title: Importance of bicarbonate in bile salt independent fraction of bile flow.
abstract: 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.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001646:Bile / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism*; D001653:Bile Ducts, Intrahepatic / Q000378:metabolism; D001693:Biological Transport, Active; D066298:In Vitro Techniques; D008099:Liver / Q000033:anatomy & histology / Q000378:metabolism; D008297:Male; D009929:Organ Size; D010477:Perfusion; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D001647:Bile Acids and Salts; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium