FUNCTIONAL-CHARACTERIZATION OF CHOROID-PLEXUS EPITHELIAL-CELLS IN PRIMARY CULTURE

The objective of this study was to develop and evaluate a primary cult ure system for choroid plexus epithelial cells as an in vitro model fo r studying organic cation transport. Cells were dispersed from choroid plexus of neonatal rats by enzymatic digestion and grew as differenti ated monolayers when plated on solid or permeable support. Electron mi croscopy showed that cultured cells were morphologically similar to in tact choroid plexus epithelium, having apical tight junctions between cells, numerous mitochondria, basal nuclei and apical microvilli and c ilia, As previously demonstrated for intact choroid plexus, immunocyto chemistry showed that Na+,K+-ATPase was localized to the apical membra ne, and GLUT-1, the facilitative glucose transporter, was localized to the basolateral membrane of cultured cells. Apical transport of L-pro line by cultured cells was mediated by a sodium-dependent, electrogeni c process, as in whole tissue. C-14-Tetraethylammonium (TEA), a protot ypic organic cation, was accumulated by isolated choroid plexus in a t ime-dependent manner; uptake was inhibited by tetrapentylammonium (TeP A). In cultured cells, apical TEA transport was mediated by a saturabl e process coupled to cellular metabolism. Unlabeled TEA and other orga nic cations (TePA, N-1-methylnicotinamide and mepiperphenidol) inhibit ed TEA transport; the organic anion, p-aminohippurate, had no effect. Finally, TePA-sensitive transport of C-14-TEA was stimulated after pre loading the cells with unlabeled TEA. Based on the morphological, bioc hemical and functional properties of these cultured cells, we conclude that this primary culture system should be an excellent in vitro mode l for experimental characterization of choroid plexus function.