Effect of pretreatment with exogenous organic anions on biliary excretion in rats

The effect of pretreatment with exogenous organic anions (rose bengal, amaranth, eosine, bromsulphthalein) on biliary excretion has been investigated in rats. Pretreatment with exogenous nonmetabolized organic anions (rose bengal, amaranth, eosine) had no significant influence on the biliary excretion of rose bengal, amaranth, eosine, bromsulphthalein and bromsulphthalein-glutathione conjugate. Pretreatment with bromsulphthalein, which is metabolized in the liver, significantly enhanced the biliary excretion of total bromsulphthalein due to stimulation of the conjugation of BSP with glutathione. Both the activity of glutathione S-transferase and the glutathione content in the liver were increased following BSP pretreatment. Pretreatment with rose bengal and eosine influenced neither the conjugation of bromsulphthalein with glutathione, nor the biliary excretion of total bromsulphthalein. These results indicate that the biliary excretion rate of exogenous organic anions cannot be increased by pretreatment with substrates of the hepatic transport system. The enhanced biliary output of total bromsulphthalein after bromsulphthalein pretreatment can be explained solely by stimulation of its conjugation with glutathione.