Figure 2: Model of proposed routes for transhepatic flux of different types of bile acids: Conjugated hydrophilic BAs seem to take the “fast transit” (green) route through the hepatocyte without “touching” FXR to a larger extent whereas unconjugated, hydrophobic BAs tend to take a route which involves binding to L-FABP and transfer to the perinuclear ER membrane from where they are delivered to FXR (orange route). Abbreviations: OATPs (= organic anion transport polypeptides), NTCP (= sodium-dependent bile acid cotransporting polypeptide), L-FABP (=liver-specific bile acid binding protein), mEH (=microsomal epoxide hydrolase), GSTs (= Glutathione-S-transferases), 3α-HSD (= 3-alpha hydroxysteroid dehydrogenase), BSEP (=bile salt export pump), BACS (=bile acyl-CoA synthetase), BAAT (bile-acyl-CoA: amino acid N-Acyltransferase).