The rat canalicular conjugate export pump (Mrp2) is down-regulated in intrahepatic and obstructive cholestasis.

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Trauner M, Arrese M, Soroka CJ, Ananthanarayanan M, Koeppel TA, Schlosser SF, Suchy FJ, Keppler D, Boyer JL

The rat canalicular conjugate export pump (Mrp2) is down-regulated in intrahepatic and obstructive cholestasis.

Gastroenterology. 1997 Jul;113(1):255-64.

PubMed ID

9207286 [ View in PubMed

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Abstract

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.

DrugBank Data that Cites this Article

Drug Transporters

Drug	Transporter	Kind	Organism	Pharmacological Action	Actions
Ethinylestradiol	Canalicular multispecific organic anion transporter 1	Protein	Humans	Unknown	Inhibitor Inducer	Details