title: Measurement of homoarginine in human and mouse plasma by LC-MS/MS and ELISA: a comparison and a biological application.
abstract: Homoarginine (hArg) is a non-essential amino acid that was identified as a risk marker for cardiovascular disease. Several analytical methods have been described for the quantification of hArg in biological samples. The aim of this study was to compare a liquid chromatography-tandem mass spectrometric (LC-MS/MS) approach with a commercially available enzyme-linked immunosorbent assay (ELISA). Determination of hArg concentrations in ELISA calibration standards measured by both methods revealed a correlation coefficient r (2) of 0.99, for LC-MS/MS calibrators r (2) was 0.997. However, linear regression analysis between the two assays for hArg concentrations in human plasma samples revealed a correlation coefficient r (2) of 0.78. Plasma concentrations obtained from LC-MS/MS are on average 29 % higher than those by ELISA. We investigated the hArg-isobaric N (ε)-trimethyllysine as potential source for the higher observed values, but evaluation of mass spectra indicated that N (ε)-trimethyllysine did not interfere with hArg quantification in our LC-MS/MS method. Both quantification methods were applied to measure hArg in (1) a case-control study of acute coronary syndrome and (2) L-arginine:glycine amidinotransferase-deficient mice. Our LC-MS/MS and the commercially available ELISA assay are suitable for hArg measurement in human and mouse plasma, but different reference values for each method need to be considered.
authors.affiliation: Department of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Cordts
authors.forename: Dorothee
authors.initials: D
authors.lastname: Atzler
authors.forename: Vazhma
authors.initials: V
authors.lastname: Qaderi
authors.forename: Karsten
authors.initials: K
authors.lastname: Sydow
authors.forename: Rainer H
authors.initials: RH
authors.lastname: Böger
authors.forename: Chi-Un
authors.initials: CU
authors.lastname: Choe
authors.forename: Edzard
authors.initials: E
authors.lastname: Schwedhelm
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006709:Homoarginine / Q000097:blood* / Q000235:genetics; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D018345:Mice, Knockout; D012680:Sensitivity and Specificity
chemical_list: D006709:Homoarginine