Dmd047225 188..196

Inhibition of the bile salt export pump (BSEP) can cause intracellular accumulation of bile acids and is a risk factor for drug-induced liver injury in humans. Antiretroviral protease inhibitors lopinavir (LPV) and ritonavir (RTV) are reported BSEP inhibitors. However, the consequences of LPV and RTV, alone and combined (LPV/r), on hepatocyte viability, bile acid transport, and endogenous bile acid disposition in rat hepatocytes have not been examined. The effect of LPV, RTV, and LPV/r on cellular viability and the disposition of [H]taurocholic acid (TCA) and [C] chenodeoxycholic acid (CDCA) was determined in sandwichcultured rat hepatocytes (SCRH) and suspended rat hepatocytes. Lactate dehydrogenase and ATP assays revealed a concentrationdependent effect of LPV and RTV on cellular viability. LPV (5 mM), alone and combined with 5 mMRTV, significantly decreased [H]TCA accumulation in cells + bile of SCRHs compared with control. LPV/r significantly increased [H]TCA cellular accumulation (7.7 6 0.1 pmol/mg of protein) compared with vehicle and 5 mM LPV alone (5.1 6 0.7 and 5.0 6 0.5 pmol/mg of protein). The [H]TCA biliary clearance was reduced significantly by LPV and RTV and further reduced by LPV/r. LPV and RTV did not affect the initial uptake rates of [H]TCA or [C]CDCA in suspended rat hepatocytes. LPV (50 mM), RTV (5 mM), and LPV/r (5 and 50 mM/5 mM) significantly decreased the accumulation of total measured endogenous bile acids (TCA, glycocholic acid, taurochenodeoxycholic acid, glycochenodeoxycholic acid, and a/b-tauromuricholic acid) in SCRH. Quantification of endogenous bile acids in SCRH may reveal important adaptive responses associated with exposure to known