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. Author manuscript; available in PMC: 2014 Feb 1.
Published in final edited form as: Drug Metab Rev. 2013 Feb;45(1):145–155. doi: 10.3109/03602532.2012.740048

Figure 3.

Figure 3

Enterohepatic circulation of bile acids. Bile acids are synthesized from cholesterol in hepatocytes. Bile acids are secreted into the gallbladder by BSEP and MRP2. Phospholipids are transported by MDR2, and cholesterol is transported by ABCG5/G8 transporters into bile. In the gallbladder, bile acids, phospholipids, and cholesterol form mixed micelles to solubilize cholesterol and reduce bile acid toxicity. After meal intake, the gallbladder releases bile into the small intestine, where bile acids facilitate the absorption of dietary lipids and vitamins. At the terminal ileum, most of the bile acids are reabsorbed by ASBT into the enterocytes and are secreted into the portal circulation by the basolateral bile acid transporters, Ostα/Ostβ. At the basolateral membrane of the hepatocytes, bile acids are taken up by the NTCP transporter for resecretion into the gallbladder, whereas Ostα/Ostβ and MRPs are responsible for basolateral bile acid efflux.