[Physiology of bile secretion].

Canalicular bile secreted by the hepatocyte consists of at least two fractions: one is initiated by active transport of bile acids, the other is due to active transport of inorganic ions. Bilirubin and other organic anions, organic cations, and neutral compounds are secreted into the canalicular bile as well as lecithin and cholesterol. Subsequently the biliary tree, the gallbladder, and the enterohepatic circulation of bile acids have an effect on bile formation. Choleresis induced by drugs may be due to a direct osmotic effect of the compound secreted in bile or to an increase of the bile acid independent fraction of bile flow. Cholestasis frequently is caused by inhibition of the bile acid independent fraction. Studies on micellar solubility of cholesterol have led to new concepts concerning formation of cholesterol gallstones and their dissolution with chenodeoxycholic-acid therapy.