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Results for “AMINO ACID METABOLISM”

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At least 991 records · Page 55Linked to original sources
PubMed1989

Correction of amino acid metabolism by recombinant human erythropoietin therapy in hemodialysis patients.

We assessed the effect of correction of anemia with recombinant human erythropoietin (rhEPO) on plasma amino acid levels in maintenance hemodialysis patients. The plasma amino acid pattern was estimated by high performance liquid chromatography in 18 healthy persons and 14 hemodialysis patients before and up to 12 weeks after rhEPO therapy. There was a correction of the plasma serine values (67 +/- 16 to 87 +/- 22; P less than 0.05) and a corresponding decrease in the serine precursors, glycine (317 +/- 113 to 228 +/- 56; P less than 0.05) and hydroxyproline (26 +/- 21 to 15 +/- 13; P less than 0.10). The low plasma branched-chain amino acids, valine (137 +/- 33 to 154 +/- 50; P less than 0.10) and leucine (72 +/- 22 to 80 +/- 27; P less than 0.20), also were corrected. The elevated values of ornithine (78 +/- 16 to 62 +/- 19; P less than 0.1) and arginine (94 +/- 14 to 72 +/- 14; P less than 0.1) fell. The diminished glutamine values (470 +/- 125 to 563 +/- 115; P less than 0.1) and the decreased tyrosine/phenylalanine ratio (0.78 +/- 0.17 to 0.98 +/- 0.21; P less than 0.05) rose. Thus, the administration of rhEPO not only affects erythropoiesis, but also corrects the plasma amino acid pattern towards normal.

Adult↗
PubMed1980

Ammonia and amino acid metabolism y the portal-vein-drained viscera in chronic renal insufficiency.

Arterial portal-venous differences (A-PV) of ammonia (NH3) and amino acids (AA) were measured in patients with chronic renal insufficiency (CRI) and in controls. In CRI, NH3 release by the portal-vein-drained viscera (PDV) is not different from controls, Gln uptake decreases, Glu extraction occurs, Pro and Thr output increases and Ser release becomes evident; one third of N released as NH3 and AA can be accounted for by Gln and Glu uptake. The N exchange across the PDV is similar in CRI and in controls.

Adult↗
PubMed1992

Amino acid metabolism during platelet storage for transfusion.

Previous studies indicated that the concentration of ammonia rises during storage of platelet concentrates (PC) at 22 degrees C for transfusion and that fuels other than glucose are important for metabolism. Therefore, in the current study, we measured the concentrations of 17 plasma amino acids during PC storage; 16 of these either rose or were unchanged while the concentration of glutamine fell to zero by day 4. As the concentration of glutamine fell, the concentration of glutamate rose with a relationship suggesting that 65-75% of the glutamine was metabolized no further than glutamate. Phosphate-dependent glutaminase activity was present in platelets at 22.3 +/- 6.3 nmol/min/mg protein, a level similar to that seen in lymphocytes and macrophages. Leucodepletion studies excluded a significant contribution of contaminating leucocytes to these measurements. Thrombin stimulation did not increase the rate of glutamine metabolism. Analysis of the rates of glutamine metabolism suggests that it accounts for most of the ammonia produced during PC storage. However, it appears to be relatively insignificant as a metabolic fuel. The role of glutamine metabolism for platelets is uncertain. It may be a vestige of a pathway in the megakaryocyte. The ammonia which it produces may be deleterious for platelets and for patients with liver disease who receive PC infusions.

Amino Acids↗
PubMed1986

Dynamic aspects of amino acid metabolism in alloxan-induced diabetes and insulin-treated rabbits: in vivo studies with 15N and gas chromatography-mass spectrometry.

The present study was designed to determine the effect of alloxan-induced diabetes in rabbits on L-[15N]alanine and [15N]glycine kinetic parameters. This process was measured by single-dose administration of 15N-labeled amino acids to postabsorptive control rabbits and alloxan-induced diabetics and insulin-treated diabetic rabbits. Gas chromatography-mass spectrometry was used to determine the 15N enrichment of plasma glycine and alanine. Glycine and alanine pools and turnover rate constants were estimated from isotope enrichment time decay curves. The data from the present study indicate that plasma glycine and alanine turnover rate constants increased by 25-50% after alloxan administration but pool sizes showed only little changes, resulting in highly significant increases in fluxes and metabolic clearance rates of both alanine and glycine following alloxan administration; single-dose crystalline insulin or protamine zinc insulin treatment failed to restore the turnover rate constants of glycine or alanine toward control values and caused a depletion of 50% in glycine pool size; 7 days prolonged treatment with protamine zinc insulin restored alanine and glycine fluxes and metabolic clearance rates towards control postabsorptive values; and the reduction in flux values following insulin treatment is consistent with the reduction in the plasma glucose levels in rabbits. The data suggest that the regulatory mechanisms for uptake and metabolism of circulating glycogenic amino acids no longer are operative as a consequence of insulin deficiency following alloxan administration. Exogenous insulin restored the activity of the regulatory mechanism toward the postabsorptive control state.

Alanine↗
PubMed2000

Branched-chain L-amino acid metabolism in classical maple syrup urine disease after orthotopic liver transplantation.

We characterized the effect of orthotopic liver transplantation on the catabolism of branched-chain L-amino acids in a female patient with classical form of maple syrup urine disease. Transplantation was performed at the age of 7.4 years due to a terminal liver failure triggered by a hepatitis A infection. Since then, the patient is on an unrestricted diet and plasma concentrations of branched-chain L-amino and 2-oxo acids are stable, yet at moderately increased levels (2- to 3-fold of control). L-Alloisoleucine concentrations, however, remained remarkably elevated (> 5-fold of control). In vivo catabolism was investigated by measuring the metabolic L-alloisoleucine clearance and whole-body leucine oxidation in the postabsorptive state. In an oral loading test with 580 micromol alloisoleucine per kg body wt, the L-alloisoleucine elimination rate constant (0.067 h(-1)) was in the normal range (0.069+/-0.012 h(-1), n = 4). In an oral L-[1-13C]leucine load (38 micromol/kg body wt), 19.5% of the tracer dose applied was recovered in exhaled 13CO2 versus 18.9+/-3.6% in healthy subjects (n = 10). Thus, the patient exhibited obviously normal whole-body catabolic rates although branched-chain L-amino acid oxidation was confined to the liver transplant. Most likely, the enhanced substrate supply from extrahepatic sources led to an elevation of the plasma concentrations and thus induced a compensatory enhancement of the metabolic flux through the branched-chain 2-oxo acid dehydrogenase complex in the intact liver tissue.

Adolescent↗
PubMed1989

Amino acid metabolism in muscle and in the whole body of man before and after ingestion of a single mixed meal.

Whole-body energy expenditure, protein oxidation, and exchange of amino acids, glutathione, and other metabolites across forearm muscle were assessed before and for 4 h after ingestion of a single meal containing 3274 kJ (783 kcal) and 25.5 g protein (4.08 g nitrogen). The study 1) demonstrates the dominance of glutamine over all other amino acids in carrying N out of skeletal muscle (1.33 mumol.L muscle-1.min-1 between 0 and 4 h--equivalent to 71% of the amino acid release or 82% of the amino acid N release); 2) suggests that glucose-alanine recycling between muscle and liver is not increased in the postprandial period despite the large uptake of glucose by muscle; 3) provides no support for the hypothesis that a substantial amount of N is exchanged between blood and muscle in the form of glutathione; and 4) considers the overall quantitative importance of amino acid oxidation in the whole body and the accompanying exchange of amino acids in skeletal muscle.

Adult↗