title: Evaluation of (99m)technetium-mebrofenin and (99m)technetium-sestamibi as specific probes for hepatic transport protein function in rat and human hepatocytes.
abstract: OBJECTIVE
  This study characterized 99mTc-Mebrofenin (MEB) and 99mTc-Sestamibi (MIBI) hepatic transport and preferential efflux routes (canalicular vs. basolateral) in rat and human sandwich-cultured hepatocytes (SCH).
  
  
  METHODS
  99mTc-MEB and 99mTc-MIBI disposition was determined in suspended hepatocytes and in SCH in the presence and absence of inhibitors and genetic knockdown of breast cancer resistance protein (Bcrp).
  
  
  RESULTS
  The general organic anion transporting polypeptide (Oatp/OATP) inhibitor rifamycin SV reduced initial 99mTc-MEB uptake in rat and human suspended hepatocytes. Initial 99mTc-MIBI uptake in suspended rat hepatocytes was not Na+-dependent or influenced by inhibitors. Multidrug resistance-associated protein (Mrp2/MRP2) inhibitors decreased 99mTc-MEB canalicular efflux in rat and human SCH. 99mTc-MEB efflux in human SCH was predominantly canalicular (45.8 +/- 8.6%) and approximately 3-fold greater than in rat SCH. 99mTc-MIBI canalicular efflux was similar in human and rat SCH; basolateral efflux was 37% greater in human than rat SCH. 99mTc-MIBI cellular accumulation, biliary excretion index and in vitro biliary clearance in rat SCH were unaffected by Bcrp knockdown.
  
  
  CONCLUSIONS
  99mTc-MEB hepatic uptake is predominantly Oatp-mediated with biliary excretion by Mrp2. 99mTc-MIBI appears to passively diffuse into hepatocytes; biliary excretion is mediated by P-gp. The SCH model is useful to investigate factors that may alter the route and/or extent of hepatic basolateral and canalicular efflux of substrates.
authors.affiliation: Division of Pharmacotherapy and Experimental Therapeutics UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7569, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Swift
authors.forename: Wei
authors.initials: W
authors.lastname: Yue
authors.forename: Kim L R
authors.initials: KL
authors.lastname: Brouwer
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000814:Aniline Compounds; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D005998:Glycine; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D007098:Imino Acids / Q000493:pharmacokinetics*; D008099:Liver / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000235:genetics; D027361:Organic Anion Transporters / Q000037:antagonists & inhibitors / Q000502:physiology; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D012294:Rifamycins / Q000494:pharmacology; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C489249:Abcg2 protein, rat; D000814:Aniline Compounds; D002352:Carrier Proteins; D007098:Imino Acids; D009363:Neoplasm Proteins; D027361:Organic Anion Transporters; D015609:Organotechnetium Compounds; D034741:RNA, Small Interfering; D012294:Rifamycins; D017256:Technetium Tc 99m Sestamibi; C023808:rifamycin SV; C034837:technetium Tc 99m mebrofenin; D005998:Glycine