Hepatic transport of sulphobromphthalein and sulphobromphthalein-glutathione conjugate in control and phenobarbital-pretreated rats.

The biliary excretion of intravenously administered sulphobromphthalein (BSP) and sulphobromphthalein-glutathione conjugate (BSP-GSH) has been studied in control and phenobarbital-pretreated rats (75 mg/kg intraperitoneally daily for five days). Hepatic utake and biliary excretion of free BSP have been investigated in rats pretreated with diethyl maleate (DEM), which depletes the liver of glutathione (GSH) and therefore inhibits the conjugation of BSP with GSH. Phenobarbital pretreatment caused no significant change in the hepatic uptake of BSP or BSP-GSH. The conjugation of BSP and GSH in phenobarbital-preatreated rats was significantly faster than in the controls. The biliary excretion of free BSP was unchanged after phenobarbital induction, but significantly more BSP-GSH was excreted than in the controls. Thus, both the faster conjugation and the enhanced transport of BSP-GSH into the bile canaliculi were responsible for the increased biliary excretion of BSP in phenobarbital pretreated rats.