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P. Iserovich, L. Ma, K. Kuang, J. Fischbarg; Pressure–Induced Streaming Potentials Across Corneal Endothelium Are Consistent With Electro–Osmotic Coupling . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2910.
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To ascertain the electro–osmotic (E–O) coupling ability of corneal endothelium. For this purpose, we explored streaming potentials (SP) developed across this layer upon application of a hydrostatic pressure difference.
We used cultured bovine and rabbit corneal endothelial cell layers grown on 12 mm Costar Transwell inserts. We also used in vitro rabbit corneal preparations à la Dikstein and Maurice (DM). Both cell layers and corneas were mounted in modified Ussing chambers (WPI); the bathing solutions contained bicarbonate and 10 mM HEPES, and were gassed with 95% air–5% CO2. We used a 4–electrode system (WPI; Ag–AgCl plus agar bridges), the chamber funnels were kept at 37 C, and the entire system of chamber and electrodes was enclosed in an incubator set at 37 C. Transendothelial electrical potential difference (PD) was recorded with a WPI DVC–1000, digitized and saved.
Hydrostatic pressure was always applied to the apical side of the endothelium. After a pressure step, the PD changed immediately; the direction of the SP thus generated was apical side negative. PD changes were linear with pressure changes, and were at least 1 µV per 1 cm H2O pressure change. SP’s were observed in some 20 culture inserts, and 6 rabbit corneal preparations. Consistent results were observed as long as the pressure applied did not exceed 60 cm H2O.
The direction of the induced streaming potentials is consistent with a negative effective zeta potential, in turn consistent with the predominant presence of negative fixed charges in the tight junctions. The presence and the direction of the streaming potentials support the hypothesis that the tight junctions are the site of electro–osmotic coupling in corneal endothelium.
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