Qualitative differences in the hepatobiliary transport of sulfobromophthalein (BSP) and its glutathione conjugate (BSP-GSH).

The effect of phenobarbital pretreatment (PB; 75 mg/kg i.p. once daily for 5 days) and the simultaneous administration of taurocholate (TC; 200 mumol/kg i.v.), eosin(EO; 40-160 mumol/kg i.v.) and iodoxamic acid (IA; 125--500 mumol/kg i.v.) on the hepatic uptake and biliary excretion of BSP (30--120 mumol/kg i.v.) and BSP--GSH (40--160 mumol/kg i.v.) was investigated on diethyl maleate (DEM)-pretreated rats. The biliary excretion of BSP was not influenced by PB and EO, while it was increased by TC and decreased by IA. In contrast, the excretion of BSP--GSH was not influenced by TC or IA, it was stimulated by PB and inhibited by EO. In the different experimental conditions the hepatic uptake of BSP and BSP--GSH changed similarly: PB did not influence, TC, EO and IA decreased the accumulation of BSP and BSP--GSH in the liver. These results indicate that qualitative differences exist in the hepatobiliary transport of BSP and BSP--GSH, which manifest themselves following their hepatic uptake.