Vesicle- and Hepatocyte-Based Assays for Identification of Drug Candidates Inhibiting BSEP Function.

Transporters play a crucial role in the uptake of endo- and exogenous molecules in hepatocytes and efflux into the bile. The bile salt export pump (BSEP; ABCB11) is of major importance for efflux of bile salts to the bile and BSEP inhibition frequently provokes drug-induced cholestasis. This chapter describes two assays to determine inhibition of BSEP-mediated bile salt excretion. The first assay uses inside-out membrane vesicles, prepared from BSEP-transfected cell lines. The cholestasis potential of compounds can be determined by specifically investigating the ability to inhibit BSEP-mediated uptake of tauro-nor-THCA-24-DBD, a fluorescent bile salt derivative. For the second assay, relative accumulation of tauro-nor-THCA-24-DBD in sandwich-cultured hepatocytes, which represents a more biorelevant in vitro system, is investigated. Through incubation with standard or Ca