Abstract
This study examined the hepatobiliary disposition of troglitazone (TGZ) and metabolites [TGZ sulfate (TS), TGZ glucuronide (TG), and TGZ quinone (TQ)] over time in rat and human sandwich-cultured hepatocytes (SCH). Cells were incubated with TGZ; samples were analyzed for TGZ and metabolites by liquid chromatography-tandem mass spectrometry. SCH mimicked the disposition of TGZ/metabolites in vivo in rats and humans; TGZ was metabolized primarily to TS and to a lesser extent to TG and TQ. In human SCH, the biliary excretion index (BEI) was negligible for TGZ and TQ, ∼16% for TS, and ∼43% for TG over the incubation period; in rat SCH, the BEI for TS and TG was ∼13 and ∼41%, respectively. Hepatocyte accumulation of TS was extensive, with intracellular concentrations ranging from 132 to 222 μM in rat SCH; intracellular TGZ concentrations ranged from 7.22 to 47.7 μM. In human SCH, intracellular TS and TGZ concentrations ranged from 136 to 160 μM and from 49.4 to 84.7 μM, respectively. Pharmacokinetic modeling and Monte Carlo simulations were used to evaluate the impact of modulating the biliary excretion rate constant (Kbile) for TS on TS accumulation in hepatocytes and medium. Simulations demonstrated that intracellular concentrations of TS may increase up to 3.1- and 5.7-fold when biliary excretion of TS was decreased 2- and 10-fold, respectively. It is important to note that altered hepatobiliary transport and the extent of hepatocyte exposure may not always be evident based on medium concentrations (analogous to systemic exposure in vivo). Pharmacokinetic modeling/simulation with data from SCH is a useful approach to examine the impact of altered hepatobiliary transport on hepatocyte accumulation of drug/metabolites.
Footnotes
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This work was supported in part by the National Institutes of Health National Institute of General Medical Sciences [Grant GM41935] (to K.L.R.B); and the National Institutes of Health National Institute of Environmental Health Sciences [Grant T32-ES007126] (to T.L.M.).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.109.156653
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ABBREVIATIONS:
- TGZ
- troglitazone
- BSEP/Bsep
- bile salt export pump
- TS
- troglitazone sulfate
- AUCss
- area under the plasma concentration versus time curve at steady state
- AUC
- area under the plasma concentration versus time curve
- SCH
- sandwich-cultured hepatocyte(s)
- DEX
- dexamethasone
- HBSS
- Hanks' balanced salts solution
- MEM
- minimal essential medium
- DMEM
- Dulbecco's modified Eagle's medium
- TG
- troglitazone glucuronide
- TQ
- troglitazone quinone
- BEI
- biliary excretion index
- M
- medium
- C
- hepatocytes
- B
- bile.
- Received May 25, 2009.
- Accepted October 1, 2009.
- © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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