Quantitative in vivo assessment of arginine utilization and nitric oxide production in endotoxemia.
BACKGROUND
Until recently no methods were available to quantitate nitric oxide (NO) production in vivo. The advent of stable isotope techniques has allowed quantitation of NO production in different animal models and human disease states.


METHODS
In vivo NO production was assessed with the use of stable isotope labeled arginine. Enrichments of metabolites were measured by liquid chromatography-mass spectrometry (LC-MS). Knock-out mice were used to assess the influence of knocking out inducible NOS (iNOS) or constitutively expressed NOS (cNOS) on arginine-NO metabolism. Pig models were used to assess the role of individual organs on arginine-NO fluxes.


RESULTS
In mice under basal conditions cNOS mediates half of the NO production. After endotoxin challenge NO production doubles as a result of iNOS induction and cNOS-mediated NO production is downregulated. In larger animal models (pig) whole body NO production is augmented after endotoxin challenge, largely resulting from NO production in liver, intestine and kidney. Arginine supplementation increases NO production in pigs in liver, intestine and kidney both in the basal state and after endotoxin challenge.


CONCLUSIONS
Stable isotope techniques employing LC-MS allow in vivo assessment of NO production in small and large animal models and in patients. This allows definition of the role that iNOS and cNOS-mediated NO production play in several disease states.
Soeters
Peter B
PB
Department of Surgery, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. pb.soeters@ah.unimaas.nl
Hallemeesch
Marcella M
MM
Bruins
Maaike J
MJ
van Eijk
Hans M H
HM
Deutz
Nicolaas E P
NE
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D002853:Chromatography, Liquid / Q000379:methods; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000009:adverse effects; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000032:analysis / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009587:Nitrogen Isotopes; D020033:Protein Isoforms / Q000378:metabolism; D018805:Sepsis / Q000209:etiology / Q000378:metabolism*; D013552:Swine
D008070:Lipopolysaccharides; D009587:Nitrogen Isotopes; D020033:Protein Isoforms; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase