TIGHT JUNCTIONS AND PARACELLULAR PERMEABILITY IN CULTURED BOVINE CORNEAL ENDOTHELIAL-CELLS

Intramembrane specializations of cultured bovine corneal endothelial c ells were studied with thin section and freeze-fracture electron micro scopy and related to the paracellular permeability and the transendoth elial resistance (Rt) of the monolayers. The following intercellular j unctions were found: single and discontinuous networks of tight juncti ons (TJ) which girdle the apico-lateral cell perimeter incompletely, g ap junctions, and membrane undulations suggesting intermediate junctio ns. The macromolecular tracer ruthenium red penetrated into the latera l intercellular space beyond the level of the incomplete belt of TJ. R (t) of these monolayers was 20.9 +/- 1.0 Omega.cm(2). Protamine induce d a reversible increase of R(t) to 118+/-5% of its control value. We c onclude that incomplete belts of TJ may be the morphological counterpa rt of the high paracellular permeability of this monolayer and functio nally and morphologically resemble those of their native endothelium. Cultured corneal endothelial cells are an excellent model for studying the influence of incomplete belts of TJ on paracellular permeability of cells.