Vectorial transport of bile acids in immortalized mouse bile duct cells

In ileal epithelial cells, apical sodium-dependent bile acid transporter (ASBT) is responsible for the uptake of bile acids from the lumen. Furthermore, ASBT is expressed in the apical plasma membrane of intrahepatic bile duct cells (BECs). Using cultured immortalized mouse intrahepatic BECs that form monolayers or cysts, vectorial transport of bile acids was studied. [3H]-taurocholic acid ([3H]-TCA) was transported through monolayers transcellularly almost exclusively from the apical to the basolateral side in a Na(+)- and a temperature-dependent manner. Transport of [3H]-TCA was inhibited by 59.3+/-18.6% in the presence of taurochenodeoxycholic acid. Uptake of lysyl fluorescein-conjugated bile acid, Cholyl-[Nepsilon-NBD]-lysine, was seen in a Na(+)- and a temperature-dependent manner from the apical side of BECs that form monolayer or cysts. Reverse transcription-polymerase chain reaction for mRNAs in the cells showed presence of mRNAs for ASBT and farnesoid X receptor (FXR), a nuclear bile acid receptor. In conclusion, intrahepatic BECs transport bile acids mainly from the apical to the basolateral side in concert with ASBT and maybe FXR in the cells.