title: Xenopus laevis oocytes expressing human P-glycoprotein: probing trans- and cis-inhibitory effects on [3H]vinblastine and [3H]digoxin efflux.
abstract: P-glycoprotein (P-gp; MDR1) recognizes and actively transports many structurally diverse compounds (hydrophobic neutral and cationic). We studied MDR1-mediated drug transport using a high-throughput (96-well) oocyte expression system. MDR1-expressing oocytes contained sufficient ATP levels to conduct fundamental efflux studies; the optimal experimental temperature was 25 degrees C. [(3)H]Vinblastine efflux by MDR1-expressing oocytes was detectable and afforded a K(m) of 145.5+/-25.4microM. [(3)H]Vinblastine (5.6+/-0.3microM) and [(3)H]digoxin (1.0+/-0.1microM) were individually injected into MDR1-expressing oocytes and their efflux monitored. Quinidine and verapamil, known MDR1 substrates/inhibitors, showed trans-inhibition on MDR1-mediated [(3)H]vinblastine and [(3)H]digoxin efflux. Conversely, doxorubicin demonstrated cis-inhibition without trans-inhibition on MDR1-mediated [(3)H]vinblastine efflux. The MDR1-expressing oocyte system offers researchers with an alternative in vitro method to screen compounds and may allow one to probe P-gp drug-drug and/or drug-inhibitor interactions.
authors.affiliation: Kobuchisawa Research Laboratories, Fuji Biomedix Co., Ltd., Hokuto-shi, Yamanashi, Japan.
authors.forename: Promsuk
authors.initials: P
authors.lastname: Jutabha
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wempe
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Jun
authors.initials: J
authors.lastname: Otomo
authors.forename: Toshihito
authors.initials: T
authors.lastname: Kadota
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endou
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D004077:Digoxin / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D057166:High-Throughput Screening Assays; D006801:Humans; D007700:Kinetics; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011802:Quinidine / Q000378:metabolism / Q000494:pharmacology*; D013696:Temperature; D014700:Verapamil / Q000378:metabolism / Q000494:pharmacology*; D014747:Vinblastine / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D014747:Vinblastine; D004077:Digoxin; D004317:Doxorubicin; D000255:Adenosine Triphosphate; D014700:Verapamil; D011802:Quinidine