title: The ABCG2 efflux transporter from rabbit placenta: Cloning and functional characterization.
abstract: In human placenta, the ATP-binding cassette efflux transporter ABCG2 is highly expressed in syncytiotrophoblast cells and mediates cellular excretion of various drugs and toxins. Hence, physiological ABCG2 activity substantially contributes to the fetoprotective placenta barrier function during gestation. Developmental toxicity studies are often performed in rabbit. However, despite its toxicological relevance, there is no data so far on functional ABCG2 expression in this species. Therefore, we cloned ABCG2 from placenta tissues of chinchilla rabbit. Sequencing showed 84-86% amino acid sequence identity to the orthologues from man, rat and mouse. We transduced the rabbit ABCG2 clone (rbABCG2) in MDCKII cells and stable rbABCG2 gene and protein expression was shown by RT-PCR and Western blot analysis. The rbABCG2 efflux activity was demonstrated with the Hoechst H33342 assay using the specific ABCG2 inhibitor Ko143. We further tested the effect of established human ABCG2 (hABCG2) drug substrates including the antibiotic danofloxacin or the histamine H2-receptor antagonist cimetidine on H33342 accumulation in MDCKII-rbABCG2 or -hABCG2 cells. Human therapeutic plasma concentrations of all tested drugs caused a comparable competitive inhibition of H33342 excretion in both ABCG2 clones. Altogether, we first showed functional expression of the ABCG2 efflux transporter in rabbit placenta. Moreover, our data suggest a similar drug substrate spectrum of the rabbit and the human ABCG2 efflux transporter.
authors.affiliation: Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, Universität Leipzig, An den Tierkliniken 15, D-04103 Leipzig, Germany. Electronic address: halwachs@vetmed.uni-leipzig.de.
authors.forename: Sandra
authors.initials: S
authors.lastname: Halwachs
authors.affiliation: Federal Institute for Risk Assessment (BfR), Pesticide Safety, Max-Dohrn-Straße 8-10, D-10589 Berlin, Germany. Electronic address: Carsten.Kneuer@bfr.bund.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Kneuer
authors.affiliation: Federal Institute for Risk Assessment (BfR), Pesticide Safety, Max-Dohrn-Straße 8-10, D-10589 Berlin, Germany. Electronic address: gohlsch.katrin@gmx.de.
authors.forename: Katrin
authors.initials: K
authors.lastname: Gohlsch
authors.affiliation: Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, Universität Leipzig, An den Tierkliniken 15, D-04103 Leipzig, Germany. Electronic address: loki.mm21@web.de.
authors.forename: Marian
authors.initials: M
authors.lastname: Müller
authors.affiliation: Federal Institute for Risk Assessment (BfR), Pesticide Safety, Max-Dohrn-Straße 8-10, D-10589 Berlin, Germany. Electronic address: Vera.Ritz@bfr.bund.de.
authors.forename: Vera
authors.initials: V
authors.lastname: Ritz
authors.affiliation: Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, Universität Leipzig, An den Tierkliniken 15, D-04103 Leipzig, Germany. Electronic address: honscha@vetmed.uni-leipzig.de.
authors.forename: Walther
authors.initials: W
authors.lastname: Honscha
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2 / Q000235:genetics* / Q000502:physiology*; D000818:Animals; D003001:Cloning, Molecular; D004285:Dogs; D005260:Female; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D008297:Male; D051379:Mice; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011817:Rabbits / Q000235:genetics* / Q000378:metabolism; D051381:Rats
chemical_list: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2
keywords: ABCG2/BCRP efflux transporter; Active drug transport; MDCKII in vitro model; Placenta barrier; Rabbit; developmental toxicity testing