title: Transport of asymmetric dimethylarginine (ADMA) by cationic amino acid transporter 2 (CAT2), organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1).
abstract: Asymmetric dimethylarginine (ADMA), inhibiting the nitric oxide (NO) synthesis from L-arginine, is a known cardiovascular risk factor. Our aim was to investigate if ADMA and/or L-arginine are substrates of the human cationic amino acid transporters 2A (CAT2A, SLC7A2A) and 2B (CAT2B, SLC7A2B), the organic cation transporter 2 (OCT2, SLC22A2), and the multidrug and toxin extrusion protein 1 (MATE1, SLC47A1). We systematically investigated the kinetics of ADMA and L-arginine transport in human embryonic kidney (HEK293) cells stably overexpressing CAT2A, CAT2B, OCT2, or MATE1. Vector-only transfected HEK293 cells served as controls. Compared to vector control cells, uptake of ADMA and L-arginine was significantly higher (p < 0.05) in cells expressing CAT2B and OCT2 at almost all investigated concentrations, while cells expressing CAT2A only showed a significant uptake at concentrations above 300 μM. Uptake of MATE1 overexpressing cells was significantly (p < 0.05) higher at pH 7.8 and 8.2 than controls. Apparent V max values (nmol mg protein(-1) min(-1)) for cellular uptake of ADMA and L-arginine were ≈11.8 ± 1.2 and 19.5 ± 0.7 for CAT2A, ≈14.3 ± 1.0 and 15.3 ± 0.4 for CAT2B, and 6.3 ± 0.3 and >50 for OCT2, respectively. Apparent K m values (μmol/l) for cellular uptake of ADMA and L-arginine were ≈3,033 ± 675 and 3,510 ± 419 for CAT2A, ≈4,021 ± 532 and 952 ± 92 for CAT2B, and 967 ± 143 and >10,000 for OCT2, respectively. ADMA and L-arginine are substrates of human CAT2A, CAT2B, OCT2 and MATE1. Transport kinetics of CAT2A, CAT2B, and OCT2 indicate a low affinity, high capacity transport, which may be relevant for renal and hepatic elimination of ADMA or L-arginine.
authors.affiliation: Emil Fischer Center, Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstraße 17, 91054, Erlangen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Strobel
authors.forename: Fabian
authors.initials: F
authors.lastname: Müller
authors.forename: Oliver
authors.initials: O
authors.lastname: Zolk
authors.forename: Beate
authors.initials: B
authors.lastname: Endreß
authors.forename: Jörg
authors.initials: J
authors.lastname: König
authors.forename: Martin F
authors.initials: MF
authors.lastname: Fromm
authors.forename: Renke
authors.initials: R
authors.lastname: Maas
mesh_terms: D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D027701:Organic Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D011499:Protein Processing, Post-Translational; D060888:Real-Time Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; C491013:SLC22A2 protein, human; C521869:SLC47A1 protein, human; D050916:TRPV Cation Channels; C492239:TRPV5 protein, human; C487735:dimethylarginine; D001120:Arginine