The biliary HCO3- umbrella: experimental evidence revisited

Purpose of review To critically review most recent experimental evidence for the protective action of biliary HCO3- secretion against bile acid-induced bile duct damage and development of fibrosing cholangiopathy in humans and experimental animals. Recent findings Studies in human cholangiocytes in vitro indicate that a biliary HCO3- umbrella protects against bile acid-induced cholangiocyte damage and apoptosis in humans. The Cl-/HCO3- exchanger, AE2, and an intact biliary glycocalyx appear crucial for its stability. Related studies with experimental animal models in vivo have to be interpreted with caution as humans and mice differ not only with regard to bile salt pool, but also their expression patterns of transport proteins and signalling molecules. Summary Adequate biliary HCO3- secretion may protect against bile salt-induced cholangiopathies. Future therapeutic strategies in biliary diseases will aim at stabilizing the biliary HCO3- umbrella.