REGULATION OF INTRACELLULAR PH BY IMMORTALIZED HUMAN INTRAHEPATIC BILIARY EPITHELIAL-CELL LINES

We have produced continuous cell lines using retroviral transduction o f SV40 large T antigen into human intrahepatic biliary epithelial (IBE ) cells from three different normal individuals. These IBE cell Lines grow in a hormone-supplemented medium in the presence of NIH/3T3 fibro blast coculture. These cells maintain their epithelial appearance and are positive for the biliary-specific markers cytokeratins 7 and 19 an d gamma-glutamyl transpeptidase while being negative for the hepatocyt e markers albumin and asialoglycoprotein receptor. To evaluate ion tra nsport pathways in IBE cell lines, we utilized intracellular pH (pH(i) ) measurements obtained using the intracellular fluorescent indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. In the absence of H CO3--CO2, an amiloride-sensitive Na+-H+ exchanger participated in the regulation of basal pH(i). In the presence of HCO3-CO2, a 4,4'-diisoth iocyanostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na-, Cl-, and H CO3--dependent acid extrusion mechanism accounted for similar to 60% o f pH(i) recovery from acidic pH(i); this mechanism is most consistent with the presence of a Na-dependent Cl--HCO3- exchanger (Na+HCO3-Cl-H). Under basal conditions, Cl- depletion revealed a DIDS-sensitive alk alinization consistent with a Na-independent Cl--HCO3- exchanger. Thes e model systems will allow the opportunity to study the normal mechani sms of IBE function and to study the pathobiology of IBE processes in disease states.