title: Bile canalicular cationic dye secretion as a model for P-glycoprotein mediated transport.
abstract: This study explores properties of P-glycoprotein dependent membrane transport in rat liver with the use of acridine orange as the substrate. We studied the biliary secretion of the dye, its binding to canalicular membrane P-glycoprotein, and effects of the inhibitor cyclosporin A: acridine orange is excreted into bile together with less hydrophobic and glucuronidated metabolites. Cyclosporin A inhibited both the secretion of acridine orange and of its metabolites. In TR- animals, a rat strain that is deficient of the canalicular multi-specific organic anion transport system, non-metabolized acridine orange is the predominant species in bile and its secretion is also inhibited by cyclosporin A. Binding of acridine orange to liver P-glycoprotein was analyzed by photoaffinity labeling with azidopine, a substrate of P-glycoprotein dependent transport in multi-drug resistant tumor cells. Labeling of the immunoprecipitated P-glycoprotein was inhibited by acridine orange, verapamil, and by cyclosporin A. The results show that biliary secretion of acridine orange is highly analogous to P-glycoprotein mediated membrane drug transport in tumor cells that exhibit multi-drug resistance.
authors.affiliation: Department of General and Experimental Pathology, University of Vienna, University Hospital, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Thalhammer
authors.forename: V
authors.initials: V
authors.lastname: Stapf
authors.forename: L
authors.initials: L
authors.lastname: Gajdzik
authors.forename: J
authors.initials: J
authors.lastname: Graf
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000165:Acridine Orange / Q000493:pharmacokinetics*; D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000493:pharmacokinetics; D001648:Bile Canaliculi / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D004095:Dihydropyridines / Q000493:pharmacokinetics; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008954:Models, Biological; D010477:Perfusion; D011233:Precipitin Tests; D051381:Rats; D011919:Rats, Inbred Strains; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D001386:Azides; D002352:Carrier Proteins; D004095:Dihydropyridines; D008562:Membrane Glycoproteins; C041130:azidopine; D016572:Cyclosporine; D014700:Verapamil; D000165:Acridine Orange