Bile acids and their salts have essential functions in the liver and small intestine. Synthesis of bile acids in the liver provides a major catabolic pathway for cholesterol. In the intestine, bile salts aid in the emulsification of lipids and solubilization of essential nutrients and vitamins. The secretion of bile normally depends on the function of membrane transporters in the hepatocytes and cholangiocytes. The coordinated action of these transporters is crucial to hepatic drug clearance, biliary secretion of cholephilic compounds and xenobiotics...