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L. Ma, K. Kuang, P. Iserovich, J. Li, J. Fischbarg; Properties of the Tight Junction Relevant for Fluid Transport as Studied With Modulators . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2206.
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According to a recent hypothesis, the corneal endothelium removes water from the corneal stroma through the paracellular route via electro–osmotic coupling taking place in the tight junctions (TJ). Hence, we investigated the relationship between TJ electrical resistance and endothelial fluid transport.
ATP, dBcAMP, palmitoyl carnitine (PC), ouabain and poly–L–lysine (PLL) were used to modulate corneal endothelial fluid transport and TJ. We used the standard deepithelialized rabbit corneal preparation to determine fluid transport (FT). The corneal thickness was determined using an automated specular reflection (Dikstein–Maurice) microscope. Reagents were added when corneal thickness had stabilized after mounting (about 60 minutes). Transendothelial resistance (TER) was determined using cultured rabbit corneal endothelial cells (CRCEC) grown to full confluence for two weeks on 24 mm permeable membrane inserts.
The rates (um/h) of corneal stroma swelling and the TER (% of initial value) after 60 minutes of drugs application were:
If fluid transport is paracellular, opening of that route would increase FT. This is what we observe when using dBcAMP and ATP: fluid transport increases, and TER decreases.
If electro–osmosis is the driving force, changing the TJ zeta potential by treatment with the polycation PLL would disrupt electro–osmosis without significant effect on TER. This is what we observe.
If TJs are however disrupted (opened in an unspecific manner), one would expect both decreased TER and decreased FT, as we also observe.
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