Urea synthesis after oral protein ingestion in man.

Rafoth, Richard J.; Onstad, Gerald R.

doi:10.1172/jci108193

Cited by 79 publications

(29 citation statements)

References 14 publications

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“…This regression line indicates that for an increase in plasma amino nitrogen of 100 mmol 1-1 there is an increase in urea production of 155 mol min-.1 A similar relationship has been described in man following high protein meals (Rafoth & Onstad, 1975) or amino acid infusion (Vilstrup, 1980). In man an increase of 1 00 mmol 1-1 in plasma amino nitrogen was accompanied by an increase in urea production of 200-300 ,umol min- (Vilstrup, 1980).…”

Section: Plasma Amino Nitrogen After Amino Acidssupporting

confidence: 60%

Amino Nitrogen Metabolism Following Administration of Individual Amino Acids or Meat in Conscious Dogs

Lee

Summerill

1982

Exp Physiol

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Normal conscious dogs were given a meal of meat or doses of individual amino acids by stomach tube. The concentration of amino nitrogen in systemic arterial plasma and the rate of urea production both increased; the magnitude and time course of these increases varied with the individual amino acid administered. There was a relationship between the plasma amino nitrogen concentration and urea production following L‐serine, L‐alanine, L‐proline, dicarboxylic acids and L‐cystine similar to that obtained after meat ingestion. It is suggested that these amino acids were transaminated as rapidly as they were absorbed to produce an increase in a general pool of amino acids. Following L‐threonine, L‐valine, D‐serine and immediately after glycine, a small increase in urea production was accompanied by a large increase in plasma amino nitrogen concentration. It is suggested that these amino acids ‘escaped' transamination in the gut wall and liver and that the increase in plasma amino nitrogen was due to a high concentration of the individual amino acid administered.

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Section: Plasma Amino Nitrogen After Amino Acidssupporting

confidence: 60%

Amino Nitrogen Metabolism Following Administration of Individual Amino Acids or Meat in Conscious Dogs

Lee

Summerill

1982

Exp Physiol

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“…The rate of urea synthesis is directly dependent on nitrogen intake and protein breakdown, reflected by the plasma concentration of ␣-AN (1,9,22,34). This was also shown in the present study by the correlation between ␣-AN levels and urea synthesis rate.…”

Section: Discussionsupporting

confidence: 87%

Effect of major liver resection on hepatic ureagenesis in humans

Poll

Wigmore²,

Redhead³

et al. 2007

American Journal of Physiology-Gastrointestinal and Liver Physi

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Changes in hepatic ureagenesis following major hepatectomy are not well characterized. We studied the relation between urea synthesis and liver mass before and after major hepatectomy in humans. Fifteen patients scheduled for resection of malignancies in otherwise healthy livers were studied. Pre- and postoperative liver volume was assessed by computerized tomography-volumetry. During surgery, a primed, continuous infusion of [(13)C]urea was administered intravenously, and arterial blood samples were obtained hourly. Indocyanine green clearance was determined before and after resection. Seven patients underwent major hepatectomy, and eight patients underwent minor [<5% functional liver volume (total volume -- tumor volume)] or no resection, serving as controls. Resected functional liver volume in the major hepatectomy group averaged 60%. Urea synthesis per gram of functional liver tissue increased 2.6-fold following major hepatectomy, maintaining whole body urea synthesis. Arterial ammonia remained unchanged throughout the study, whereas following hepatectomy a hyperaminoacidemia occurred. In conclusion, immediately following major hepatectomy, urea synthesis per gram of functional liver tissue increases rapidly and proportionately to the amount of liver tissue resected, maintaining whole body urea synthesis at preoperative levels. This rapid and complete adaptation suggests that the capacity of urea synthesis is not limiting the maximum resectable volume in otherwise healthy livers.

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“…These properties include the following: (1) a very large capacity for hepatic urea production from amino acids, (2) urea is the major circulating pool of nitrogen and it crosses cell membranes readily so there is no gradient from intracellular to extracellular fluid under steady-state conditions, and (3) the volume of distribution of urea is the same as water (the urea space is estimated as 60% of body weight) (86)(87)(88).…”

Section: Clinical Usesmentioning

confidence: 99%

“…By varying the amount of dietary protein, changes in the diet can be integrated with different values of the S SUN. As shown in Table 1, similar concepts can be used to determine whether a patient is complying with the prescribed protein content of the diet (81,86,88).…”

Section: Clinical Usesmentioning

confidence: 99%

Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion

Weiner

Mitch

Sands

2015

Clinical Journal of the American Society of Nephrology

348

265

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Renal nitrogen metabolism primarily involves urea and ammonia metabolism, and is essential to normal health. Urea is the largest circulating pool of nitrogen, excluding nitrogen in circulating proteins, and its production changes in parallel to the degradation of dietary and endogenous proteins. In addition to serving as a way to excrete nitrogen, urea transport, mediated through specific urea transport proteins, mediates a central role in the urine concentrating mechanism. Renal ammonia excretion, although often considered only in the context of acidbase homeostasis, accounts for approximately 10% of total renal nitrogen excretion under basal conditions, but can increase substantially in a variety of clinical conditions. Because renal ammonia metabolism requires intrarenal ammoniagenesis from glutamine, changes in factors regulating renal ammonia metabolism can have important effects on glutamine in addition to nitrogen balance. This review covers aspects of protein metabolism and the control of the two major molecules involved in renal nitrogen excretion: urea and ammonia. Both urea and ammonia transport can be altered by glucocorticoids and hypokalemia, two conditions that also affect protein metabolism. Clinical conditions associated with altered urine concentrating ability or water homeostasis can result in changes in urea excretion and urea transporters. Clinical conditions associated with altered ammonia excretion can have important effects on nitrogen balance.

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Urea synthesis after oral protein ingestion in man.

Cited by 79 publications

References 14 publications

Amino Nitrogen Metabolism Following Administration of Individual Amino Acids or Meat in Conscious Dogs

Amino Nitrogen Metabolism Following Administration of Individual Amino Acids or Meat in Conscious Dogs

Effect of major liver resection on hepatic ureagenesis in humans

Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion

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