title: Detection and quantification of α-keto-δ-(N(G),N(G)-dimethylguanidino)valeric acid: a metabolite of asymmetric dimethylarginine.
abstract: Nitric oxide is an ubiquitary cell signaling substance. Its enzymatic production rate by nitric oxide synthase is regulated by the concentrations of the substrate L-arginine and the competitive inhibitor asymmetric dimethylarginine (ADMA). A newly recognized elimination pathway for ADMA is the transamination to α-keto-δ-(N(G),N(G)-dimethylguanidino)valeric acid (DMGV) by the enzyme alanine-glyoxylate aminotransferase 2 (AGXT2). This pathway has been proven to be relevant for nitric oxide regulation, but up to now no method exists for the determination of DMGV in biological fluids. We have developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of DMGV. D(6)-DMGV was used as internal standard. Samples were purified online by column switching, and separation was achieved on a porous graphitic carbon column. The calibration was linear over ranges of 10 to 200 nmol/L for plasma and 0.1 to 20 μmol/L for urine. The intra- and interday accuracies and precisions in plasma and urine were better than 10%. In plasma samples, DMGV was present in concentrations between 19.1 and 77.5 nmol/L. In urine samples, concentrations between 0.0114 and 1.03 μmol/mmol creatinine were found. This method can be used as a tool for the scientific investigation of the ADMA conversion to DMGV via the enzyme AGXT2.
authors.affiliation: Institute of Clinical Pharmacology, Otto-von-Guericke University, 39120 Magdeburg, Germany. jens.martens-lobenhoffer@med.ovgu.de
authors.forename: Jens
authors.initials: J
authors.lastname: Martens-Lobenhoffer
authors.forename: Roman N
authors.initials: RN
authors.lastname: Rodionov
authors.forename: Andreas
authors.initials: A
authors.lastname: Drust
authors.forename: Stefanie M
authors.initials: SM
authors.lastname: Bode-Böger
mesh_terms: D000328:Adult; D001120:Arginine / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D001671:Biochemistry / Q000379:methods*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006146:Guanidines / Q000032:analysis* / Q000097:blood / Q000737:chemistry / Q000652:urine; D006801:Humans; D007651:Keto Acids / Q000032:analysis* / Q000097:blood / Q000737:chemistry / Q000652:urine; D057230:Limit of Detection; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged
chemical_list: D006146:Guanidines; D007651:Keto Acids; C569758:alpha-keto-delta-(NG,NG-dimethylguanidino)valeric acid; C018524:N,N-dimethylarginine; D001120:Arginine