title: First detection and quantification of N(δ)-monomethylarginine, a structural isomer of N(G)-monomethylarginine, in humans using MS(3).
abstract: The L-arginine metabolites methylated at the guanidino moiety, such as N(G)-monomethyl-L-arginine (LNMMA), asymmetric N(G),N(G)-dimethyl-L-arginine (ADMA), and symmetric N(G),N(G')-dimethyl-L-arginine (SDMA), are long known to be present in human plasma. Far less is known about the structural isomer of LNMMA, N(δ)-monomethyl-L-arginine (δ-MMA). In prior work, it has been detected in yeast proteins, but it has not been investigated in mammalian plasma or cells. In this work, we present a method for the simultaneous and unambiguous quantification of LNMMA and δ-MMA in human plasma that is capable of detecting δ-MMA separately from LNMMA. The method comprises a simple protein precipitation sample preparation, hydrophilic interaction liquid chromatography (HILIC) gradient elution on an unmodified silica column, and triple stage mass spectrometric detection. Stable isotope-labeled D6-SDMA was used as internal standard. The calibration ranges were 25-1000 nmol/L for LNMMA and 5-350 nmol/L for δ-MMA. The intra- and inter-batch precision determinations resulted in relative standard deviations of less than 12% for both compounds with accuracies of less than 6% deviation from the expected values. In a pilot study enrolling 10 healthy volunteers, mean concentrations of 48.0 ± 7.4 nmol/L for LNMMA and 27.4 ± 7.7 nmol/L for δ-MMA were found.
authors.affiliation: Institute of Clinical Pharmacology, Otto von Guericke University, 39120 Magdeburg, Germany. Electronic address: jens.martens-lobenhoffer@med.ovgu.de.
authors.forename: Jens
authors.initials: J
authors.lastname: Martens-Lobenhoffer
authors.affiliation: Institute of Clinical Pharmacology, Otto von Guericke University, 39120 Magdeburg, Germany.
authors.forename: Stefanie M
authors.initials: SM
authors.lastname: Bode-Böger
authors.affiliation: Pharmaceutical Institute, Christian Albrechts University, 24118 Kiel, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Clement
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D007536:Isomerism; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008875:Middle Aged; D010865:Pilot Projects; D015203:Reproducibility of Results; D055815:Young Adult; D019323:omega-N-Methylarginine / Q000032:analysis / Q000097:blood*
chemical_list: D019323:omega-N-Methylarginine
keywords: HILIC; Human plasma; MS(3); N(G)-monomethyl-l-arginine; N(δ)-monomethyl-l-arginine