Importance of bicarbonate in bile salt independent fraction of bile flow

Am J Physiol. 1978 Aug;235(2):E158-64. doi: 10.1152/ajpendo.1978.235.2.E158.


The bile salt independent fraction (BSIF) of canalicular bile flow from the isolated rat liver perfused with bicarbonate-free perfusate is 50% of that from the liver perfused with bicarbonate-containing perfusate. HCO3-excretion is nearly eliminated and Na+ and Cl- excretion is reduced 50%. Replacement of HCO3- into perfusate increased bile flow by 0.3 microliter/g.min without changing bile acid excretion rate. 5.5-Dimethyl-2,4-oxazolidinedione (DMO) produced a similar effect. DMO was passively distributed between bile and plasma. The data indicate that a bicarbonate transport mechanism is responsible for production of up to 50% of the BSIF. Another weak acid, N-5[5-(2-methoxyethoxy)-2-pyrimidinyl]sulfamoylbenzene (glymidine), was rapidly excreted into bile and increased bile flow by over 2.0 microliter/g.min. Glymidine is probably excreted by an independent organic anion transport mechanism, and any effect on the bicarbonate transport mechanism is obscured. Canaliculus-enriched hepatocyte membrane fractions contained no HCO3-stimulated ATPase activity. Either this enzyme is unimportant in hepatocyte bicarbonate transport or transport occurs across membranes other than the bile canalicular membrane.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / metabolism*
  • Animals
  • Bicarbonates / metabolism*
  • Bile / metabolism*
  • Bile Acids and Salts / metabolism*
  • Bile Ducts, Intrahepatic / metabolism
  • Biological Transport, Active
  • In Vitro Techniques
  • Liver / anatomy & histology
  • Liver / metabolism
  • Male
  • Organ Size
  • Perfusion
  • Potassium / metabolism
  • Rats
  • Sodium / metabolism


  • Bicarbonates
  • Bile Acids and Salts
  • Sodium
  • Adenosine Triphosphatases
  • Potassium