OBJECTIVETo investigate the mechanism of plasma bilirubin level increase after hepatic ischemia-reperfusion in rats.

METHODSRats were divided into a sham operation group (A group), a 20 min ischemia-reperfusion group (B group) and a 35 min ischemia-reperfusion group (C group). Study time points were 6 hours and 1, 3, and 5 days after the reperfusion. Pathological changes in the livers were studied with histological slides stained with hematoxilin and eosin. Routine biochemistry methods were used to detect the bilirubin level of blood plasma and the bile drained from the ischemic hepatic lobes. RT-PCR was used to analyze the expression of the multidrug resistance-associated protein 2 (MRP2) and mRNA. Immunohistochemistry was used to analyze the localization of MRP2 in the canalicular membrane.

RESULTSB and C groups showed a mild inflammatory reaction without hepatocyte necrosis. At 6 h and 1 day after reperfusion, there was a significant increase of the plasma bilirubin level and a decrease of the bilirubin level of the drained bile in B group. These changes lasted to the day 3 and day 5 in C group. MRP2 mRNA down-regulation was found at 6 h only in the B and C groups. No localization of MRP2 in the canalicular membrane was found but it appeared in "esicules" under the canalicular membrane in C group.

CONCLUSIONSAbsence of MRP2 localization in the canalicular membrane could be the cause of the blood plasma bilirubin level increase after liver ischemia-reperfusion.