Barrier function of porcine choroid plexus epithelial cells is modulated by cAMP-dependent pathways in vitro

In the present paper, we demonstrate that the barrier properties of primary cultured epithelial cells isolated from porcine choroid plexus are regulat ed by cAMP-dependent signal transduction pathways in vitro. Triggering cAMP -connected cascades in cell layers grown on permeable filters with cAMP-ana logues or forskolin led to a significant increase of transepithelial electr ical resistances and a pronounced reduction in the permeation rate of a 4 k Da-dextran probe. In dose-response experiments using the cAMP-analogue 8-(4 -chlorophenylthio)-cAMP transepithelial electrical resistances were observe d to increase above a threshold concentration ranging between 10(-5.5),and 10(-5) M. Additional impedance studies performed with confluent cell layers grown on gold-film electrodes revealed that the observed changes in transe pithelial resistances and presumably also in macromolecular permeation rate s were not entirely caused by a reinforcement of intercellular junctions bu t also contained contributions from changes in the cell-substrate adhesion pattern. These inherent contributions to the electrical resistance and macr omolecular permeability are caused by a restricted diffusion pathway betwee n basal plasma membrane and culture substrate that have to be considered in data analysis, especially when leaky cell layers on filter substrates with low pore densities are used. (C) 2000 Elsevier Science B.V, All rights res erved.