Regulation of gene expression by different bile acids in primary hepatocytes. Hepatocytes were isolated from the livers of wild-type and FXR^–/– male mice and treated with the indicated concentrations of taurine-conjugated bile acids or the FXR-specific agonist GW4064 for 16 hours. Total RNA was isolated from the cells, and the levels of SHP and BSEP mRNA were quantitated by real-time RT-PCR. The numbers shown are the averages from three experiments and triplicate determinations for each mRNA. Error bars indicate SEM. TCA, taurocholic acid (circles); TCDCA, taurochenodeoxycholic acid (symbol X); TβMCA, tauro-β-muricholic acid (squares); GW4064, 3-(2,6-dichlorophenyl)-4-(3′-carboxy-2-chloro-stilben-4-yl)-oxymethyl-5-isopropyl-isoxazole (48) (triangles).