Urea cycle intermediate kinetics and nitrate excretion at normal and "therapeutic" intakes of arginine in humans

Beaumier, Louis; Castillo, Leticia; Ajami, Alfred M.; Young, Vernon R.

doi:10.1152/ajpendo.1995.269.5.e884

Cited by 54 publications

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“…Apenas a cGMP ou a concentração de citrulina podem ser usadas para obter informações quantitativas relacionadas com a quantidade de produção de NO 6 . A produção de NO também pode ser determinada pela mensuração de isótopos estáveis no plasma ou excretados na urina após administração de arginina marcada [64][65][66][67] . A mensuração direta do óxido nítrico in vivo foi realizada por HUK e col. (1997) 68 , que mediram a liberação do NO em microvasos da musculatura esquelética de coelhos, durante isquemia e reperfusão.…”

Section: Mensuração Do óXido Nítricounclassified

Óxido nítrico: revisão

Cerqueira¹,

Yoshida

2002

Acta Cir. Bras.

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INTRODUÇÃO. O NO tem alta afinidade com o heme, encontrado em proteínas intracelulares (óxido nítrico-sintase, cicloxigenase e guanilato ciclase) e também liga-se a grupos -SH, formando tiol 10 ; é um gás incolor e estável, moderadamente solúvel em água e sua meiavida varia de 3 a 60 segundos, mas pode ser maior devido ao ambiente do NO, concentração de O 2 e O· 2 - 6,[11][12][13][14][15][16] . Parece que o NO exerce maior efeito na imunidade inespecífica do que na específica, exibindo atividade citostática ou citocida contra uma notável amplitude de microorganismos patogênicos 8,17 . PRODUÇÃO DE ÓXIDO NÍTRICOVárias células utilizam a arginina para sintetizar o óxido nítrico [18][19][20] . Nas células do endotélio vascular, na

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Section: Mensuração Do óXido Nítricounclassified

Óxido nítrico: revisão

Cerqueira¹,

Yoshida

2002

Acta Cir. Bras.

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“…Regardless of whether intravenous, IP, or IG fluxes are used for calculation purposes, the relative differences between diets in Q Pro3 Arg are real. Indeed, if splanchnic extraction is subtracted from the IG infusion dose to determine intravenous flux rates in the pigs of the present study (2), then the data would be approximately one-half in absolute value but would not change the statistical comparisons made. The major findings of this research confirm the existence of a basal and a maximal rate of arginine synthesis and of dietary regulation of arginine synthesis from proline.…”

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confidence: 91%

Arginine synthesis is regulated by dietary arginine intake in the enterally fed neonatal piglet

Wilkinson¹,

Bertolo²,

Brunton³

et al. 2004

American Journal of Physiology-Endocrinology and Metabolism

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Arginine is conditionally indispensable in the neonate, and its synthesis in the intestine is not sufficient to meet requirements. It is not known how neonatal endogenous arginine synthesis is regulated and the degree to which proline and glutamate are used as precursors. Primed, constant intraportal and intragastric infusions of L-[U-14 C]proline and L- [3,4-3 H]glutamate, and intragastric L-[guanido-14 C]arginine were used to measure whole body and first-pass intestinal arginine synthesis in 10 neonatal piglets fed generous (1.80) quantities of arginine for 5 days. Glutamate tracer was not detected in arginine, indicating a biologically insignificant conversion of Ͻ1% of arginine flux. Endogenous arginine synthesis from proline had obligatory (0.36 g ⅐ kg Ϫ1 ⅐ day Ϫ1 ) and maximal (0.68 g ⅐ kg Ϫ1 ⅐ day Ϫ1 ) levels (P Ͻ 0.05, pooled SE 0.05). Although first-pass gut metabolism is responsible for 42-63% of whole body arginine synthesis, the gut is incapable of upregulating proline to arginine conversion during arginine deficiency, compared with a more than threefold increase without firstpass gut metabolism. These data suggest that upregulation of prolineto-arginine conversion occurs via increased arterial extraction of proline by the gut or in nonintestinal tissues. This study demonstrates that dietary arginine is an important regulator of endogenous arginine synthesis in the neonatal piglet and that proline, but not glutamate, is an important precursor for arginine synthesis in the neonate.

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“…First, the metabolic fate of the remarkably increased uteroplacental utilization and fetal arginine concentration is unknown. In a study of whole-body arginine kinetics in healthy adult males at both normal and 10 times normal arginine dietary intakes, both plasma arginine and ornithine fluxes, as well as conversion of arginine to ornithine, were significantly increased, whereas there was no apparent increase in nitric oxide from arginine (24). Plasma insulin concentrations were significantly increased in the high-arginine intake group.…”

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confidence: 95%

Ovine Placental and Fetal Arginine Metabolism at Normal and Increased Maternal Plasma Arginine Concentrations

et al. 2002

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Arginine (A) may play a significant role in fetal growth, by stimulating insulin secretion and as a precursor for both polyamine synthesis and nitric oxide production. To determine whether increased maternal plasma A concentrations can enhance delivery of A to the fetus, uterine, umbilical, and net uteroplacental (UP) A uptake rates were measured in 12 pregnant ewes at 129.6 Ϯ 0.4 d gestation (mean Ϯ SEM) during normal and after 3 h of increased maternal plasma A concentrations. With a 2.7-fold increase in maternal plasma A concentrations (p Ͻ 0.001), there were significant increases in uterine A uptake (13.8 Ϯ 1.0 to 41.3 Ϯ 7.7 mol/min, p Ͻ 0.005), umbilical A uptake (3.3 Ϯ 0.5 to 5.2 Ϯ 0.8 mol·min Ϫ1 ·kg Ϫ1 fetus, p Ͻ 0.005), UP A uptake (17.8 Ϯ 6.2 to 89.2 Ϯ 20.3 mol·min Ϫ1 ·kg Ϫ1 placenta, p Ͻ 0.01), fetal arterial A concentration (98.7 Ϯ 6.3 to 137.1 Ϯ 9.9 M, p Ͻ 0.001), maternal A disposal rate (143.7 Ϯ 9.4 to 217.0 Ϯ 6.7 mol/min, p Ͻ 0.001), fetal A disposal rate (7.9 Ϯ 0.8 to 9.9 Ϯ 1.1 mol·min Ϫ1 ·kg Ϫ1 , p Ͻ 0.05), fetal A oxidation rate (1.31 Ϯ 0.24 to 1.84 Ϯ 0.36 mol·min Ϫ1 ·kg Ϫ1 , p Ͻ 0.05), and plasma insulin concentration in both fetus (16 Ϯ 2 to 20 Ϯ 2 U/mL, p Ͻ 0.001) and mother (24 Ϯ 3 to 32 Ϯ 4 U/mL, p Ͻ 0.001). Thus, increased maternal plasma A concentration increases maternal, UP, and fetal A net uptake, and increases insulin secretion in mother and fetus. The 4.2-fold larger increase in UP than net fetal A uptake could represent preferential UP A metabolism relative to fetal A metabolism, relatively limited placental-fetal A transport capacity compared with uterine A uptake capacity, or both; responsible mechanisms remain unknown. Arginine is a conditionally indispensable amino acid in the mammalian fetus and neonate (1, 2), and maintenance of fetal arginine supply and plasma concentrations are important for optimal fetal growth. The mechanisms by which arginine promotes fetal growth, however, are multifaceted and have not been adequately investigated. Arginine is an insulin secretagogue in ovine and human fetuses (3-7) and in human newborns (8 -10); thus the role of arginine in fetal growth may include an insulin-mediated anabolic effect. In addition, arginine could stimulate growth as a precursor for polyamine synthesis (11) and nitric oxide production (12-14).In contrast, arginine deficiency has been shown to induce growth restriction in experimental animals (15, 16). A potential therapy for fetal growth restriction, therefore, could include maternal plasma arginine supplementation in an attempt to increase fetal arginine supply. It is not known, however, whether increasing maternal plasma arginine concentration could increase net fetal arginine uptake, fetal plasma arginine concentration, or fetal insulin concentration. In addition, the characteristics of placental arginine uptake, metabolism, and transport to the fetus have not been determined. Therefore, this study was designed to determine how maternal arginine supplementation affects maternal, uteroplacental, and fetal arginine net ...

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Urea cycle intermediate kinetics and nitrate excretion at normal and "therapeutic" intakes of arginine in humans

Cited by 54 publications

References 0 publications

Óxido nítrico: revisão

Óxido nítrico: revisão

Arginine synthesis is regulated by dietary arginine intake in the enterally fed neonatal piglet

Ovine Placental and Fetal Arginine Metabolism at Normal and Increased Maternal Plasma Arginine Concentrations

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