Biliary excretion of estrone metabolites in the rat

We previously reported that sulfobromophthalein infusion inhibited the biliary excretion of estradiol glucuronides, whereas dibromosulfophthalein had no effect. In the present study, we examined the biliary excretion of estrone metabolites in rats. Biliary excretion of a tracer dose of intravenously injected [³H]estrone to control rats or EHBR and effects of the infusion of sulfobromophthalein and dibromosulfophthalein were studied. Biliary excretion of estrone metabolites was delayed in EHBR. Analysis of the biliary estrone metabolites revealed a marked decrease of the glucuronides in EHBR. Sulfobromophthalein and dibromosulfophthalein infusion (0.2 μmol/min/100 g b.wt.) inhibited the biliary excretion of estrone metabolites. However, the decrease in biliary excretion of the glucuronides was observed only with sulfobromophthalein that is excreted mainly as the glutathione conjugate. These findings indicate that glucuronides of estrone and its metabolites are partly excreted into bile by a canalicular organic anion carrier for sulfobromophthalein-glutathione, but not for dibromosulfophthalein.