Relation between glutathione redox changes and biliary excretion of taurocholate in perfused rat liver

The influence of the intracellular glutathione status on bile acid excretion was studied in the perfused rat liver. Perturbation of the thiol redox state by short term additions of diamide (100 microM) or hydrogen peroxide (250 microM) or t-butyl hydroperoxide (250 microM) led to a reversible inhibition of biliary taurocholate release without affecting hepatic uptake; inhibition amounted to 45% for diamide and 90% for the hydroperoxides. Concomitantly, the bile acid accumulated intracellularly. Bile flow increased from 1.3 to 2.0 microliters X min-1 X g liver-1 upon infusion of taurocholate (10 microM); the latter value was suppressed to 1.2 microliters X min-1 X g liver-1 by the addition of t-butyl hydroperoxide (250 microM). Similarly, the hepatic disposition of another bile constituent, bilirubin, was suppressed by 70% upon addition of hydrogen peroxide. While the addition of hydrogen peroxide inhibited also the endogenous release of bile acids almost completely, endogenous bile flow was much less affected, decreasing from 1.3 to 1.0 microliters X min-1 X g liver-1. Measurement of [14C]erythritol clearance showed bile/perfusate ratios of about unity both in the absence and presence of hydrogen peroxide, suggesting canalicular origin of the bile under both conditions. In livers from Se-deficient rats low in Se-GSH peroxidase (less than 5% of controls), hydrogen peroxide inhibited taurocholate transport substantially less, providing evidence for the involvement of glutathione in mediating the inhibition observed in normal livers. The percentage inhibition of taurocholate release and intracellular glutathione disulfide (GSSG) content were closely correlated. The addition of t-butyl hydroperoxide caused a several-fold increase of biliary GSSG release, whereas biliary GSH release was even decreased. The results establish a role of glutathione in canalicular taurocholate disposition.