Biliary Secretion of Glutathione in Estradiol 17 (cid:1) - D -Glucuronide-Induced Cholestasis

Estradiol-17 (cid:1) - D -glucuronide (E2-17G) induces an acute but reversible inhibition of bile flow after its intravenous administra- tion to rats, due in part to the endocytic retrieval of the canalicular multidrug resistance-associated transporter protein 2 and the bile salt export pump, transporters that contribute to bile flow. Decreased bile salt-independent bile flow (BSIF) is also involved and persists during the phase of recovery from cholestasis. Because glutathione and HCO 3 (cid:1) are major contrib-utors to BSIF, we evaluated changes in their biliary excretion and the hepatic content of total glutathione during E2-17G-induced cholestasis. E2-17G acutely decreased bile flow and biliary excretion of total glutathione by about 80%; glutathione excretion was still inhibited at 80 min and 120 min, even though bile flow was partially and totally restored, respectively. Neither liver glutathione content nor the proportions of oxidized gluta- thione in bile and liver were affected by E2-17G at any time. concentrations in bile were unchanged, so that secretion paralleled variations in bile flow. In the isolated perfused liver, addition of E2-17G decreased both bile flow and the biliary concentration of glutathione, whereas addition of its nonchole- static isomer estradiol-3- D -glucuronide (E2-3G) did not inhibit bile flow, but significantly reduced the concentration of gluta- thione in bile. The bile:liver concentration ratios of glutathione were significantly decreased in vivo by E2-17G and in the perfused liver by E2-17G and E2-3G. These data indicate that E2-17G cis- inhibits the canalicular transport of glutathione and thus contributes to the cholestatic effect by inhibiting BSIF. E2-17G and did not recover in parallel with either bile flow or the biliary excretion of a classic Mrp2 substrate, dinitrophenyl- S -glutathione (DNP-SG). In the current study, we therefore evaluated the biliary excretion and hepatic content of total glutathione in E2-17G-induced cholestasis in vivo and in the isolated perfused rat liver. We also examined the bile secretory rate of HCO 3 (cid:1) and the potential interference of bilirubin conjugates with glutathione secretion into bile. The data show that E2-17G severely impaired the biliary secretion of both GSH and GSSG in vivo and in the perfused liver without influencing their liver content, thus indicating selective inhibition of canalicular transport of these glutathione species.