[FUNCTIONAL LINK BETWEEN TRANSPORT PARAMETERS OF MDCK1 CELLS MONOLAYER AND THEIR ACTIN CYTOSKELETON ORGANIZATION]

On MDCK1 cell monolayer, dynamics of the spatial organization of actin cytoskeleton and dynamics of trans-epithelial electrical resistance (TEER) have been studied upon exposure of arginine-vasopressin (AVP) and protein-kinase A (PKA) activator forskolin. It has been found that exposure to these physiologically active compounds causes fibrillary actin depolymerization (both in apical and in basal cytoplasm) and, simultaneously, significant decrease in the cell monolayer trans-epithelial electrical resistance. TEER decrease indicates the stimulation of ions and water flow across the cell monolayer. In order to clarify pathways of movement of ions and water across MDCK monolayer, we have carried out an immunofluoresence study of claudin 1 and 2 localization in the tight junctions of MDCK ATCC cells (low TEER) and MDCK1 cells (high TEER). We have demonstrated that in the tight junctions of MDCK ATCC cells both claudin 1 and claudin 2 are present. In MDCK1 cells tight junctions, claudin 1 is localized and pore-forming claudin 2 is completely lacking. Under forskolin exposure to MDCK1 cells, no alterations in studied claudins distribution has been found. These data indicate that forskolin-induced TEER decrease is linked with alterations in trans-cellular, not in para-cellular, permeability of monolayer.