title: Disruption of the murine MRP (multidrug resistance protein) gene leads to increased sensitivity to etoposide (VP-16) and increased levels of glutathione.
abstract: The mrp (multidrug resistance protein) gene has been associated with the multidrug resistance of cancer cells in vitro and in vivo. To gain information on its physiological role, embryonic stem cells were used to generate mice homozygous for a disruption of the mrp gene, resulting in complete abrogation of mrp expression. No physiological abnormalities were observed, at least up to 4 months of age. Viability, fertility, and a range of histological, hematological, and serum-chemical parameters were similar in mrp(+/+) and mrp(-/-) mice. mrp(-/-) mice displayed an increased sensitivity to etoposide phosphate (2-fold) accompanied by greater bone marrow toxicity, whereas the acute toxicity of sodium arsenite was equivalent in mrp(+/+) and mrp(-/-) mice. Tissue levels of glutathione (GSH) were elevated in breast, lung, heart, kidney, muscle, colon, testes, bone marrow cells, blood mononuclear leukocytes, and blood erythrocytes of mrp(-/-) mice and were unchanged in organs known to express little if any mrp, such as the liver and small intestine. The increase in GSH was not due to an increase in the activity of gamma-glutamylcysteine synthetase, the rate-limiting enzyme for GSH synthesis. The findings demonstrate that mrp is dispensable for development and growth but exerts a role in drug detoxification and GSH metabolism.
authors.affiliation: Department of Pharmacology, Cancer Center, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lorico
authors.forename: G
authors.initials: G
authors.lastname: Rappa
authors.forename: R A
authors.initials: RA
authors.lastname: Finch
authors.forename: D
authors.initials: D
authors.lastname: Yang
authors.forename: R A
authors.initials: RA
authors.lastname: Flavell
authors.forename: A C
authors.initials: AC
authors.lastname: Sartorelli
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D018053:Arsenites / Q000633:toxicity; D001853:Bone Marrow / Q000473:pathology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005047:Etoposide / Q000031:analogs & derivatives* / Q000633:toxicity*; D005260:Female; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009928:Organ Specificity; D009943:Organophosphorus Compounds / Q000633:toxicity*; D017670:Sodium Compounds / Q000633:toxicity; D013234:Stem Cells
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D018053:Arsenites; D005047:Etoposide; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009943:Organophosphorus Compounds; D017670:Sodium Compounds; C017947:sodium arsenite; C061400:etoposide phosphate