title: Reduced citrulline availability by OTC deficiency in mice is related to reduced nitric oxide production.
abstract: The amino acid arginine is the sole precursor for nitric oxide (NO) synthesis. We recently demonstrated that an acute reduction of circulating arginine does not compromise basal or LPS-inducible NO production in mice. In the present study, we investigated the importance of citrulline availability in ornithine transcarbamoylase-deficient spf(ash) (OTCD) mice on NO production, using stable isotope techniques and C57BL6/J (wild-type) mice controls. Plasma amino acids and tracer-to-tracee ratios were measured by LC-MS. NO production was measured as the in vivo conversion of l-[guanidino-(15)N(2)]arginine to l-[guanidine-(15)N]citrulline; de novo arginine production was measured as conversion of l-[ureido-(13)C-5,5-(2)H(2)]citrulline to l-[guanidino-(13)C-5,5-(2)H(2)]arginine. Protein metabolism was measured using l-[ring-(2)H(5)]phenylalanine and l-[ring-(2)H(2)]tyrosine. OTC deficiency caused a reduction of systemic citrulline concentration and production to 30-50% (P < 0.001), reduced de novo arginine production (P < 0.05), reduced whole-body NO production to 50% (P < 0.005), and increased net protein breakdown by a factor of 2-4 (P < 0.001). NO production was twofold higher in female than in male OTCD mice in agreement with the X-linked location of the OTC gene. In response to LPS treatment (10 mg/kg ip), circulating arginine increased in all groups (P < 0.001), and NO production was no longer affected by the OTC deficiency due to increased net protein breakdown as a source for arginine. Our study shows that reduced citrulline availability is related to reduced basal NO production via reduced de novo arginine production. Under basal conditions this is probably cNOS-mediated NO production. When sufficient arginine is available after LPS stimulated net protein breakdown, NO production is unaffected by OTC deficiency.
authors.affiliation: Univ. of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Yvette C
authors.initials: YC
authors.lastname: Luiking
authors.forename: Marcella M
authors.initials: MM
authors.lastname: Hallemeesch
authors.forename: Marcel C
authors.initials: MC
authors.lastname: van de Poll
authors.forename: Cornelis H C
authors.initials: CH
authors.lastname: Dejong
authors.forename: Wouter J
authors.initials: WJ
authors.lastname: de Jonge
authors.forename: Wouter H
authors.initials: WH
authors.lastname: Lamers
authors.forename: Nicolaas E P
authors.initials: NE
authors.lastname: Deutz
mesh_terms: D000818:Animals; D001120:Arginine / Q000378:metabolism / Q000493:pharmacokinetics; D001682:Biological Availability; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D002956:Citrulline / Q000378:metabolism / Q000493:pharmacokinetics*; D003903:Deuterium / Q000493:pharmacokinetics; D005260:Female; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000493:pharmacokinetics; D020163:Ornithine Carbamoyltransferase Deficiency Disease / Q000378:metabolism* / Q000473:pathology
chemical_list: D002247:Carbon Isotopes; D008070:Lipopolysaccharides; D009587:Nitrogen Isotopes; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine; D003903:Deuterium