Macrophages can convert citrulline into arginine.
Guoyao Wu,John T. Brosnan +1 more
TLDR
The results demonstrate that citrulline, produced by NO synthetase, can be recycled to arginine in macrophages, and may contribute to the regulation of intracellular availability of argininine and thus the prolonged production of NO by macrophage.Abstract:
Rat peritoneal macrophages were incubated in the presence of 0.05-1.0 mM-[14C]citrulline. The synthesis of [14C]arginine from 0.1 mM-[14C]citrulline was about 300 pmol/h per 10(6) cells in macrophages from saline-injected (control) rats. Both arginine synthesis from citrulline and nitrate production (an indicator of NO generation) were increased about 3-fold in the cells from lipopolysaccharide (LPS)-treated animals. The arginine synthesis was very sensitive to extracellular citrulline concentration in the range found in plasma (0.05-0.1 mM). The rate of arginine synthesis from citrulline was inhibited by about 20% by 0.5 mM-L-glutamine in both control and LPS-treated rat cells, but was inhibited by 0.5 mM-L-arginine only in control cells. Our results demonstrate that citrulline, produced by NO synthetase, can be recycled to arginine in macrophages. The citrulline-arginine cycle may contribute to the regulation of intracellular availability of arginine and thus the prolonged production of NO by macrophages.read more
Citations
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Amino acids and immune function
TL;DR: Increasing evidence shows that dietary supplementation of specific amino acids to animals and humans with malnutrition and infectious disease enhances the immune status, thereby reducing morbidity and mortality.
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Arginine metabolism and nutrition in growth, health and disease
Guoyao Wu,Guoyao Wu,Fuller W. Bazer,Teresa A. Davis,Sung Woo Kim,Peng Li,J. Marc Rhoads,M. Carey Satterfield,Stephen B. Smith,Thomas E. Spencer,Yulong Yin +10 more
TL;DR: The results of both experimental and clinical studies indicate that Arg is a nutritionally essential amino acid (AA) for spermatogenesis, embryonic survival, fetal and neonatal growth, as well as maintenance of vascular tone and hemodynamics and novel and effective therapies for obesity, diabetes, and the metabolic syndrome.
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Molecular Biology of Mammalian Plasma Membrane Amino Acid Transporters
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References
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