Simultaneous Determination of 6 L-Arginine Metabolites in Human and Mouse Plasma by Using Hydrophilic-Interaction Chromatography and Electrospray Tandem Mass Spectrometry

portant cellular mediators of the innate immune sys-tem and play important roles in wound healing and fibrosis. Flux through different L-arginine metabolic pathways partially defines the functional behavior of macrophages. Methods to measure metabolites within the nitric oxide synthase/arginase pathways could pro-vide insights into local and systemic inflammatory processes. METHODS: A targeted metabolomics approach was de-veloped by using hydrophilic-interaction liquid chro-matography and electrospray ionization–tandemmass spectrometry to simultaneously measure L-arginine, asymmetric dimethylarginine, symmetric dimethyl-arginine, L-citrulline, L-ornithine, and L-proline in plasma from humans and mice