Reduced citrulline availability by OTC deficiency in mice is related to reduced nitric oxide production.
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.
Luiking
Yvette C
YC
Univ. of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
Hallemeesch
Marcella M
MM
van de Poll
Marcel C
MC
Dejong
Cornelis H C
CH
de Jonge
Wouter J
WJ
Lamers
Wouter H
WH
Deutz
Nicolaas E P
NE
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
D002247:Carbon Isotopes; D008070:Lipopolysaccharides; D009587:Nitrogen Isotopes; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine; D003903:Deuterium