title: Rifampicin and verapamil induce the expression of P-glycoprotein in vivo in Ehrlich ascites tumor cells.
abstract: The effect of an in vivo treatment with two commonly employed drugs that are P-glycoprotein substrates, verapamil and rifampicin, on Ehrlich ascites carcinoma cells, was evaluated. Ehrlich ascites carcinoma cells were inoculated i.p. in CD-1 mice and animals were orally treated for 10 days with rifampicin (60 mg/kg/day) or verapamil (6 mg/kg/day). In the harvested cells the transcripts for mdr1a and mrp1, but not those for mdr1b, mrp2 and CYP3A, were detected, and treatment with verapamil or rifampicin did not modify the levels of the transcripts. On the contrary, an increased expression of P-glycoprotein was observed at the protein level with Western blot. The intracellular uptake of doxorubicin, a P-glycoprotein and MRP substrate, was significantly lower in cells obtained from treated animals in comparison with cells obtained from controls; in addition, the uptake was increased by a pretreatment with verapamil. The survival time of control animals implanted with untreated cells was similar to that of animals inoculated with cells obtained from rifampicin treated animals, however, the antineoplastic effect of doxorubicin was significanly higher in control animals. A treatment with rifampicin or verapamil in Ehrlich ascites tumor confers resistance to the antineoplastic drug doxorubicin, probably through an increased expression of P-glycoprotein.
authors.affiliation: Department of Biomedical Sciences, University of Trieste, Via Giorgieri 7, Trieste I-34127, Italy.
authors.forename: Marilena
authors.initials: M
authors.lastname: Granzotto
authors.forename: Ilenia
authors.initials: I
authors.lastname: Drigo
authors.forename: Luigi
authors.initials: L
authors.lastname: Candussio
authors.forename: Anna
authors.initials: A
authors.lastname: Rosati
authors.forename: Fiora
authors.initials: F
authors.lastname: Bartoli
authors.forename: Tullio
authors.initials: T
authors.lastname: Giraldi
authors.forename: Giuliana
authors.initials: G
authors.lastname: Decorti
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000187:drug effects*; D000818:Animals; D000970:Antineoplastic Agents; D015153:Blotting, Western; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002286:Carcinoma, Ehrlich Tumor / Q000188:drug therapy / Q000378:metabolism; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012293:Rifampin / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D004317:Doxorubicin; D014700:Verapamil; D012293:Rifampin