea that the ions permeate through this route and that the physical shape of the species determines almost entirely the permeability of the endothelial layer. Trans-endothelial Na an Cl permeabilities were found to be nearly equal, which may be explained by supposing the intercellular spaces include a cation exchanger of fixed negative charge capacity around 60 meq l-1 intercellular fluid.

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