title: Flow cytometric assessment of P-glycoprotein and multidrug resistance-associated protein activity and expression in canine lymphoma.
abstract: OBJECTIVE
  To investigate the activity and expression of P-glycoprotein (P-gp) and multidrug resistance-associated proteins (MRPs) in biopsy samples from lymph nodes of 22 dogs at the time of lymphoma diagnosis.
  
  
  METHODS
  Protein activity and expression were investigated by flow cytometry. Expression was assessed with monoclonal antibodies (C494 for P-gp and MRPm6 for MRP1). P-gp activity was determined by rhodamine 123 (Rho 123) efflux inhibited by verapamil and MRP by 5(6) carboxyfluorescein diacetate (CFDA) efflux inhibited by probenecid. Cell lineage was determined based on the expression of CD79α, CD21, CD3, CD4 and CD8.
  
  
  RESULTS
  P-gp and MRP1 were expressed in all samples. Relative activity was low for both transporters and no correlation was found between transporter activity and expression. The majority of lymphomas were of B-cell origin.
  
  
  CONCLUSIONS
  Low transporter activity and lack of correlation with expression suggest that spontaneous up-regulation of P-gp or MRP is not a common phenomenon in canine lymphoma.
authors.affiliation: Department of Biochemistry, Pharmacology and Toxicology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland blazej.pozniak@up.wroc.pl.
authors.forename: Błażej
authors.initials: B
authors.lastname: Poźniak
authors.affiliation: Department of Biochemistry, Pharmacology and Toxicology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Pawlak
authors.affiliation: Department of Biochemistry, Pharmacology and Toxicology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.
authors.forename: Bożena
authors.initials: B
authors.lastname: Obmińska-Mrukowicz
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001706:Biopsy; D004285:Dogs; D005434:Flow Cytometry; D015870:Gene Expression; D016130:Immunophenotyping; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D027425:ATP-Binding Cassette, Sub-Family C Proteins
keywords: MRP; P-gp; canine lymphoma; dye efflux assay; flow cytometry