title: Heterologous expression of various P-glycoproteins in polarized epithelial cells induces directional transport of small (type 1) and bulky (type 2) cationic drugs.
abstract: We recently showed that absence of mdr1-type P-glycoprotein (P-gp) in mice resulted in profoundly reduced hepatic and intestinal clearance of type 1 and type 2 cationic drugs compared with that in wild-type mice. These data strongly support the concept that mdr1-type P-gps are involved in the disposition of cationic amphiphilic drugs from the body. We tested the hypothesis that mdr1-type P-gps are involved in the transmembrane transport of organic cations in epithelial cells expressing various drug-transporting P-gps. Therefore, transepithelial transport of the P-gp substrate vinblastine, the steroidal (type 2) cation vecuronium, the relatively small (type 1) cationic compound azidoprocainamide methoiodide and the aliphatic cation tri-n-butylmethylammonium were measured. Apical expression of the mdr1a, mdr1b or MDR1 gene in confluently grown polarized transformed LLC-PK1 cells resulted in highly enhanced apical directed secretion of all the drugs tested compared with controls. The vectorial transport of tri-n-butylmethylammonium in the apical direction in the P-gp (over)expressing cells could be inhibited by vinblastine. The present observations show that apical secretion of type 1 as well as of type 2 organic cations is enhanced significantly in the presence of apical expressed mdr1-type P-gp. These findings provide evidence for the involvement of drug-transporting P-gp in transmembrane transport of various organic cations, including relatively small molecular weight aromatic and aliphatic compounds.
authors.affiliation: Department of Pharmacokinetics and Drug Delivery, University Center for Pharmacy, Groningen Institute for Drug Studies, Amsterdam, The Netherlands.
authors.forename: J W
authors.initials: JW
authors.lastname: Smit
authors.forename: B
authors.initials: B
authors.lastname: Weert
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
authors.forename: D K
authors.initials: DK
authors.lastname: Meijer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D016764:Cell Polarity; D004848:Epithelium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000493:pharmacokinetics; D013552:Swine; D014673:Vecuronium Bromide / Q000493:pharmacokinetics
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000644:Quaternary Ammonium Compounds; C043902:tri-n-butylmethylammonium; D014673:Vecuronium Bromide