CONFLUENT MONOLAYERS OF BILE-DUCT EPITHELIAL-CELLS WITH TIGHT JUNCTIONS

The culture of fully differentiated intrahepatic bile duct epithelial cells (IBDECs) to use as a model for the in vivo intrahepatic biliary tract has not been established, IBDECs from normal rat livers were gro wn on a collagen-coated permeable filter and formed a confluent monola yer 7 days after being plated. Positive reactions for cytokeratin-19 a nd retained gamma-glutamyl transpeptidase (GGTP) activity were shown. The transepithelial electrical resistance between the apical and the b asolateral compartment culture chambers increased with the culture age and plateaued after the 7th day, The resulting cultured cells display ed a number of characteristics. (1) The cells formed a thin, continuou s monolayer and displayed microvilli on the apical surface and junctio nal complexes between the cells, consistent with in vivo IBDECs. (2) C ells cultured for more than 7 days prevented the passage of horseradis h peroxidase (HRP) and ruthenium red through paracellular pathways. (3 ) Seven-day-old cultures displayed a mean transepithelial electrical r esistance of 137.3 Ohm . cm(2) , which decreased by 27.1% from its ini tial level after cell treatment with ethylenediamineteeraacetic acid ( EDTA), These results indicate that confluent IBDEC monolayers are well differentiated and polarized with tight junctions (TJs) between the c ells. These cell monolayers can provide a useful and relevant model fo r the in vitro study of various in vivo bile duet phenomena.