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Updated: Jul 6, 2026
Creation of Reversible Cholestatic Rat Model
Published on: May 21, 2011
The rat canalicular conjugate export pump (Mrp2) is down-regulated in intrahepatic and obstructive cholestasis
M Trauner1, M Arrese, C J Soroka
1Liver Center and Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8019, USA.
Background & Aims:
The excretion of various organic anions into bile is mediated by an adenosine triphosphate-dependent conjugate export pump, which has been identified as the canalicular isoform of the multidrug resistance protein (Mrp2). Mrp2 function is impaired in various experimental models of intrahepatic and obstructive cholestasis, but the underlying molecular mechanisms are unclear. The aim of this study was to investigate these molecular mechanisms.
Methods:
The effects of endotoxin, ethinylestradiol, and common bile duct ligation (CBDL) on Mrp2 protein, messenger RNA (mRNA) expression, and Mrp2 tissue localization were determined in rat livers by Northern blotting, Western analysis, and tissue immunofluorescence. To assess whether changes were specific for Mrp2, we also examined the expression of canalicular ecto-adenosine triphosphatase (ecto-ATPase) and mdr P-glycoproteins (P-gp).
Results:
All three cholestatic models resulted in a marked decrease in Mrp2 protein (P < 0.01) and its tissue localization at the canalicular membrane. Mrp2 mRNA levels diminished profoundly after endotoxin (P < 0.0005) and CBDL (P < 0.05), but did not change after ethinylestradiol. In contrast to Mrp2, protein expression of ecto-ATPase and P-gp remained unchanged in endotoxin- and ethinylestradiol-treated animals, whereas P-gp levels increased after CBDL (P < 0.05).
Conclusions:
Down-regulation of Mrp2 expression may explain impaired biliary excretion of amphiphilic anionic conjugates in these models of cholestasis.
Insights
Cholestasis impairs bile excretion by reducing multidrug resistance-associated protein 2 (Mrp2). This study investigated the molecular mechanisms behind Mrp2 down-regulation in experimental cholestasis models.
Area of Science:
- Hepatology
- Molecular Biology
- Drug Transport
Background:
- Bile excretion of organic anions relies on the Mrp2 export pump.
- Mrp2 function is compromised in cholestasis, but mechanisms are unknown.
Purpose of the Study:
- Investigate molecular mechanisms of Mrp2 impairment in cholestasis.
- Determine Mrp2 protein, mRNA, and localization changes in response to cholestatic stimuli.
Main Methods:
- Used endotoxin, ethinylestradiol, and bile duct ligation in rat models.
- Assessed Mrp2 expression via Western blot, Northern blot, and immunofluorescence.
- Examined canalicular ecto-ATPase and P-glycoprotein expression for specificity.
Main Results:
- All models significantly decreased Mrp2 protein and canalicular localization.
- Endotoxin and CBDL reduced Mrp2 mRNA; ethinylestradiol did not.
- Ecto-ATPase and P-gp levels were largely unaffected, except for increased P-gp after CBDL.
Conclusions:
- Down-regulation of Mrp2 expression contributes to impaired biliary excretion in cholestasis.
- These findings clarify molecular mechanisms underlying cholestasis-induced Mrp2 dysfunction.
