Changes in Biliary Glutathione Level during Ischemia-Reperfusion of Rat Liver

Changes in hepatic and biliary glutathione levels were studied in rat liver treated with tert-butyl hydroperoxide (t-BuOOH) and subjected to ischemia-reperfusion. Immediately after t-BuOOH administration, the oxidized glutathione (GSSG) values and reduced glutathione (GSSG/GSH) ratio in the bile increased dose-dependently and then returned to control level within 10 min, whereas the hepatic ATP level and bile flow rate were not affected by t -BuOOH at doses of up to 1.0 mmol/kg. These data suggested that the liver remains viable on treatment with up to 1.0 mmole/kg t-BuOOH, and that hepatocytes can rapidly dismute t-BuOOH at up to this dose. The hepatic GSH and GSSG levels did not vary appreciably during isehemia for 10 or 30 min or during subsequent reperfusion, but the GSSG/GSH ratio increased after isehemia for 30 min. The rate of bile flow and the biliary level of GSH decreased after isehemia for 30 min in proportion to the decrease in the hepatic ATP level. However, the biliary GSSG concentration did not vary on reperfusion, although GSSG secretion into the bile is also related to the hepatic ATP level. As a result, the GSSG/GSH ratio in the bile increased during reperfusion after ischemia for 30 min. This increased ratio is thought to reflect oxidation of hepatic GSH by hydroperoxide produced during reperfusion. The GSSG/GSH ratio in the bile after 30 min ischemia corresponded to that observed after a small dose (0.07 mmole/kg body wt) of t-BuOOH, which hepatocytes could dismute rapidly without loss of their viability. Furthermore, the redox state of NADP (NADPH/[NADPH + NADP+]) remained constant during ischemia-reperfusion. These findings suggest that reactive oxygen was produced in the liver during the reperfusion after 30 min ischemia in amounts small enough to be scavenged by intrinsic protection mechanisms, including the NADP-glutathione system.