Output of liver fatty acid-binding protein (L-FABP) in bile

Liver fatty acid-binding protein (L-FABP) is a small cytoplasmic molecule highly expressed in the liver. Since L-FABP exhibits affinities for several biliary components, its presence in bile was explored by Western blotting and competitive ELISA in various mammalian species. A L-FABP-like immunoreactivity was consistently found in both hepatic and gallbladder bile. A close molecular identity between this 14 kDa biliary protein and the purified L-FABP was assessed by immunological analyses and high performance capillary electrophoresis. Pharmacological induction of hepatic L-FABP biosynthesis led to a similar increase in biliary L-FABP levels showing a close relationships between the cytosolic and biliary contents of this protein. Finally, a correlation between the presence of L-FABP in bile and both bile flow and bile acid release was found. These data suggest an output of L-FABP in bile in normal conditions which might be coupled with the physiological release of biliary components.