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PubMed1977

Amino acid metabolism of dog jejunum before and during absorption of keto analogues.

In fasting dogs, significant uptake by the jejunal wall from arterial blood was found for glutamine and eight other amino acids. Significant release into the mesenteric vein of ammonium, alanine, citrulline, and proline occurred, equal in nitrogen content to glutamine nitrogen taken up. The keto analogues of leucine, valine, and isoleucine, infused for 1 h into the lumen at initial concentrations of 10mM, disappeared from the lumen at 20.2 +/- 1.6, 18.6 +/- 2.0, and 15.7 +/- 2.8 mumol/cm in 1h, respectively. Eight fifteen and seventeen percent, respectively, of these absorbed quantities were released into mesenteric blood as leucine, valine, and isoleucine plus alloisoleucine, indicating significant amination of the keto acids by the gut wall. No significant changes were detected in the arteriovenous differences of any other amino acids or ammonium. The remainder of the absorbed analogues of valine and isoleucine appeared as such in the blood. In the case of the keto analogue of leucine, there was apparent degradation by the gut wall of 34% of the absorbed compound.

Amino Acids↗
PubMed1989

[The effect of enriched branched chain amino acid solution on amino acid metabolism during perioperative total parenteral nutrition support].

A prospective, randomized clinical study was performed in patients underwent subtotal gastrectomy or hemicolectomy. Patients were randomly divided into two groups receiving standard amino acid solution (23% BCAA) or a solution enriched with branched chain amino acid (41% BCAA). Preoperative postprandial plasma amino acid levels were used as base line. The amino acid concentrations in plasma between control group (A) and study group (B) were compared during perioperative period. The dynamics of postoperative plasma amino acid profile of the two groups were similar except that plasma BCAA concentrations were very high in group B. In both groups, the levels of plasma glutamine, alanine, tyrosine, lysine, threonine, arginine, asparagine, and cystine decreased, whereas the levels of plasma methionine, phenylalanine, and tryptophan increased. The solution of 41% BCAA was not found to be superior to standard 23% BCAA in normalizing the disorder of plasma amino acid spectrum during the period of TPN support. The differences of urinary amino acid excretion including 3-MHIS and nitrogen balance between the two groups were not statistically significant. Also the results showed more severe disorder of plasma amino acid profile caused by 41% BCAA solution than by standard solution of 23% BCAA.

Adult↗
PubMed1983

Action of Inhibitors of Ammonia Assimilation on Amino Acid Metabolism in Hordeum vulgare L. (cv Golden Promise).

Barley (Hordeum vulgare L. cv Golden Promise) plants were grown in a continuous culture system in which the root and shoot ammonia and amino acid levels were constant over a 6-hour experimental period. Methionine sulfoximine (MSO), 1 millimolarity when added to the culture medium, caused a total inactivation of root glutamine synthetase with little effect on the shoot enzyme. Root ammonia levels increased and glutamine levels decreased, irrespective of whether the plants were grown in 1 millimolar nitrate or 1 millimolar ammonia. Levels of glutamate, aspartate, serine, threonine, and asparagine all increased. There was little alteration in the amino acid and ammonia levels in the shoot, suggesting that MSO is not rapidly transported.The addition of azaserine (25 micrograms per milliliter) to nitrate-grown plants caused a rapid increase in root ammonia, glutamine, and serine levels with a corresponding decrease in glutamate, aspartate, and alanine. Glutamine levels also increased in the shoot.The in vivo effect of MSO and azaserine was as would be predicted by their known in vitro inhibitory action if the glutamine synthetase/glutamate synthase pathway of ammonia assimilation was in operation.

Journal Article↗
PubMed1982

Some aspects on amino acid metabolism in relation to glucose and ketone bodies in brain cortex slices of the rat.

Glucose is the major fuel of the adult brain under normal conditions. The most abundant free amino acids of the brain are: Glutamate, taurine N-acetylaspartate, glutamine, aspartate and 4-aminobutyrate. Deprivation of glucose from the incubation medium of brain cortex slices decreases mainly glutamate and glutamine content. Substitution of pyruvate for glucose maintains the content of aspartate and glutamate but not of glutamine. Therefore the entire glucose molecule is indispensable for the maintenance of the glutamine content. When branched chain amino acids, (BCAA), leucine, isoleucine and valine (0.5 mM) are added to the incubation medium in the presence of glucose the content of glutamine only is increased, all other amino acids are decreased. This suggests that BCAA spare protein as in muscle and produce glutamine. Branched chain amino acids in the presence of pyruvate do not spare protein but they still produce glutamine. Furthermore it seems that they potentiate the protein sparing effect of glucose in brain. In all these experiments glutamate and aspartate content in the incubation medium ranges from 3-10% of their total content (tissue plus media). On the other hand 40-60% of each of the other amino acids is found outside. The presence of 3-hydroxybutyrate and glucose in the incubation medium of brain cortex slices from normal rats spares protein but can maintain constant the content of glutamate, aspartate and glutamine. In addition 3-hydroxybutyrate blocks the release into the medium of glutamate and aspartate.

3-Hydroxybutyric Acid↗