Abstract
Multidrug resistance P-glycoprotein 2 (Mdr2) is a phospholipid translocator in the canalicular membrane that is essential for the formation of biliary phospholipid vesicles and mixed lipid/bile salt micelles. Incorporation into biliary vesicles and micelles is thought to contribute to the hepatobiliary excretion of certain hydrophobic organic anions, such as indocyanine green (ICG). The present studies characterized the biliary excretion of two hydrophobic organic anions, ICG and estradiol-17β(β-d-glucuronide) (E217G), in the single-pass isolated perfused liver and the biliary excretion of glutathione (GSH) in vivo in wild-type andMdr2−/− female mice. The biliary excretion of ICG (0.4 μmol) was reduced by 90%, while the biliary excretion of total GSH was decreased by 65% in Mdr2−/−mice relative to wild-type mice. In contrast, the biliary excretion of E217G (0.1 μmol) was increased by 30% inMdr2−/− mice. These data indicate that the absence of Mdr2 differentially influences the biliary excretion of these organic anions and suggest that phospholipid vesicles and mixed micelles in bile are essential for the biliary excretion of ICG.
Footnotes
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Send reprint requests to: Dr. Mary Vore, 306 HSRB Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40536. E-mail: maryv{at}pop.uky.edu
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This work was supported by the Public Health Service Grant GM-55343.
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↵2 Human genes and their products are capitalized, whereas rodent genes and their products are lowercase with first letter capitalized.
- Abbreviations used are::
- MDR
- multidrug resistance genes
- MRP
- multidrug resistance-associated protein genes
- MRP2
- canalicular isoform of MRP
- MDR1
- multidrug resistance P-glycoprotein 1
- MDR3/Mdr2
- multidrug resistance P-glycoprotein 2
- E217G
- estradiol-17β(β-d-glucuronide)
- E23SO417G
- estradiol-3-sulfate-17β(β-d-glucuronide)
- GSH
- glutathione
- ICG
- indocyanine green
- Received September 12, 2000.
- Accepted January 15, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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