title: Caki-1 cells as a model system for the interaction of renally secreted drugs with OCT3.
abstract: OBJECTIVE
  Organic cation transporters (OCT) in the proximal tubules (PTs) participate in the renal secretion of several therapeutic agents. The exact role of OCT3 in renal secretion remains undetermined, partially due to the lack of an appropriate in vitro model system. The current work introduces the PT representative cell line, Caki-1, as a model system for studying the involvement of OCT3 in renal secretion.
  
  
  METHODS
  Caki-1 cells were characterized for OCT3 expression via real-time RT-PCR and immunocytochemical staining techniques. Uptake kinetics of OCT3 in Caki-1 cells was determined using prototypical substrates and inhibitors. Inhibition of OCT3-mediated uptake via several renally secreted drugs and those specifically of quaternary ammonium structure were determined.
  
  
  RESULTS
  OCT3 expression was confirmed at the gene level and subcellular localization to the basolateral membrane (BLM) was illustrated for the first time. Caki-1 cells exhibited trademark kinetics of OCT3 and interacted with all therapeutic agents tested with varying affinities. The apparent IC(50 )values for cimetidine and trimethoprim were pharmacologically relevant.
  
  
  CONCLUSIONS
  Confirmation for the usefulness of Caki-1 cells as a PT model system for investigations of OCT3 was obtained, a novel BLM localization of OCT3 was possible and relevant interactions between OCT3 and renally secreted drugs were shown.
authors.affiliation: Institute of Pharmacy, Johannes Gutenberg University, Mainz, Germany.
authors.forename: Natalie
authors.initials: N
authors.lastname: Glube
authors.forename: Peter
authors.initials: P
authors.lastname: Langguth
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007700:Kinetics; D027701:Organic Cation Transport Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D027702:Organic Cation Transporter 1 / Q000235:genetics / Q000378:metabolism; D000075102:Organic Cation Transporter 2; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D015262:Xenobiotics / Q000378:metabolism / Q000494:pharmacology*; D000099254:Organic Cation Transporter 3
chemical_list: D015655:1-Methyl-4-phenylpyridinium; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D015262:Xenobiotics; D000099254:Organic Cation Transporter 3; C491013:SLC22A2 protein, human