Differential regulation of tight junction permeability during development of the retinal pigment epithelium.
The retinal pigment epithelium (RPE) is an epithelial region of the blood-brain barrier. During embryogenesis, permeability of the barrier gradually decreases. A culture model of RPE development revealed differences in how tight junctions regulate the paracellular diffusion of ionic and nonionic solutes (Ban Y and Rizzolo LJ. Mol Vis 3: 18, 1997). To examine these differences, the permeation of ionic and nonionic monosaccharides was compared with mannitol, and the permeation of the alkali metals was compared with sodium. The order of permeation was 3-O-methlyglucose = glucosamine = mannitol > N-acetylneuraminic acid. The ratio of N-acetylneuraminic acid to mannitol permeability decreased with embryonic age of the RPE or exposure to retinal-conditioned medium. Neither the ratio nor the permeability was affected by inhibiting transcytosis. The ratio increased if tight junctions were disrupted in low-calcium medium. The permeation of cations followed the sequence cesium > rubidium > potassium = sodium > lithium and was unaffected by embryonic age or retinal-conditioned medium. These results are considered in terms of a model in which the size distribution, charge, or number of open junctional pores could be modulated. It suggests that different subpopulations of pores can be regulated independently during development.
Ban
Y
Y
Departments of Surgery and of Ophthalmology and Visual Science, Yale University, New Haven, Connecticut 06520-8062, USA.
Rizzolo
L J
LJ
D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D008353:Mannitol / Q000493:pharmacokinetics; D008672:Metals, Alkali / Q000493:pharmacokinetics; D009005:Monosaccharides / Q000493:pharmacokinetics; D010539:Permeability; D010857:Pigment Epithelium of Eye / Q000196:embryology* / Q000378:metabolism*; D012964:Sodium / Q000493:pharmacokinetics; D019108:Tight Junctions / Q000378:metabolism*
D008672:Metals, Alkali; D009005:Monosaccharides; D008353:Mannitol; D012964:Sodium