title: Specificity of doxorubicin versus rhodamine-123 in assessing P-glycoprotein functionality in the LLC-PK1, LLC-PK1:MDR1 and Caco-2 cell lines.
abstract: The LLC-PK1:MDR1, LLC-PK1 and Caco-2 cell lines were used to investigate whether rhodamine-123 or doxorubicin would be the preferred substrate to study P-glycoprotein (P-gp) functionality in vitro. Both rhodamine-123 and doxorubicin showed highly polarised transport in the Caco-2 cell line and the LLC-PK1:MDR1 cell line, indicating that P-gp is actively transporting these drugs. However, for rhodamine-123 polarised transport was also seen in the monolayers of the wild-type LLC-PK1 cell line, indicating the presence of another active transporter for this compound. Polarised transport of doxorubicin in the Caco-2 and the LLC-PK1:MDR1 cell lines could be inhibited by the P-gp inhibitors SDZ-PSC 833 (PSC 833), cyclosporin A (CsA), verapamil and quinine, but not by the inhibitors for the organic cation carrier systems cimetidine and tetraethylammonium (TEA). Polarised transport of rhodamine-123 in the Caco-2 cell line could only be inhibited by P-gp inhibitors. In the LLC-PK1:MDR1 and LLC-PK1 cell lines transport was also inhibited by inhibitors for the organic cation transport systems. In conclusion, rhodamine-123 is a substrate for both P-gp and the organic cation carrier systems in the kidney cell line. This indicates that rhodamine-123 is not selective enough to study P-gp functionality in cell systems were organic cation carrier systems are also present. Doxorubicin appears to be a more selective P-gp substrate and therefore more useful in studying P-gp functionality in vitro.
authors.affiliation: Leiden/Amsterdam Center for Drug Research, Division of Pharmacology, Leiden University, PO Box 9503, 2300 RA, Leiden, The Netherlands. i.sandt@lacdr.leidenuniv.nl
authors.forename: I C
authors.initials: IC
authors.lastname: van der Sandt
authors.forename: M C
authors.initials: MC
authors.lastname: Blom-Roosemalen
authors.forename: A G
authors.initials: AG
authors.lastname: de Boer
authors.forename: D D
authors.initials: DD
authors.lastname: Breimer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002460:Cell Line; D016764:Cell Polarity; D002927:Cimetidine / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004317:Doxorubicin / Q000493:pharmacokinetics*; D018432:Drug Resistance, Multiple / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology; D006801:Humans; D007700:Kinetics; D018374:LLC-PK1 Cells; D020112:Rhodamine 123 / Q000493:pharmacokinetics*; D013552:Swine; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D020112:Rhodamine 123; D002927:Cimetidine; D004317:Doxorubicin; D016572:Cyclosporine; D014700:Verapamil