Small intestinal absorption of amino acids in scurvy

Saunders, S. J.; Kirsch, Ralph E.

doi:10.1016/0026-0495(68)90109-1

Cited by 7 publications

(9 citation statements)

References 19 publications

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“…In the cell, the com pound may be passed on unchanged, broken down, or used for synthesis. Nevertheless, entry of amino acids is an active process (as is confirmed here by comparison between tables II and III), while exit may be caused by dif fusion [23][24][25]. Other workers have found good correlations between similar in vitro techniques, transport through intestinal loops and clinical situations; for instance, in lactose absorption [27], the effect of hexoses on amino acid uptake [9], and in cystinuria [6,28].…”

Section: Discussionmentioning

confidence: 51%

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The <i>in vitro </i>Uptake of Lysine and Alanine by Human Jejunal Mucosa in Nutritional Rickets

Woodd-Walker¹,

Hansen²,

Saunders³

1973

Ann Nutr Metab

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In some congenital and acquired conditions, aminoaciduria is associated with defective absorption by the mucosa of the small intestine. There is generalised aminoaciduria in nutritional rickets; thus, jejunal function was investigated. Epithelium from six patients was incubated with a dilute solution of radioactively labelled lysine and alanine. The concentration in the tissue, compared with that in the medium, was a measure of the uptake which, in turn, was thought to parallel the absorptive capacity of the gut. In the conditions of these observations, no impairment of uptake was demonstrated.

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Section: Discussionmentioning

confidence: 51%

“…For this reason, we chose the last two for our uptake studies. Alanine is not an essential acid; lysine is, and both are representative, common, and im portant amino acids which have been shown to have independent transport paths [23], The choice of concentrations was arbitrary.…”

Section: Discussionmentioning

confidence: 99%

The <i>in vitro </i>Uptake of Lysine and Alanine by Human Jejunal Mucosa in Nutritional Rickets

Woodd-Walker¹,

Hansen²,

Saunders³

1973

Ann Nutr Metab

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“…Amino acid transport studies also showed a selective inhibition, similar to that observed in carbohydrate transport. At least two of the several active transport systems for amino acids (26,30,34) were impaired in the PAN-treated rats. Glycine, which shares a transport system with iminoacids, and the neutral amino acids, phenylalanine and histidine, showed impaired absorption across the jejunal mucosa.…”

Section: Discussionmentioning

confidence: 93%

Jejunal Transport in Experimental Nephrotic Syndrome

et al. 1983

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SummaryIn vivo jejunal transport of amino acids, monosaccharides, sodium, and electrolytes were studied in rats made nephrotic with puromycin Pmioonucleoside (PAN) and in pair-fed controls. Studies were performed 14 days after a single intravenous dose of PAN when rats were no longer edematous, but were stlll hypoproteinemic. There was decreased absorption of glucose, 31)-methyl glucose, glycine, phenylalanine, histidine, water, and sodium in the nephrotic animals but transport of fructose, lysine and potassium was similar in the nephrotic and control animals. Enzyme kinetic studies for glucose transport showed a mixed type of inhibition affecting both Vm and Km. The jejunal mucosa of nephrotic and control rats had similar ATP content and enzyme activity for Iactase, sucrase, maltase and (Na-K)-ATPase and the ratios of RNA to DNA were similar in the nephrotic and control rats. No abnormality of the jejunum was detected by tight or electron microscopy. The data suggest that the impairment of absorption is a result of decreased activity of jejunal membrane carrier mechanisms. The altered transport may be secondary to effects related to the metabolic consequences of nephrotic syndrome and does not appear to be related to acute purine aminonucleoside toxicity, edema or malnutrition. Abbreviations BUN, blood urea nitrogen PAN, puromycin aminonucleoside PEG, polyethylene glycolThe nephrotic syndrome, characterized by proteinuria, hypoproteinemia, and edema is essentially a protein depletion state (4). An experimental nephrotic model has been available since 1955 when Frenk et al. (9) reported that an aminonucleoside of puromycin, a derivative of the antibiotic puromycin, was capable of regularly producing nephrotic syndrome in rats; nevertheless, few investigations have been carried out on intestinal absorption of nutrients in the nephrotic syndrome. In order to help clarify what effect the ne~hrotic state and its associated metabolic changes might have o i intestinal absorption, we evaluated jejunal transport of nutrients in nephrotic rats 14 days after intravenous treatment with purine aminonucleoside. The results were compared to those of pair-fed controls and indicated a generalized decrease in jejunal absorption in the nephrotic rats. MATERIALS AND METHODSSeventy-four adult male Wistar rats (37), weighing 180-200 g, were randomized into experimental and control groups. The nephrotic syndrome was induced in each animal in the experimental group by intravenous injection of 7.5 mg/100 g body weight of PAN as a 15 mg/ml solution. The controls were given an equal volume of saline. Control rats were pair-fed by being given the same amount of Purina Lab Chow (38) as their nephrotic wunterparts had taken the preceding day. Water intake was allowed ad libitum. Baseline studies were conducted, measuring the daily urine output and the amount of qualitative proteinuria. Intake and weight gain were recorded. Thirteen days after the administration of PAN, 24-h urine protein excretion was quantitated and blood was drawn for se...

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“…The existence of two transport systems for neutral amino acids in mammalian small intestine is generally accepted [3,22,34]. One system has high affinity for neutral amino acids with lipophilic side chains, such as those listed in Table I.…”

Section: Resultsmentioning

confidence: 99%

Amino Acid Transport Pathways in the Small Intestine of the Neonatal Rat

1972

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ExtractThe activity of amino acid transport pathways in the small intestine of the 2-day-old rat was investigated. Transport was determined by measuring the uptake of 1 mM concentrations of various amino acids by intestinal segments after a 5-or 10-min incubation and it was expressed as intracellular accumulation.The neutral amino acid transport pathway was well developed with intracellular accumulation values for leucine, isoleucine, valine, methionine, tryptophan, phenylalanine, tyrosine, and alanine ranging from 3.9-5.6 mM/5 min. The intracellular accumulation of the hydroxy-containing neutral amino acids threonine (essential) and serine (nonessential) were 2.7 mM/5 min, a value significantly lower than those of the other neutral amino acids. The accumulation of histidine was also well below the level for the other neutral amino acids (1.9 mM/5 min). The basic amino acid transport pathway was also operational with accumulation values for lysine, arginine and ornithine ranging from 1.7-2.0 mM/5 min. Accumulation of the essential amino acid lysine was not statistically different from that of nonessential ornithine. Accumulation of aspartic and glutamic acid was only 0.24-0.28 mM/5 min indicating a very low activity of the acidic amino acid transport pathway. Accumulation of sarcosine and betaine was about 0.5 mM/5 min, which indicates a low activity for the imino acid-glycine pathway. The presence of 1 HIM alanine significantly (P < 0.01) increased the accumulation of lysine by 28.5%, which suggests the presence of an exchange transport system. These results show that by operation of the neutral and basic amino acid transport systems, the neonatal rat can effectively absorb all the essential amino acids; however, accumulation of individual amino acids appears to be governed by structural rather than nutritional considerations. SpeculationThe data presented demonstrate the differential ability of the neonatal rat to absorb various ammo acids. This finding is of potential importance in the formulation and evaluation of synthetic protein diets. IntroductionThe quality and quantity of dietary protein which would result in optimal growth and development of infants at a reasonable cost is a subject that has been discussed by nutritionists for several decades. Such discussion stimulated investigation of intestinal transport at, or shortly after birth [4-6, 13, 15, 30].A recent article by the authors [15] characterized the 713

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Small intestinal absorption of amino acids in scurvy

Cited by 7 publications

References 19 publications

The <i>in vitro </i>Uptake of Lysine and Alanine by Human Jejunal Mucosa in Nutritional Rickets

The <i>in vitro </i>Uptake of Lysine and Alanine by Human Jejunal Mucosa in Nutritional Rickets

Jejunal Transport in Experimental Nephrotic Syndrome

Amino Acid Transport Pathways in the Small Intestine of the Neonatal Rat

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