Excretion Of Free Amino Acids Research Articles

Quantitative amino acid and proteomic analysis: Very low excretion of polypeptides >750 Da in normal urine

Quantitative data on protein and polypeptide excretion in normal urine are lacking. In Fanconi syndrome, failure of proximal tubular protein reabsorption leads to 'tubular' proteinuria, but little is known about peptide excretion. Urine from normal (N=5) and Fanconi patients (Dent's disease, N=2; Lowe syndrome, N=3) was fractionated by size-exclusion chromatography into proteins (>10 kD) and smaller polypeptides. Each fraction was subjected to amino acid analysis after acid hydrolysis. In complementary proteomic approaches, urinary polypeptides were each subjected to reversed-phase high-performance liquid chromatography (HPLC) followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and nano-flow liquid chromatography directly coupled to electrospray ionization/tandem mass spectrometry (NanoLC-ESI-MS/MS) before and after tryptic digestion. Based on amino acid composition, normal human urine, excluding Tamm-Horsfall protein, contains 33.7 +/- 10.7 mg protein per 24 hr (mean +/- SEM) protein defined as polypeptide >10 kD; peptide content in range 750 Da to 10 kD is 22.0 +/- 9.6 mg. Fanconi patients excrete greatly increased amounts of protein, 1740 +/- 660 mg/24 hr, and peptide, 446 +/- 145 mg/24 hr. Peptides 2 to 5 kD were present in 12.9- +/- 3.9-fold excess in Fanconi compared with normal urine. In contrast, free amino acid excretion in Fanconi was elevated only 2.14- +/- 0.73-fold. Mass spectrometric techniques determined that the major form of albumin in both normal and Fanconi urine was the full-length protein, and did not detect significant peptides of nonrenal origin. There is only very low excretion of polypeptides >750 Da in normal human urine. In Fanconi syndrome, excretion of unknown peptides of mass 2 to 5 kD, possibly relevant to the development of renal failure, is greatly increased.

Serum and urinary amino acid levels in sickle cell disease.

Neonates with sickle cell disease (SCD) are of normal size at birth in terms of height and weight. However, by the sixth month of life their growth begins to lag significantly behind that of non-sicklers. We hypothesize that such growth retardation could be explained, at least in part, by the increased excretion of free amino acids in the urine of children with SCD. It is well established that in SCD there are abnormalities in the proximal tubules where amino acids are reabsorbed. We collected serum and urine samples from 13 patients with SCD (age range, 10 months to 14 years), and 17 age-and gender-matched controls, and analysed these specimens for free amino acids and creatinine. The SCD population was less well nourished than the controls, as evidenced by the lower serum prealbumin levels in the former group (91.3 v. 127 mg/l, P = 0.01). The serum concentrations of all of the essential amino acids were significantly reduced (21-47 per cent, P < 0.01) in the SCD subjects, as were those of most of the non-essential amino acids (exceptions: alanine, glutamic acid, proline). The urine concentrations of seven of the essential amino acids (indexed to creatinine) were increased in the SCD children. The greatest difference in urinary amino acid excretion was seen with methionine; the SCD subjects excreted 3.6-fold more methionine than the controls. These data indicate that reduced levels of serum amino acids resulting from increased urinary loss of these amino acids in children with SCD could contribute to the decreased growth rates one sees in children with this genetically inherited hematologic disorder.

Sodium-dependent transport of amino acids in renal brush border membrane vesicles and urinary free amino acid excretion in rats.

The reabsorption of ammo acids in rat kidney was examined with respect to the Na+-gradient stimulated transport system. The time courses for the uptake of 14C-amino acids by brush border membrane vesicles were compared in the presence of either Na+ or K+ ions. The uptake of neutral amino acids was stimulated by the presence of a Na+-gradient and exhibited the typical overshoot phenomenon, whereas the uptake of acidic and basic amino acids was not clearly stimulated by Na+. The rate of Na+-dependent uptake into the vesicles at 1 min was determined for 20 amino acids, and was high for alanine, cysteine, valine and isoleucine but low in acidic and basic amino acids. In normal rat urine, the free forms of glycine, alanine and glutamic acid were excreted to a great extent, but isoleucine, arginine and sulfur-containing amino acids were excreted to a small extent. These results indicate that the urinary excretion of an amino acid is not necessarily correlated to the extent of its Na+-dependent uptake, and that other factors affecting the urinary excretion should also be considered.

Serum concentrations and urinary excretion of amino acids during total parenteral nutrition after abdominal surgery.

The effects of five days of postoperative total parenteral nutrition (TPN)—no oral intake—including a fat emulsion, Intralipid 20%, and varying amounts of amino acids and carbohydrates, on the fasting serum concentrations of amino acids, the nitrogen balance and the rate of urinary excretion of free amino acids were studied in three groups of patients, A, B and C, undergoing abdominal surgery. Group A was given 9.4 grams of nitrogen every 24 hours as 18 L‐amino acids in proportions corresponding to the amino acid composition of egg protein; groups B and C were given 9.3 and 13.9 grams of nitrogen every 24 hours, respectively, including the same 18 L‐amino acids in proportions corresponding to those present in human milk protein. During the first seven postoperative days, the changes in the serum concentrations of amino acids conformed largely to five patterns in all the groups. On day five, the serum concentration of methionine was higher in group B than in group C, whereas there was no difference in the urinary excretion rate for 3‐methylhistidine; this suggests that an increased supply of an amino acid may be reflected in a decrease in the fasting serum concentration of this amino acid administered. During the five days of TPN, the rate of urinary excretion of glycine and histidine decreased in all the groups. The 24‐hour urinary excretion of most of the amino acids administered was numerically greater in group C than in group B on all days studied with significant difference for methionine and valine on day five, whereas the excretion rate for amino acids expressed as a percentage of the total amount on a molar basis was similar for these groups. This suggests that an increase in the intravenous supply of amino acids in proportions corresponding to the amino acid composition of human milk protein is reflected in an increased rate of urinary excretion of the amino acids administered. The rate of urinary excretion of total nitrogen was similar in groups A and B. The nitrogen balance values showed efficient utilization of the two amino acids solutions studied, but no difference between them in this respect.

Intracellular Composition and Net Release Rates of Free Amino Acids in Daphnia magna

Excretion of free amino acids and ammonia by Daphnia magna was measured by examining in vitro changes in concentration of the two forms of nitrogen over 4–6 h. Mean weight-specific amino acid release rate (± SE) for 32 healthy daphnids was 0.13 ± 0.03 nmol (mg dry wt)−1∙h−1 as compared with a mean ammonia excretion rate of 21 ± 2 nmol (mg dry wt)−1∙h−1. Net removal from solution was observed when low levels of amino acids (2 nmol/8 mL) were added to the water before incubation, indicating that measured net release rates could be reduced by amino acid uptake. Toxic levels (0.5 mg∙L−1) of lead, arsenic, Kepone, toxaphene, malathion, or pentachlorophenol, added to stress the animals, did not significantly affect release rates of amino acids or ammonia, but the addition of copper (as CuSO4) increased amino acid release by daphnids and hindered microbial removal of amino acids from incubation waters. Amino acids released from copper-exposed animals were similar in composition to those in intracellular amino acid pools of D. magna, suggesting that diffusion across cell membranes may have been the mechanism for amino acid release.Key words: amino acids, ammonia, cladocera, contaminants, copper, Daphnia, excretion, free amino acids, stress, zooplankton

Salt and water balance in the oligohaline clam, Rangia cuneata III. Reduction of the free amino acid pool during low salinity adaptation

AbstractDuring adaptation to low salinity (from 20 to 2 ppt), the estuarine clam Rangia cuneata reduces the size of a pool of free amino acids in adductor muscle fibers, presumably to control cell volume. The levels of both free amino acids and ammonia in the blood increase, but the rise in free amino acids is much greater. While free amino acid excretion is never very great, ammonia excretion rises shortly after valve opening and remains high throughout the period of adaptation Evaluation of the convection capability of the cardiovascular system suggests that the rate of free amino acid excretion cannot explain the loss of these substances as such from the tissues. Conversely, the levels of ammonia in blood cannot explain the rate of excretion. We suggest that most of the free amino acids are extruded from the cells and transported to a central site of deamination, from which ammonia is excreted. In situ deamination in the various tissues may occur after the initial stages of low salinity adjustment, but it never appears to explain the major fraction of ammonia excretion.

Age Related Reference Values for Urinary Free Amino Acids: A Simple Method of Evaluation

The urinary excretion of free amino acids has been studied on 339 normal subjects, using ion exchange chromatography. Age related reference values were obtained. A simple method for their evaluation is discussed, and the application of the method to the detection of increased glycinuria, resulting from n-dipropyl acetate therapy, is described.

The production of extracellular amino acids by rumen bacteria

One hundred and sixteen freshly isolated rumen bacteria and 10 laboratory strains were studied for the production and excretion of free amino acids during growth in a basal medium containing glucose, cellobiose, and soluble starch as the energy sources, (NH4)2SO4 as the prime nitrogen source, volatile fatty acids, hemin, vitamins, Na2CO3, and cysteine as the reducing agent. Amino acid analyses of 48-h culture fluids of the isolates indicated the presence of alanine, glutamic acid, valine, aspartic acid, glycine, serine, lysine, methionine, leucine, isoleucine, threonine, histidine, arginine, phenylalanine, and tyrosine. Most isolates excreted some free amino acids. Alanine, glutamic acid, valine, aspartic acid, and glycine were found in the greatest concentrations with some isolates accumulating between 50 and 295 microgram/ml of one or more of these compounds. Concentrations of the remaining amino acids rarely exceeded 20 microgram/ml of culture fluid. Growth studies demonstrated that the amino acids were excreted during active growth of the bacteria and ceased shortly after growth became limited.

The effect of a single oral dose of lysine or arginine on the excretion of free amino acids by the starved laying hen.

Synopsis The excretion of free amino acids by laying hens was measured during the period 0 to 5 h after the oral administration of 0.1 g lysine HCl or 0.1 g arginine HCl. Lysine administration resulted in a significant increase in the excretion (μmoles) of arginine (6.8 to 25.9), ornithine (5.8 to 39.3) and tyrosine (3.2 to 5.1) while arginine administration resulted in a significant increase in the excretion (μmoles) of lysine (6.8 to 93.0), ornithine (4.1 to 71.9), tyrosine (2.3 to 5.5), histidine (10.8 to 88.3), threonine (16.8 to 33.3), serine (22.7 to 34.0) and glycine (17.3 to 56.3). The effect of arginine administration on lysine excretion was significantly greater than that of lysine on arginine excretion (P < 0.01). In the lysine experiment the overall pattern of changes in the hourly excretion rate of the affected amino acids was the same as that of administered lysine. The maximum hourly excretion rate of administered arginine occurred one hour earlier than the maximum for the amino acids affec...

Metabolism of heat-damaged proteins in the rat. influence of heat damage on the excretion of amino acids and peptides in the urine.

1. Freeze-dried cod muscle and casein were subjected to various conditions of heat treat-ment. Diets containing the different products, or the unheated materials, were given to a group of four adult male rats during successive 48 h periods, and urine was collected during the second 24 h of each 48 h period. A further collection of urine was made from the rats after they had been given protein isolated from heated skim-milk powder. The content and amino acid composition of the ‘peptide’ and ‘free amino acids’ in the urines were determined.2. Heat damage to the cod-fillet protein increased the total urinary excretion of peptide-bound amino acids, from 18·6 to 48·8 µmol/rat.d. The composition of the peptide also changed, and in particular there was a marked increase in lysine, from 2·98 to 20·30 µmol %. Three amino acids - lysine, aspartic acid and glutamic acid - together comprised nearly 70 % of the total amino acid residues. There was a corresponding increase in urinary excretion of free amino acids, from 53·7 to I 14·4 µmol/rat.d. The combined losses of lysine in urinary peptide and free amino acids were 1·5 % of the total lysine ingested, as against 0·3 % for the unheated cod fillet.3. The effects of similar heat treatment of casein on the composition of the urinary peptide and free amino acids were less marked. There was no increase in total urinary peptide excretion and there was a smaller increase in the lysine content of the peptide.4. In urine of rats given protein isolated from heated skim-milk powder, the peptide hydro-lysate was rich in lysine and in furosine, which together comprised 41 mol % of the total amino acid composition. These compounds were presumably formed, together with a smaller quantity of pyridosine, from lysine-carbohydrate complex in the urine. It is probable that, as compared with free lysine, the lysine-carbohydrate complex was absorbed relatively in-efficiently from the rat intestine.5. The findings are discussed in relation to the wider question of the metabolism of the ‚unavailable peptide’ that is released in the course of digestion of heat-damaged protein.

Enhanced Excretion of Free Amino Acids by Hyperthyroid Patients

Abstract Greater than normal amounts of one or more amino acids were found in the urines of 20 of 24 thyrotoxic patients. The amino acids most commonly increased were tyrosine (in nine of the 24 patients), β-aminoisobutyric acid (11/24), and cystathionine (12/24); seven patients had concurrent increases in the latter two amino acids. Hyperaminoacidemia, accompanied by generalized hyperaminoaciduria, was seen in the three nonfasting patients whose urine was examined. Sera from patients fasted overnight contained normal concentrations of free amino acids. Urinary calcium exceeded 250 mg/24 h in 10 of the 24 patients; urinary phosphorus exceeded 1.2g/day in four. These variables correlated poorly with each other, with the diagnostic impression of severity, and with the results of thyroid-function tests.

Effect of Vitamin B6 Depletion in Adult Man on the Plasma Concentration and the Urinary Excretion of Free Amino Acids

Effect of Vitamin B6 Depletion in Adult Man on the Plasma Concentration and the Urinary Excretion of Free Amino Acids

Urinary excretion of free amino acids in families and patients with Huntington's chorea

Urinary excretion of free amino acids in families and patients with Huntington's chorea

Excretion of urinary free amino acids in Cushing's syndrome.

ABSTRACT To determine the effect of longterm elevations of plasma adrenocortical hormones on urinary amino acid excretion, the quantities of 18 urinary free amino acids have been determined by means of an automatic amino acid analyzer in 7 patients with Cushing's syndrome. Urine free amino acid determinations were repeated in 3 patients during and after giving 100 rag cortisol for a 1- or 2-day period. Comparison of the 24-hr free amino acid excretion by 12 normal subjects and 7 patients with Cushing's syndrome showed no statistically significant differences in any of the amino acids measured. Administration of cortisol to 3 Cushing's syndrome patients caused an increased excretion of urine free amino acids similar to that reported in cortisol-treated normal subjects. These results suggest that prolonged elevations of plasma nonprotein-bound cortisol alone are not sufficient to produce a sustained increase in amino-aciduria.

Excretion of hydroxyproline and other amino acids in scorbutic guinea-pigs

1. 1. A fall in the urinary excretion of total ( i.e, peptide-bound plus free) amino acids, including hydroxyproline, occuring in scorbutic guinea-pigs and commencing around the 15th day of vitamin deficiency, was also observed in pair-fed controls and is thought, therefore, to be due to inanition. The significance of this finding in relation to the known impairment of collagen synthesis in scurvy is discussed. 2. 2. Although, with the exception of glycine and histidine, the excretion of free amino acids by scorbutic guinea-pigs was comparable to that in normal controls, the excretion in pair-fed controls was reduced. It is suggested, therefore, that scurvy is associated with some degree of general aminoaciduria which offsets the decreased excretion of free amino acids to be exprected as a consequence of the inanition which accompanies the vitamin deficiency in guinea-pigs. 3. 3. An increased excretion of free glycine and histidine observed in scorbutic guinea-pigs is thought to be attributable in part to the general aminoaciduria associated with scurvy and in part to the anomalous excretory response of these two amino acids to inanition. 4. 4. Ammonia excretion was increased 4–10 fold in scorbutic guinea-pigs, and since values in pair-fed controls remained normal, it is considered that the increased excretion in the scorbutic animals is directly attributable to the deficiency of ascorbic acid per se.

Amino Acid Excretion in Alcoholic Cirrhosis.

s1 May 1969Amino Acid Excretion in Alcoholic Cirrhosis.Horace H. Zinneman, M.D., F.A.C.P., Richard P. Doe, M.D., F.A.C.P., Ulysses S. Seal, Ph.D.Horace H. Zinneman, M.D., F.A.C.P.Search for more papers by this author, Richard P. Doe, M.D., F.A.C.P.Search for more papers by this author, Ulysses S. Seal, Ph.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-70-5-1072_2 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptIt appears to be generally accepted that Laënnec's cirrhosis is associated with aminoaciduria. Recent reports by Dent and Knauff tended to place this concept on an insecure basis. Our measurements of free amino acids in plasma and urine were performed by ion-exchange chromatography on columns of Amberlite resin (Spinco aminoacid analyzer). The 24-hr urine excretion of free amino acids was related to the patient's weight. Seven patients were studied during precoma and upon maximal improvement. Contrary to most earlier reports the changes were found to be unspectacular. Plasma concentrations of amino acids proved to be remarkably stable. The urinary excretions... This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAuthors: Horace H. Zinneman, M.D., F.A.C.P.; Richard P. Doe, M.D., F.A.C.P.; Ulysses S. Seal, Ph.D.Affiliations: Minneapolis, Minnesota PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics 1 May 1969Volume 70, Issue 5Page: 1072-1072KeywordsAlcoholicsAmino acidsAttentionBlood plasmaChromatographyCirrhosisExcretionUrine ePublished: 1 December 2008 Issue Published: 1 May 1969 PDF downloadLoading ...

Plasma and urinary amino acids in Laennec's cirrhosis.

Plasma amino acid concentrations and urinary excretion of free amino acids were measured in 7 patients with severe hepatic decompensation (precoma) in Laennec's cirrhosis. Upon maximal improvement these patients served as their own controls. Contrary to earlier reports, the changes were found to be unspectacular. Plasma concentrations of amino acids proved to be remarkably stable. Decreased plasma concentrations of valine, leucine, and isoleucine pointed to a component of steatonecrosis, which was found in liver biopsy specimens and laboratory parameters. The urinary excretion of threonine, serine, asparagine/glutamine, alanine, ethanolamine, and histidine was increased significantly during hepatic decompensation when compared to the excretion values of the same patients at maximal compensation; but even here the changes were within the normal range. General aminoaciduria was observed in 3 cirrhotic patients who had undergone surgical portacaval shunts. It is possible that these changes are a sequence of the surgical procedure.

The content of free and bound amino acids in urine in postoperative periods

In postoperative periods, the output of bound amino acids was found to be increased, while the excretion of free amino acids remained at the preoperational level. The amount of peptides increased, but remained smaller than that of the bound amino acids in the nonampholytic fraction. The quantities of glycine, which is the main constituent of the nonampholytic fraction, fluctuate, being often higher after than before operation.

A study of carbon tetrachloride: VI. Aminoaciduria in response to carbon tetrachloride inhalation

The α-amino acid nitrogen to creatinine nitrogen ratio of normal rats on an ad libitum diet is quite constant and provides a reliable method for determining alterations in amino acid excretion. Exposure of rats to high levels of CCl 4 vapor results in increased urinary excretion of free amino acids. There is a simultaneous increase in the corresponding free amino acids of the blood suggesting that increased urinary excretion is a reflection of elevated levels of free amino acids in the blood. The suggestion is made that the source of the elevated serum free amino acids is damaged tissue and, on the basis of the hepatotoxic action of CCl 4, one would expect damaged liver cells to be the major source of these free amino acids.

EFFECT OF SHORT-TERM THERAPY WITH CORTISOL ON THEURINARY EXCRETION OF FREE AMINO ACIDS.

The effect of short-term cortisol therapy on the urinary excretion of free amino acids was studied in 11 normal humans. Each subject received 100 mg of cortisol daily for a period of 5 days. The quantities of free amino acids in the urine were determined by means of an automatic amino acid analyzer, before, during and after cortisol therapy. The concentration of free amino acids in the plasma was determined parallel with the urine measurements in 4 of the 11 subjects. Of the 25 amino acids which were found and measured in the urine, 10 were not influenced to a significant degree by the administration of cortisol. Fifteen were increased significantly (P <0.01) beyond the pretreatment range. They were threonine, serine, asparagine/glutamine, alanine, histidine, glycine, cystine, phenylalanine, lysine, cystathionine, valine, α-amino-n-butyric acid, leucine and ornithine. The elevated levels of 10 of the amino acids returned to pretreatment levels one day after cessation of cortisol administration. The other ...