title: Scintillation proximity assay for measuring uptake by the human drug transporters hOCT1, hOAT3, and hOATP1B1.
abstract: Increasing evidence suggests a key role of transport proteins in the pharmacokinetics of drugs. Within the solute carrier (SLC) family, various organic cation transporters (OCTs), organic anion transporters (OATs), and organic anion transporting polypeptides (OATPs) that interact with drug molecules have been identified. Traditionally, cellular uptake assays require multiple steps and provide low experimental throughput. We here demonstrate the use of a scintillation proximity approach to detect substrate uptake by human drug transporters in real time. HEK293 cells stably transfected with hOCT1, hOATP1B1, or hOAT3 were grown directly in Cytostar-T scintillating microplates. Confluent cell monolayers were incubated with 14C- or 3H-labeled transporter substrates. Cellular uptake brings the radioisotopes into proximity with the scintillation plate base. The resulting light emission signals were recorded on-line in a microplate scintillation counter. Results show time- and concentration-dependent uptake of 14C-tetraethylammonium, 3H-methylphenylpyridinium (HEK-hOCT1), 3H-estradiol-17beta-D-glucuronide (HEK-hOATP1B1), and 3H-estrone-3-sulfate (HEK-hOAT3), while no respective uptake was detected in empty vector-transfected cells. Km of 14C-tetraethylammonium and 3H-estrone-3-sulfate uptake and hOAT3 inhibition by ibuprofen and furosemide were similar to conventional dish uptake studies. The scintillation proximity approach is high throughput, amenable to automation and allows for identification of SLC transporter substrates and inhibitors in a convenient and reliable fashion, suggesting its broad applicability in drug discovery.
authors.affiliation: Discovery DMPK&BA, AstraZeneca R&D Lund, 22187 Lund, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Lohmann
authors.forename: Birgitta
authors.initials: B
authors.lastname: Gelius
authors.forename: Jeanette
authors.initials: J
authors.lastname: Danielsson
authors.forename: Ulrica
authors.initials: U
authors.lastname: Skoging-Nyberg
authors.forename: Evelyn
authors.initials: E
authors.lastname: Hollnack
authors.forename: Adam
authors.initials: A
authors.lastname: Dudley
authors.forename: Johanna
authors.initials: J
authors.lastname: Wahlberg
authors.forename: Janet
authors.initials: J
authors.lastname: Hoogstraate
authors.forename: Lena
authors.initials: L
authors.lastname: Gustavsson
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000493:pharmacokinetics / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D002460:Cell Line; D005665:Furosemide / Q000493:pharmacokinetics / Q000494:pharmacology; D020719:Glucuronides / Q000493:pharmacokinetics; D006801:Humans; D007052:Ibuprofen / Q000493:pharmacokinetics / Q000494:pharmacology; D007700:Kinetics; D016014:Linear Models; D027381:Liver-Specific Organic Anion Transporter 1; D050811:Octamer Transcription Factor-1 / Q000235:genetics / Q000502:physiology*; D027361:Organic Anion Transporters / Q000235:genetics / Q000502:physiology*; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics / Q000502:physiology*; D010957:Plasmids / Q000235:genetics; D012588:Scintillation Counting; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology; D019789:Tetraethylammonium / Q000493:pharmacokinetics; D014162:Transfection; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D002247:Carbon Isotopes; D020719:Glucuronides; D027381:Liver-Specific Organic Anion Transporter 1; D050811:Octamer Transcription Factor-1; D027361:Organic Anion Transporters; D029362:Organic Anion Transporters, Sodium-Independent; C494165:POU2F1 protein, human; C503999:SLCO1B1 protein, human; D049994:Sodium Potassium Chloride Symporter Inhibitors; C114338:organic anion transport protein 3; D014316:Tritium; D019789:Tetraethylammonium; D005665:Furosemide; D007052:Ibuprofen