Excretion Of Amino Acids Research Articles

Calciuria and aminoaciduria in very low birth weight infants fed a high-mineral premature formula with varying levels of protein

To assess the influence of protein intake on renal excretion of calcium and amino acids and on bone mineralization in preterm infants, we randomly selected within weight group strata 27 infants who weighed <1500 gm at birth (nine per group) to be fed a high-mineral (calcium, 940 mg/L; phosphorus, 470 mg/L) premature formula with one of the following protein contents: formula A, 3.0 gm/100 kcal; formula B, 2.7 gm/100 kcal; and formula C, 2.2 gm/100 kcal. Mean (±SD) daily weight gain was greater in infants receiving the higher protein intakes for the first 30 days (formula A, 24.8 ± 5.1 gm; formula B, 20.5 ± 3.8 gm; formula C, 16.2 ± 5.9 gm [analysis of variance: p < 0.01; C < A, p <0.05]). Bone mineral content did not differ at any time point, and all groups had a high prevalence of generalized aminoaciduria (4 weeks: formula A, 56%; formula B, 71%; formula C, 75%). Urinary calcium corrected for creatinine (in milligrams per milligram) increased as protein content decreased (2 weeks: formula A, 0.16 ± 0.10; formula B, 0.20 ± 0.13; formula C, 0.44 ± 0.33 [C > A, C > B, p < 0.05]; 4 weeks: formula A, 0.23 ± 0.15; formula B, 0.34 ± 0.17; formula C, 0.49 ± 0.22 [C > A, p < 0.01]). We conclude that the high mineral content and other components of premature formulas result in a higher growth rate and may increase protein requirements. Failure to meet protein requirements may result in underutilization of absorbed calcium and increased renal excretion of calcium. In preterm infants, higher protein intake probably supports rather than jeopardizes bone mineral accretion, and reduces rather then increases calciuria. (J PEDIATR 1994;125:288-94)

The hatching behavior of Echinostoma trivolvis miracidia and their responses to gravity, light and chemicals

Echinostoma trivolvis eggs developed to mature miracidia in both dark and light culture conditions as early as 7 days. Hatching initially occurred in eggs exposed to incandescent light on day 11. Those exposed to fluorescent light first hatched on day 13. Maximum hatching (50+ miracidia/day) lasted only over a 3-day span with the entire hatching period being at the most 5 days. Eggs stored in complete darkness for 21 days developed to mature miracidia in 9 days, and, when exposed to light, gave a 50+ hatch the next day. Those eggs stored for 28 and 35 days developed normally but never hatched upon exposure to light. Miracidia hatched at all times of the day without a circadian pattern. Miracidia that hatched from these trials exhibited a definite negative geotaxis in a four-tube vertical system. This response was either negated in open tubes or dominated by a positive phototaxis in the open-bottomed tubes. In horizontal chambers without the depth component, a strong positive phototaxis was also demonstrated. Miracidia showed a positive klinokinetic response, as determined in phi-chambers, to acidic compounds such as aspartic, glutamic, hydrochloric, sulfuric, and acetic acids. Snail-conditioned water prepared from Helisoma trivolvis snails also elicited a positive response. The neutral amino acid, leucine, and possible snail excretion products, Mg 2+ and ammonia, did not stimulate these echinostrome miracidia.

Systems and mechanisms of amino acid uptake and excretion in prokaryotes

Systems and mechanisms of amino acid uptake and excretion in prokaryotes

Systems and mechanisms of amino acid uptake and excretion in prokaryotes.

Systems and mechanisms of amino acid uptake and excretion in prokaryotes.

The effect of dietary crude protein content on apparent and true ileal nitrogen and amino acid digestibilities

The effect of dietary protein content (25, 60, 95, 130, 165 and 200 g crude protein (N x 6.25)/kg diet) on the apparent and true ileal digestibilities of N and amino acids in meat-and-bone meal given to the growing rat was investigated. Semi-synthetic diets in which meat-and-bone meal was the sole protein source were given to 180 g body-weight rats for 14 d. On the fourteenth day the rats were fed and then killed 4 h after the start of feeding and digesta were sampled from the terminal 200 mm ileum. Endogenous amino acid excretion was determined for eighteen rats given an enzymically hydrolysed casein (EHC)-based diet and with subsequent treatment of the digesta using ultrafiltration. The EHC-fed rats were killed 3 h after the start of feeding and digesta were collected from the terminal 200 mm ileum. True ileal digestibility values determined with references to Cr as a marker were higher than the corresponding apparent estimates. Apparent digestibility values of N and amino acids increased significantly (P < 0.001) with increasing dietary protein level; however, dietary protein content had no significant (P > 0.05) effect on the true ileal digestibilities of N and amino acids. The mean apparent ileal digestibility of N in meat-and-bone meal ranged from 65.6 to 75.3%. The corresponding range for the true ileal digestibility of N was 76.9 to 78.2%. True ileal digestibility, unlike apparent digestibility, appears to be independent of dietary protein level and may allow feed ingredients to be compared accurately even if they are ingested in different quantities.

The differential diagnostic value of urinary enzyme and amino acid excretion in children with nephrotic syndrome.

Urinary enzymes N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyl transpeptidase (gamma-GT) are sensitive markers of specific renal cell damage. Excessive urinary amino acid excretion may also be an indicator of renal tubular damage. We have evaluated urinary excretion of NAG, gamma-GT and 37 amino acids, phospholipids and dipeptides in 30 children (aged 2.3-18.1 years) with nephrotic syndrome (NS), 23 with minimal change nephrotic syndrome (MCNS), 7 with focal segmental glomerulosclerosis (FSGS) and 16 healthy age-matched controls. Nine MCNS patients were in relapse and 14 in remission. Enzyme activity is expressed as micromoles per milligram urinary creatinine. In FSGS, NAG excretion correlated with the following: blood urea nitrogen (BUN) (r = 0.8), serum protein (r = 0.57), serum cholesterol (r = 0.85), serum albumin (r = -0.68) and proteinuria (r = 0.56). In FSGS the gamma-GT excretion was not significantly different from MCNS in remission or in relapse. In FSGS, gamma-GT excretion correlated with the following: BUN (r = 0.48), serum creatinine (r = -0.66), serum protein (r = -0.54), serum albumin (r = -0.68) and serum cholesterol (r = 0.87). Compared with controls, the urinary excretion of 5 amino acids was increased in FSGS patients as a possible indicator of tubular damage. The value for 7 amino acids was reduced in MCNS patients. Urinary amino acid excretion was not different from controls for the other amino acids in either FSGS or MCNS.(ABSTRACT TRUNCATED AT 250 WORDS)

2H- and13C-labeled amino acids generated by obligate methylotrophs Biosynthesis and MS monitoring

Biosynthetic preparation of(2)H- and(13)C- labeled amino acids was studied using a leucine-producing mutant of the obligate methylotroph,Methylobacillus flagellatum. The strain was cultivated in various media containing(13)C- or(2)H-analogs of methanol. The total protein from each experiment was subjected to acid hydrolysis and converted into a mixture of dansyl amino acid methyl esters. The samples of excreted leucine were converted into methyl esters of dansyl and benzyloxycarbonyl derivatives. Electron impact mass spectrometry was performed to detect stable isotope enrichment of the amino acids. According to the mass spectrometric analysis it is feasible to use methylotrophic microorganisms for the preparation of(2)H- and(13)C- analogs of amino acids by labeled methanol bioconversion; the excreted amino acids can be convenient for express analysis as an indicator of isotopic enrichment of the total protein. The data obtained testified to a high efficiency of dansyl derivatization for mass spectrometric analysis of complex amino acid mixtures.

Amino acid losses in ileostomy fluid on a protein-free diet

The contribution of losses via the gastrointestinal tract to maintenance amino acid requirements was assessed by collecting the ileostomy fluid of volunteers given a protein-free diet for 5 d. The subjects were eight adult men and women with terminal ileum ileostomies after ulcerative colitis. Four consecutive 24-h collections of both digesta and urine were made. On the last 2 d an antibiotic was given that suppressed microbial activity in the digesta and slightly reduced ileostomy outflow. Mean daily amino acid excretion in ileostomy fluid ranged from 32 mg/d for methionine to approximately 330 mg/d for aspartate and glutamate. These losses were compared with current international estimates of amino acid requirements. For most essential amino acids gastrointestinal losses accounted for 14-33% of daily maintenance requirements but for threonine the contribution was 61%.

Glycine Loading and Urinary Oxalate Excretion

One metabolic pathway for glycine leads to glyoxylate which is the precursor of oxalate. To investigate whether absorption of glycine solution in transurethral operations may promote precipitation of calcium oxalate stones, we collected urine for 24 h before and after an intravenous infusion of 22 g of glycine in 10 male volunteers. There were no significant changes in the urinary excretion of oxalate, calcium, or citrate. Urine volume and amino acid excretion increased, while the urine contained less potassium. These results provide no biochemical evidence of an increased risk of renal lithiasis due to glycine irrigation during transurethral operations.

Renal ammonia and glutamine metabolism during liver insufficiency-induced hyperammonemia in the rat.

Renal glutamine uptake and subsequent urinary ammonia excretion could be an important alternative pathway of ammonia disposal from the body during liver failure (diminished urea synthesis), but this pathway has received little attention. Therefore, we investigated renal glutamine and ammonia metabolism in midly hyperammonemic, portacaval shunted rats and severely hyperammonemic rats with acute liver ischemia compared to their respective controls, to investigate whether renal ammonia disposal from the body is enhanced during hyperammonemia and to explore the limits of the pathway. Renal fluxes, urinary excretion, and renal tissue concentrations of amino acids and ammonia were measured 24 h after portacaval shunting, and 2, 4, and 6 h after liver ischemia induction and in the appropriate controls. Arterial ammonia increased to 247 +/- 22 microM after portacaval shunting compared to controls (51 +/- 8 microM) (P < 0.001) and increased to 934 +/- 54 microM during liver ischemia (P < 0.001). Arterial glutamine increased to 697 +/- 93 microM after portacaval shunting compared to controls (513 +/- 40 microM) (P < 0.01) and further increased to 3781 +/- 248 microM during liver ischemia (P < 0.001). In contrast to controls, in portacaval shunted rats the kidney net disposed ammonia from the body by diminishing renal venous ammonia release (from 267 +/- 33 to -49 +/- 59 nmol/100 g body wt per min) and enhancing urinary ammonia excretion from 113 +/- 24 to 305 +/- 52 nmol/100 g body wt per min (both P < 0.01). Renal glutamine uptake diminished in portacaval shunted rats compared to controls (-107 +/- 33 vs. -322 +/- 41 nmol/100 g body wt per min) (P < 0.01). However, during liver ischemia, net renal ammonia disposal from the body did not further increase (294 +/- 88 vs. 144 +/- 101 nmol/100 g body wt per min during portacaval shunting versus liver ischemia). Renal glutamine uptake was comparable in both hyperammonemic models. These results indicate that the rat kidney plays an important role in ammonia disposal during mild hyperammonemia. However, during severe liver insufficiency induced-hyperammonemia, ammonia disposal capacity appears to be exceeded.

Dietary Fiber Viscosity and Endogenous Protein Excretion at the Terminal Ileum of Growing Rats

The effect of dietary fiber viscosity on the excretion of endogenous nitrogen and amino acids from the small intestinal lumen of growing rats was investigated. Rats were fed for 12 d protein-free diets containing 5% cellulose (negligible viscosity) or 5% carboxymethylcellulose of low (20 cP), medium (800 cP) or high (2000 cP) viscosity, as the sole dietary fiber source. As dietary fiber viscosity increased from 0 to 2000 cP, there was a significant (P < 0.05) linear increase in the flow of endogenous nitrogen, aspartic acid, serine, glutamic acid, proline, threonine, glycine, alanine, isoleucine, histidine, valine, methionine, leucine and lysine at the terminal ileum. The amino acid composition of the ileal digesta was unaffected by changes in fiber viscosity. It seems that either endogenous protein of a similar origin was secreted in larger amounts or that the digestion and absorption of endogenous amino acids was inhibited as dietary fiber viscosity increased. There was a significant (P < 0.05) linear increase in the concentration of sialic acids relative to chromic oxide in the small intestinal contents with increasing fiber viscosity, indicating an increase in mucoproteins.

Research Note: Effect of Crystalline Lysine and Methionine Intake on Amino Acid Excretion by Precision-Fed Cockerels

A study was conducted to investigate the relationship between increasing intake of crystalline lysine and methionine and excretion of these amino acids in a precision-fed cockerel assay. Birds were deprived of feed for 24h and then given increasing amounts of crystalline L-Lysine-HCl or DL-methionine via crop intubation. The amino acids were given with either 30 g of sucrose or with 30 g of an intact protein diet deficient in the test amino acid. The supplemental dietary levels (percentage of diet) were 0, 1.0, 2.4, and 9.1% for lysine and 0, .2, .45, 1.6, and 7.1% for methionine. Excreta (feces plus urine) were quantitatively collected for 48h postfeeding. The results showed that lysine and methionine excretion were significantly increased (P < .05) only at the highest dietary level. The effect of supplemental dietary lysine on lysine excretion was greater for the sucrose diet than the intact protein diet. Relative lysine balance (intake minus excretion expressed as a percentage of intake) decreased at the 2.4 and 9.1% levels in the sucrose diet and at the 9.1% level in the intact protein diet. Relative methionine balance was high at all intake levels. The results of the present study indicate that crop intubation of moderate levels of crystalline amino acids has little or no effect on amino acid excretion in the precision-fed cockerel assay.

Prospective analysis and classification of patients with cystinuria identified in a newborn screening program

Patients who inherit mutant cystinuria genes excrete high concentrations of cystine, ornithine, arginine, and lysine in the urine. At least three variants of cystinuria can be distinguished in heterozygotes. To determine whether certain combinations of mutant genes are more disadvantageous than others, we analyzed amino acid excretion in families of 17 probands with cystinuria identified by the Quebec neonatal screening program. Parents of the probands were classified into the three known phenotypes by calculating the sum of cystine, ornithine, arginine, and lysine excretion. Although parents of type I/I homozygotes excreted amounts of cystine in the normal range, their offspring excreted significantly greater amounts of urinary cystine than did children who have type I/III genetic compounds. This observation suggests that types I and III cystinuria mutations might involve two distinct genetic loci. Children with type I/I homozygous cystinuria often excrete cystine at levels greater than the theoretic solubility limit and may be at greatest risk for nephrolithiasis. We outline an approach to monitoring children with cystinuria who come to medical attention before formation of cystine stones.

Urinary excretion of amino acids in normal and cystinuric dogs

The 24-h urine excretion of 20 amino acids was investigated in 24 cystinuric and 15 normal dogs. The diagnosis of cystinuria was based on infrared spectroscopy of removed uroliths, which in all cases were composed of pure cystine. Seven of 24 cystinuric dogs showed normal cystine excretion compared to normal dogs, and four of 24 dogs showed normal total amino acid excretion. In contrast to earlier investigations, almost half of the cystinuric dogs (46%) showed elevated excretion of five or more amino acids. Isolated cystinuria, or isolated dibasic amino aciduria was not found. Compared to normal dogs, the cystinuric dogs showed a significantly (P < 0.05) increased excretion of cystine, arginine, lysine, cystathionine, glutamic acid, threonine and glutamine. There was a significant correlation (P < 0.05) between the urinary excretion of cystine and 10 other amino acids, with the highest correlation found (P < 0.001) for arginine, lysine, cystathionine, ornithine and 1-methyl-histidine. Three patterns of amino acid excretion could be identified: (1) increased excretion and a significant correlation with cystine for the three dibasic amino acids (lysine, arginine and ornithine), compatible with a common reabsorption mechanism as shown in man. This pattern was also found for cystathionine and glutamic acid, which might indicate a relation in metabolism or transport; (2) increased excretion but no correlation with cystine for glutamine, threonine and citrulline; (3) good correlation with cystine, but no increased excretion for 1-methyl-histidine, phenylalanine, 3-methyl-histidine, leucine and alanine. The great variation in urinary cystine excretion suggests that factors other than the excretion of cystine must be considered as causes of cystine urolith formation. For example, cystinuric dogs were found to have lower diuresis than normal dogs and produced urine with higher cystine concentration thereby increasing the risk of cystine urolith formation.

The effect of food dry matter intake on endogenous ileal amino acid excretion determined under peptide alimentation in the 50 kg liveweight pig

AbstractThe daily ileal excretion of amino acids was measured at different food dry matter intakes for the 50 kg liveweight pig under conditions of peptide alimentation. The experiment comprised two cross‐over design trials each involving four pairs of entire male pigs fitted with simple T‐cannulae at the terminal ileum and fed a hydrolysed casein semi‐synthetic diet. Each pair of pigs received one of four sequences of food dry matter intake arranged in a Latin square design, namely 0.06, 0.08, 0.10 and 0.12 (Trial 1) and 0.05, 0.07, 0.09 and 0.11 (Trial 2) of metabolic body weight (W0.75) day−1. Each pig received the diet at its described level of intake for 8 days, with continuous 24 h collection of ileal digesta on the fifth and eighth days. Chromic oxide was included in the diet to permit correction of ileal flows to complete digesta collection. Pooled digesta from each pig at each level of dry matter intake were centrifuged and ultrafiltered and the high‐molecular‐weight fraction was analysed for amino acid and nitrogen contents. There were significant (P &lt; 0.05) linear relationships between endogenous ileal amino acid, nitrogen and dry matter excretion (mg day−1) and food dry matter intake (g day−1) except for lysine, glutamic acid and phenylalanine which increased in a curvilinear manner (P &lt; 0.05). The results indicate that dietary dry matter intake influences endogenous excretion from the ileum. The relationships, determined under physiological conditions, provide preliminary data on the magnitude of small intestinal amino acid loss in the young growing pig.

Endogenous lysine and other amino acid flows at the terminal ileum of the growing pig (20 kg bodyweight): The effect of protein‐free, synthetic amino acid, peptide and protein alimentation

AbstractTwenty‐four crossbred pigs of 15 kg initial bodyweight were fed four semi‐synthetic diets for 10 days according to a completely randomised design. The study aimed to determine the effects of state of body nitrogen balance and the presence of dietary peptides and protein in the digestive tract on the excretion of endogenous amino acids from the ileum of the pig. Endogenous lysine excretion was determined for pigs given a protein‐free (PF) diet, an enzymically hydrolysed casein‐ (EHC), a zein‐ (ZN) or a synthetic amino acid‐ (SAA) based diet. Digesta from the EHC‐fed animals were centrifuged and ultrafiltered after collection and the precipitate plus retentate fraction was used to determine the endogenous flows. Such processing excludes unabsorbed dietary amino acids from the measure of endogenous loss. ZN is naturally deficient in lysine and tryptophan and these two amino acids were omitted from the synthetic amino acid‐based diet to allow direct measurement of endogenous lysine flow. Pigs given the ZN and SAA diets received free lysine and tryptophan orally throughout the study except for the final 2 days of the study, when these amino acids were infused intravenously. Endogenous flows for amino acids other than lysine were determined for pigs given the PF and EHC diets. On the final day of the study the pigs were given their daily dietary allowance hourly and killed 10 h after the start of feeding. Digesta were collected from the terminal ileum (20 cm anterior to the ileo‐caecal junction) and endogenous flows were determined by reference to the marker chromic oxide. The mean endogenous ileal lysine flows for the ZN‐ and EHC‐fed pigs were not significantly different (overall mean, 419 mg kg−1 dry matter intake), but were higher (P &lt; 0.05) than those for the PF‐ and SAA‐fed pigs (overall mean, 268 mg kg−1 dry matter intake) whose mean flows were not significantly different from each other. The mean endogenous ileal flows for amino acids other than lysine were higher (P &lt; 0.05) for the EHC‐fed pigs compared to the animals on the PF diet, except for proline, glycine and arginine. The similar endogenous ileal lysine excretion for pigs receiving a SAA‐based diet and in positive body nitrogen balance, and PF‐fed pigs in negative body nitrogen balance, indicates that negative body nitrogen balance per se does not lead to a lowered endogenous ileal excretion. It would appear, however, that the presence of dietary peptides or protein in the gut increases amino acid excretion at the terminal ileum above that found with PF or SAA alimentation. Consequently, endogenous ileal amino acid flow in the pig may be underestimated when determined by the traditional PF method.

Aminino acid profiles in dogs with chronic renal failure fed two diets

Summary Amino acid profiles and serum albumin and serum total protein concentrations were evaluated in dogs with renal disease. Nine dogs ranging in age from 1 to 15 years were identified as having mild to moderate chronic renal failure (crf; exogenous creatinine clearance, 0.5 to 2.13 ml/kg of body weight/min). These dogs and a group of 10 clinically normal control dogs, were fed a diet containing 31% protein for 8 weeks, at which time serum and urine imino acid assays and clearance studies were performed. All dogs then were fed a diet containing 16% protein for 3 weeks and then reevaluated. Chronic renal failure was associated with mild abnormalities in serum concentrations of amino acids. When fed the higher protein diet, dogs with crf had lower serum concentrations of glutamine, leucine, proline, and serine and higher serum concentrations of cystathionine and 3-methylhistidine than clinically normal control dogs. When fed the low protein diet, dogs with crf had lower serum serine concentrations and higher serum concentrations of cystathionine, phenylalanine, and 3-methylhistidine. Urine excretion of amino acids in all dogs on both diets was low, and dogs with crf had lower renal clearances of 3-methylhistidine than control dogs. There were no significant differences in concentrations of serum albumin and total solids between either group, regardless of diet. We concluded that dogs with mild to moderately severe crf have mild abnormalities of serum free amino acid concentrations, but renal conservation of essential amino acids is not impaired.

Effects of the [formula omitted] regulatory locus on biosynthesis and excretion of amino acids in [formula omitted

We have partially characterized phenotypic effects of an unusual amino acid regulatory locus, flrA , in E. coli B r that alters the expression of the ilv and leu operons [ Kline, E.L (1972) J. Bacteriol. 110:1127–1134]. This study demonstrated that a primary effect of the flrA 7 mutation in haploid strains was overproduction of valine. In diploid strains ( F′ flrA+ flrA7 ) this mutation resulted in excretion of valine, isoleucine, leucine, aspartate, threonine, glutamate, histidine and lysine. Increased excretion of amino acids by mutant strains might be explained by a membrane alteration or by flrA encoding a positive regulatory factor that affects the ilv operon and has pleiotropic effects on other amino acid operons.

Isolation of auxotrophic mutants from acetobacter methanolicus MB 58

AbstractThe lysine content of the biomass of the acidophilic facultatively methylotrophic bacterium Acetobacter methanolicus MB 58 was increased by genetic manipulations.A homoserine auxotroph, MB 58.196, and a threonine auxotroph, MB 58.195, were obtained from Acetobacter methanolicus MB 58 by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine treatment.Investigations of enzyme activities revealed that the homoserine auxotroph lacks homoserine dehydrogenase activity, and the threonine auxotroph lacks homoserine kinase activity.Concerning the lysine‐producing ability, only the homoserine auxotrophic mutant accumulates lysine in the intracellular pool. The intracellular lysine content of this mutant was increased 40‐fold.An excretion of amino acids into the medium was not detected. A homoserine resistant mutant, MB 58.196.10, isolated from MB 58.196 by UV‐irradiation, was able to excrete lysine. About 95% of free lysine were found in the culture medium. Altogether, the free lysine concentration was increased 800‐fold in comparison to the wild‐type strain.By these genetic manipulations the total lysine concentration of MB 58.196 was increased to 2.7% and of MB 58.196.10 to 56% in comparison to the wild‐type strain.

Tubular handling of amino acids after intravenous infusion of amino acids in healthy humans

To examine the fractional excretion of amino acids after an increase in the filtered load, and to study a possible coupling between proximal tubular reabsorption of individual amino acids and sodium/water, eleven healthy subjects were examined before and during intravenous infusion of a mixture of essential and non-essential amino acids. Thirteen healthy subjects, who received isotonic glucose instead, participated in an identical time-control study. Glomerular filtration rate (GFR), renal plasma flow (RPF), and proximal and distal absolute and fractional tubular reabsorption of sodium and water (PARNa, PFRNa/water, DARNa, and DFRNa) evaluated by the lithium clearance method were determined during four clearance periods of 30 min each. After amino acid infusion, GFR and RPF increased, whereas filtration fraction (FF) was unchanged. PARNa was unchanged, but lithium clearance increased significantly (P less than 0.05) and PFRNa/water fell, indicating an increased delivery of sodium and water out of the proximal tubules. DARNa increased, but DFRNa was unchanged, thus no net increase was recorded in urinary sodium and water output. In the time-control study, no changes in kidney function were seen. Absolute excretion of amino acids increased for glutamic acid, serine, glutamine, glycine, threonine, histidine, alanine, arginine, tyrosine, valine, methionine, isoleucine, phenylalanine, leucine, and lysine (P less than 0.01), and fractional excretion increased for all but glutamic acid, tyrosine, arginine, isoleucine, and leucine. Reabsorption of amino acids was enhanced uniformly and almost paralleled the filtered load without any sign of saturation of the reabsorption mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)