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Updated: Jul 23, 2026

Real Time Monitoring of Intracellular Bile Acid Dynamics Using a Genetically Encoded FRET-based Bile Acid Sensor
Published on: January 4, 2016
Evidence for an ATP-dependent bile acid transport protein other than the canalicular liver ecto-ATPase in rats
T T Luther1, P Hammerman, C M Rahmaoui
1Department of Medicine, University of California, San Francisco 94143-0538, USA.
Background & Aims:
Canalicular secretion is rate limiting in overall blood-to-bile transport of bile acids. Studies using transfected cells have implicated the canalicular ecto-adenosine triphosphatase (ecto-ATPase) in adenosine triphosphate (ATP)-dependent bile acid transport. However, the structural features of this ecto-ATPase are not those anticipated for an in-to-out ATP-dependent transporter. The aim of this study was to explore the possible existence of an ATP-dependent bile acid transport mechanism distinct from ecto-ATPase.
Methods:
Bile acid transport activity and ecto-ATPase expression were analyzed in primary rat hepatocytes, rat hepatoma HTC cells, and specially adapted HTC (HTC-R) cells using plasma membrane vesicles and Northern blot, slot blot, ribonuclease protection assay, and Western blot analyses.
Results:
Plasma membranes isolated from HTC-R cells exhibited ATP-dependent taurocholate transport, which was many-fold greater than that in HTC cells. Hepatocytes showed the highest transport rates. Protein and RNA analyses showed very low expression of ecto-ATPase in HTC and HTC-R cells compared with hepatocytes. There was no difference between the two cell types at both the RNA and protein level.
Conclusions:
These findings show the presence in HTC-R cells and, apparently in hepatocytes, of one or more proteins other than the ecto-ATPase that mediate ATP-dependent transport of bile acids.
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