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 o xidized glutathione (GSSG) values and reduced glutathione (GSSG/GSH) r atio in the bile increased dose-dependently and then returned to contr ol level within 10 min, whereas the hepatic ATP level and bile dow rat e were not affected by t-BuOOH at doses of up to 1.0 mmol/kg. These da ta 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 appreci ably during ischemia for 10 or 30 min or during subsequent reperfusion , but the GSSG/GSH ratio increased after ischemia for 30 min, The rate of bile flow and the biliary level of GSH decreased after ischemia fo r 30 min in proportion to the decrease in the hepatic ATP level. Howev er, the biliary GSSG concentration did not vary on reperfusion, althou gh GSSG secretion into the bile is also related to the hepatic ATP lev el. As a result, the GSSG/GSH ratio in the bile increased during reper fusion after ischemia for 30 min. This increased ratio is thought to r eflect oxidation of hepatic GSH by hydroperoxide produced during reper fusion. The GSSG/GSH ratio in the bile after 30 min ischemia correspon ded to that observed after a small dose (0.07 mmole/kg body wt) of t-B uOOH, which hepatocytes could dismute rapidly without loss of their vi ability. Furthermore, the redox state of NADP (NADPH/[NADPH + NADP(+)] ) remained constant during ischemia-reperfusion. These findings sugges t that reactive oxygen was produced in the liver during the reperfusio n after 30 min ischemia in amounts small enough to be scavenged by int rinsic protection mechanisms, including the NADP-glutathione system. ( C) 1994 Academic Press, Inc.