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 (SCRH) 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 evaluated as putative inhibitors of d8-TCA uptake and efflux. The hepatobiliary disposition of d8-TCA in the absence and presence of drugs was measured using LC/MS/MS and the accumulation (hepatocytes and hepatocytes plus bile), biliary excretion index (BEI) and in vitro biliary clearance (Clbiliary) were determined. 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), an increase in intracellular (hepatocytes only) accumulation, and a decrease in BEI and Clbiliary of d8-TCA suggesting 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 uptake was primarily affected. Determination of a compounds 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.
- ABC transporters
- bile acid transport
- biliary excretion
- drug transport
- drug-induced hepatotoxicity
- hepatic transport
- hepatic uptake
- hepatobiliary disposition
- hepatotoxicity
- liver toxicity
Footnotes
- Received June 30, 2009.
- Accepted November 4, 2009.
- The American Society for Pharmacology and Experimental Therapeutics