Abstract
Drug-induced cholestasis can result from the inhibition of biliary efflux of bile acids in the liver. Drugs may inhibit the hepatic uptake and/or the biliary efflux of bile acids resulting in an increase in serum concentrations. However, it is the intracellular concentration of bile acids that results in hepatotoxicity, and thus serum concentrations may not necessarily be an appropriate indicator of hepatotoxicity. In this study, sandwich-cultured rat hepatocytes were used as an in vitro model to assess the cholestatic potential of drugs using deuterium-labeled sodium taurocholate (d8-TCA) as a probe for bile acid transport. Eight drugs were tested as putative inhibitors of d8-TCA uptake and efflux. The hepatobiliary disposition of d8-TCA in the absence and presence of drugs was measured by using liquid chromatography/tandem mass spectrometry, and the accumulation (hepatocytes and hepatocytes plus bile), biliary excretion index (BEI), and in vitro biliary clearance (Clbiliary) were reported. Compounds were classified based on inhibition of uptake, efflux, or a combination of both processes. Cyclosporine A and glyburide showed a decrease in total (hepatocytes plus bile) accumulation, an increase in intracellular (hepatocytes only) accumulation, and a decrease in BEI and Clbiliary of d8-TCA, suggesting that efflux was primarily affected. Erythromycin estolate, troglitazone, and bosentan resulted in a decrease in accumulation (total and intracellular), BEI, and Clbiliary of d8-TCA, suggesting that uptake was primarily affected. Determination of a compound's relative effect on bile acid uptake, efflux, and direct determination of alterations in intracellular amounts of bile acids may provide useful mechanistic information on compounds that cause increases in serum bile acids.
Footnotes
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.109.028407.
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- NTCP
- sodium taurocholate cotransporting polypeptide
- BSEP
- bile salt export protein
- SCH
- sandwich-cultured hepatocytes
- TAO
- troleandomycin
- d8-TCA
- deuterium-labeled taurocholic acid
- LC/MS/MS
- liquid chromatography/tandem mass spectrometry
- BEI
- biliary excretion index
- Clbiliary
- in vitro biliary clearance
- SCRH
- sandwich-cultured rat hepatocytes.
- Received June 17, 2009.
- Accepted November 4, 2009.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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