title: Multitracer stable isotope quantification of arginase and nitric oxide synthase activity in a mouse model of pseudomonas lung infection.
abstract: Cystic fibrosis airways are deficient for L-arginine, a substrate for nitric oxide synthases (NOSs) and arginases. The rationale for this study was to quantify NOS and arginase activity in the mouse lung. Anesthetized unventilated mice received a primed constant stable isotope intravenous infusion containing labeled L-arginine, ornithine, and citrulline. The isotopic enrichment of each of the infused isotopomers and its product amino acids were measured in plasma and organ homogenates using liquid chromatography-tandem mass spectrometry. The effect of infection was studied three days after direct tracheal instillation of Pseudomonas-coated agar beads. In the infusion model, lung infection resulted in a significant (28-fold) increase in NOS activity in lung but not in trachea, kidney, liver, or plasma. Absolute rates of arginase activity in solid tissues could not be calculated in this model. In an isolated lung perfusion model used for comparison increased NOS activity in infected lungs was confirmed (28.5-fold) and lung arginase activity was increased 9.7-fold. The activity of L-arginine metabolizing enzymes can be measured using stable isotope conversion in the mouse. Accumulation of L-ornithine in the whole mouse model hindered the exact quantification of arginase activity in the lung, a problem that was overcome utilizing an isolated lung perfusion model.
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Grasemann
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Division of Critical Care Medicine, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Thomas
authors.identifier: 0000-0002-8704-2419
authors.initials: T
authors.lastname: Jaecklin
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Anne
authors.identifier: 0000-0002-8700-6485
authors.initials: A
authors.lastname: Mehl
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Hailu
authors.identifier: 0000-0002-9708-1091
authors.initials: H
authors.lastname: Huang
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Mahroukh
authors.initials: M
authors.lastname: Rafii
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Paul
authors.initials: P
authors.lastname: Pencharz
authors.affiliation: Program in Physiology and Experimental Medicine, SickKids Research Institute and Division of Respiratory Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8 ; Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, Canada M5G 1X8.
authors.forename: Felix
authors.identifier: 0000-0003-4057-6592
authors.initials: F
authors.lastname: Ratjen
mesh_terms: D000818:Animals; D001119:Arginase / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D008168:Lung / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D011549:Pseudomonas / Q000472:pathogenicity*
chemical_list: D019001:Nitric Oxide Synthase; D001119:Arginase