Substrate and phenobarbital induction of the biliary excretion of exogenous organic anions in rats.

Phenobarbital pretreatment significantly increased the biliary excretion of both non-metabolizable organic anions (rose bengal, eosin and amaranth) and the metabolizable bromsulphthalein (BSP). Phenobarbital stimulated the biliary excretion of BSP due to enhanced conjugation of BSP with glutathione and increased biliary excretion of bromsulphthalein-glutathione conjugate (BSP-GSH). On the other hand, pretreatment with the non-metabolizable substrates (rose bengal, eosin and amaranth) failed to stimulate the biliary excretion rate of these organic anions. Pretreatment with BSP enhanced the biliary excretion of total BSP due to a stimulation of GSH-S-transferase activity which conjugates BSP with glutathione.