Effect of cholestyramine-induced bile acid depletion on the hepatobiliary transport of cholephilic organic anions in rats.

Four hours after oral administration of cholestyramine (1.0 g/kg) the biliary output of bile acids decreased to 21 per cent of the control value. The biliary excretion of indocyanine green (ICG; 15--60 mumol/kg i.v.), rose bengal (RB; 15--60 mumol/kg i.v.), bromsulphthalein (BSP; 15--60 mumol/kg i.v.), bromcresol green (BCG;15--60 mumol/kg i.v.) and eosine (EO; 30--120 mumol/kg i.v.) was considerably depressed by cholestyramine pretreatment. The extent and duration of the reduction in the biliary excretion of organic anions in response to bile acid depletion were found to increase with their doses. In contrast, the biliary excretion rates of bromsulphthalein-glutathione conjugate (BSP-GSH; 60--240 mumol/kg i.v.) and amaranth (AM; 60--240 mumol/kg i.v.) remained unchanged following bile acid depletion. The hepatic uptake of the cholephilic agents investigated was not affected by bile acid depletion. It is concluded that the biliary excretion rates of ICG, RB, BSP, BCG and EO are dependent on the excretion rates of endogenous bile acids. The hepatic transport rates of BSP-GSH and AM, however, seem to be relatively insensitive to the biliary output of endogenous bile salts.