Objective: To investigate the mechanism of increase of serum bilirubin after hepatic ischemia-reperfusion.
Methods: 104 SD rats were randomly divided into 2 groups: Group A (sham operation group) and Group B (undergoing 70% hepatic 35 min ischemia-reperfusion). Then the rats were subdivided into subgroups according the different time points (1 and 6 hours, and 1, 3, 5 days after reperfusion). Bile of the ischemic hepatic lobes and blood from the vena cava were collected to examine the conjugated bilirubin (CB) in the bile and serum, and total bilirubin (TB) and alanine aminotransferase (ALT) in serum, and the bile generation rate was calculated. Tissues of the left liver lobe were collected to undergo microscopy with hematoxiline and eosin staining. Real time fluorescence PCR was used to analyze the mRNA expression of multi-drug resistance-associated protein 2 (MRP2) and radixin, a cytoskeleton crosslinker protein. Laser confocal method was used to analyze the localization of MRP2 and radixin in canalicular membrane.
Results: Pathological examination showed that there was only a mild inflammation in the liver tissues that had undergone ischemia-reperfusion, and no necrosis of hepatocytes was seen. 1 h approximately 3 d after reperfusion, the bile generation rate and CB level in bile were significant decreased, and the serum TB and CB levels were significantly increased 1 h approximately 5 d after reperfusion. Radixin expression was significantly reduced 6 h approximately 1 d after reperfusion, but down-regulation of MRP2 only occurred 6 h after reperfusion. Localization of MRP2 in the canalicular membrane was absent when the expression of radixin was missing.
Conclusion: Absence of MRP2 localization in canalicular membrane resulted from missing of radixin expression may be the mechanism of an increase of serum bilirubin after hepatic ischemia-reperfusion.