Amino Acids In Arterial Plasma Research Articles

The effect of fractionated plasma separation and adsorption on cerebral amino acid metabolism and oxidative metabolism during acute liver failure

Patients with acute liver failure have a disturbed amino acid metabolism and a compromised oxidative metabolism in the brain. A limited number of clinically neuroprotective interventions are available. This study aimed at assessing the effect of fractionated plasma separation and adsorption (FPSA), an extracorporeal liver support system, on cerebral amino acids and lactate to pyruvate ratio. Seven patients with acute liver failure and high risk of intracranial hypertension were included for cerebral microdialysis and intracranial pressure monitoring. Microdialysate, arterial blood, and venous blood from the jugular bulb were sampled, before and after an FPSA session, and the content of nineteen amino acids, lactate, and pyruvate was determined. The total amino acid concentration in arterial plasma was not significantly reduced by FPSA (11.2 mM (3.0-26.0 mM) vs. 9.7 mM (2.7-13.6 mM); median with range). The total amino acid content in the microdialysate was 5.6 mM both before and after FPSA and no change in glutamine content was observed in plasma or microdialysate. The content of aromatic amino acids in arterial plasma, but not in microdialysate, was marginally reduced (p<0.05). Arterial lactate concentration and lactate to pyruvate ratio in the microdialysate did not change following FPSA. One single treatment session with FPSA had a marginal effect on plasma amino acid composition. We found minimal changes in the amino acids content in the microdialysate, and the lactate to pyruvate ratio was unaffected.

Appearance of Individual Amino Acid Concentrations in Arterial Blood During Steady‐State Infusions of Different Amino Acid Formulations to ICU Patients in Support of Whole‐Body Protein Metabolism

Previous work has demonstrated a relationship between arterial amino acid concentrations and uptake of amino acids across peripheral tissues in healthy volunteers, as well as in chronically and acutely ill patients. The aim of the present study was to evaluate whether different amino acid profiles in commercially available amino acid formulations are translated into significantly different arterial amino acid concentrations presumably high enough to promote protein metabolism in intensive care unit (ICU) patients. Nonprotein calories (60% glucose: 40% lipid) were simultaneously and constantly infused over 72 hours. Different free amino acid solutions were infused at random to each patient for 24 hours in order to determine the appearance of steady-state arterial concentrations of individual amino acids. Basal metabolic and nutrition states were defined after a 12-hour infusion period with glucose in each patient. Healthy volunteers receiving a standardized oral meal served as reference subjects in measurements of venous amino acid concentrations after normal oral food intake. The sum of all amino acids in arterial plasma increased significantly during steady-state infusions of all the free amino acid solutions vs basal state in ICU patients. Only glutamine, taurine, and tyrosine did not increase at all vs basal state during steady-state infusions of the 3 formulations. Alanine, arginine, citrulline, glycine, histidine, serine, methionine, phenylalanine, valine, and ornithine showed different concentration among the amino acid solutions during infusions. Healthy volunteers had significantly higher overall concentrations of amino acids in both fasted and fed state compared with ICU patients, which indicates that free amino acid solutions remain a limiting component in artificial nutrition to patients to promote arterial amino acid concentrations in the artificially fed state. It appears important to continue further improvement of composition profile in solutions of free amino acids to promote adequate uptake across organ beds in promotion of protein balance in artificially nourished patients.

Quantitative measurement of cerebral protein synthesis in vivo: theory and methodological considerations

The true rate of cerebral protein synthesis can be calculated from the ratio of labeled proteins to integrated arterial plasma amino acid specific activity (SA) only when the fraction of amino acid precursor pool dilution is known. In the following, current experimental designs on the measurement of cerebral protein synthesis are discussed and compared to our own approach in which the determination of regional precursor pool dilution by recycled unlabeled leucine is combined with the quantitation of regional cerebral protein synthesis rates. For this purpose, a constant arterial plasma leucine SA level is maintained for 45 min by programmed intravenous infusion which is sufficient for complete equilibrium between tissue leucine pool SAs and plasma free leucine SA. In addition to the regional assessment of the precursor dilution factor, protein radioactivity can be determined in the same tissue sample or in parallel brain sections of the same animal by quantitative autoradiography. It is then possible to calculate the actual rate of protein synthesis using the correct fraction of precursor pool dilution. This renders our approach particularly suitable for the quantitative measurement of regional CPS under pathological conditions.

Splanchnic-bed transfers of amino acids in sheep blood and plasma, as monitored through use of a multiple U-13C-labelled amino acid mixture

AbstractThe response in whole-body and splanchnic tissue mass and isotope amino acid transfers in both plasma and blood has been studied in sheep offered 800 g lucerne (Medicago sutiva) pellets/d. Amino acid mass transfers were quantified over a 4 h period,by arterio-venous procedures, across the portal-drained viscera (PDV) and liver on day 5 of an intravenous infusion of either vehicle or the methylated products, choline (0.5 g/d) plus creatine (10 g/d). Isotopic movements were monitored over the same period during a 10 h infusion of a mixture of U-13C-labelled amino acids obtained from hydrolysis of labelled algal cells. Sixteen amino acids were monitored by gas chromatography-mass spectrometry, with thirteen of these analysed within a single chromatographic analysis. Except for methionine, which is discussed in a previous paper, no significant effects of choline plus creatine infusion were observed on any of the variables reported. Whole-body protein irreversible-loss rates ranged from 158 to 245 g/d for the essential amino acids, based on the relative enrichments (dilution of the U-13C molecules by those unlabelled) of free amino acids in arterial plasma, and 206-519 g/d, when blood free amino acid relative enrichments were used for the calculations. Closer agreement was obtained between lysine, threonine, phenylalanine and the branched-chain amino acids. Plasma relative enrichments always exceeded those in blood (P &lt; 0.001), possibly due to hydrolysis of peptides or degradation of protein within the erythrocyte or slow equilibration between plasma and the erythrocyte. Net absorbed amino acids across the PDV were carried predominantly in the plasma. Little evidence was obtained of any major and general involvement of the erythrocytes in the transport of free amino acids from the liver. Net isotope movements also supported these findings. Estimates of protein synthesis rates across the PDV tissues from [U-13C] leucine kinetics showed good agreement with previous values obtained with single-labelled leucine. Variable rates were obtained between the essential amino acids, probably due to different intracellular dilutions. Isotope dilution across the liver was small and could be attributed predominantly to uni-directional transfer from extracellular sources into the hepatocytes and this probably dominates the turnover of the intracellular hepatic amino acid pools.

Arterial plasma amino acid patterns in patients with cirrhosis, and after liver-transplantation: [formula omitted] Dept. of Gastroenterology and Dept. of Cardiology(∗), Medizinische Hochschule Hannover, D-30623 Hannover, Germany

Arterial plasma amino acid patterns in patients with cirrhosis, and after liver-transplantation: [formula omitted] Dept. of Gastroenterology and Dept. of Cardiology(∗), Medizinische Hochschule Hannover, D-30623 Hannover, Germany

Effect of mimosine on portal-drained visceral net flux and concentrations of amino acids and minerals in plasma of Alpine goats

This experiment was designed to investigate whether circulating mimosine imposes limitations on absorption of amino acids and minerals from the gastrointestinal tract of Alpine goats. Circulating mimosine, portal blood and plasma flow rate, and concentrations and net absorption of amino acids and minerals were measured 60 h before (PRE) and 24 h after (POST) the femoral vein infusion of mimosine (12.5 mg kg −1 BW −0.75 h −1). Mimosine infusion did not affect portal plasma flow rate. Venous and arterial plasma amino acid and mineral concentrations were depressed and the absorption of alanine ( P < 0.09), serine ( P < 0.04) and methionine ( P < 0.03) from the gastrointestinal tract were reduced for up to 24 h after the cessation of mimosine infusion, even when normal feeding was resumed. This disruption was possibly caused by the circulating mimosine (4.88 μm 1 −1 during POST) directly, via chelation or competition for absorption, or, indirectly, by gastrointestinal lesions resulting from circulating mimosine. Pivotal to this experiment was the observation that mimosine was eliminated from the goat circulatory system approximately 40 times more rapidly in a 24 h period than when similar concentrations were infused in sheep.

Plasma amino acid concentration changes during total parental nutrition in critically ill patients

In 16 critically ill patients with full-blown stress reaction and without severe organ failure, we studied the kinetics of the arterial plasma amino acid (aa) profile during the first 48 h of total parenteral nutrition (TPN) in order to assess the time necessary to reach the steady-state condition during infusion. Each patient was treated with one of three different amino acid solutions giving, with the same nitrogen load, different intakes of individual amino acids. We found four different responses to the administered amino acids. 1. (a) An increase in plasma levels within 1 h from the start of the TPN, with no further variation during the study period. 2. (b) The same trend with a steady-state obtained after 6–24 h of TPN infusion. 3. (c) No influence at all. 4. (d) A decrease from fasting plasma levels with a steady-state attained at various times during the study period. Some amino acids showed a different trend depending on the dose given. At lower doses a steady state was achieved sooner. Plasma levels of amino acids not supplied in the TPN were unaffected or decreased, achieving a steady state at various times during the study period. We conclude that, in critically ill patients, stable arterial plasma amino acid concentrations are obtained within 24 h of starting TPN. In such patients, valid studies of the effect of amino acid solutions may therefore be carried out over short periods of time, thereby minimizing errors due to a fluctuating and unstable clinical state.

The influence of epidural analgesia on the splanchnic exchange of amino acids during upper abdominal surgery.

Splanchnic turnover of plasma amino acids was studied in 10 patients given thoracic epidural analgesia combined with general anaesthesia for elective cholecystectomy. Ten other patients given only general anaesthesia for cholecystectomy served as a control group. All patients received an infusion of glucose during the investigation. The total concentration of amino acids in arterial plasma did not change in the patients given epidural analgesia but decreased by approximately 15% in the non-epidural group. In both groups splanchnic uptake of amino acids increased during surgery and was found to be more than doubled in the early postoperative period. The addition of epidural analgesia to general anaesthesia did not modify the splanchnic uptake of amino acids during surgery and in the immediate (2 h) postoperative period.

Arterial Plasma Amino Acids during the First Week following Femoral Shaft Fracture

In ten patients with a femoral shaft fracture, arterial plasma amino acids and glucagon, blood glucose, and serum insulin were measured after an overnight fast on the third, fifth, and seventh days following injury. Ten normal subjects were controls. On all days, concentrations of the key glucogenic amino acid, alanine, were the same in both groups, but levels of another glucogenic amino acid, glycine, were significantly less in the fracture patients. Other amino acid changes following injury were maximal at 7 days, with significant elevations of phenylalanine, methionine, tyrosine, ornithine, lysine, arginine, valine, isoleucine, and leucine. Increased levels of insulin, glucose, valine, isoleucine, and leucine on the fifth and seventh days after injury implied insulin resistance. Plasma glucagon was elevated on the third (p less than 0.05) and seventh (p less than 0.01) days after injury, but the concentrations measured are insufficient to explain the impaired carbohydrate tolerance following a fracture.

Arterial plasma amino acids in patients with severe burns

Arterial plasma amino acids in patients with severe burns

Arterial plasma amino acids in patients with severe burns

Arterial plasma amino acids in patients with severe burns

Plasma amino acids imbalance in patients with liver disease.

The venous plasma amino acid patterns have been determined in 12 normal individuals and in 71 shunted and nonshunted cirrhotics in various grades of hepatic encephalopathy. The free amino acids have been determined by an amino autoanalyzer; the total and free tryptophan have been measured by a spectrophotofluorimetric method. In 14 instances, arterial plasma amino acid patterns have been measured simultaneously. High levels of aromatic and sulfurated amino acids and low levels of branched-chain amino acids have been constantly found in all cirrhotics. Methionine, phenylalanine, valine, leucine, tyrosine, and free tryptophan showed a statistical difference between controls and all other groups. These altered patterns did not correlate either with the grade or the evolution of the coma or with the presence of the surgical anastomosis. No statistical differences were found between arterial and venous values. The only amino acid which statistically correlated with the grade and evolution of the hepatic encephalopathy was free tryptophan. The molar ratios between the amino acids sharing the same transport system across the blood-brain-barrier have been considered. A very good correlation with the grade of the mental disorder was found with the ratios free tryptophan/phenylalanine-tyrosine-methionine-valine-leucine-isoleucine and free tryptophan/branched-chain amino acids.

Responses to postruminal infusions of glucose and casein in lactating goats.

1. A study was made in goats of the response in terms of milk production, nitrogen utilization, plasma amino acids and glucose kinetics to postruminal infusions of glucose and casein. Goats in mid-lactation, housed in metabolism cages, were fed on 2 kg basal ration (containing 112 g crude protein (N × 6.25)/kg)/d alone (control) and with daily infusions into the abomasum of 45 g casein or 45 g glucose.2. Milk production increased with casein infusion (P &lt; 0.01), but not with glucose infusion, being 1.59, 1.86 and 1.62 kg/d with the control, casein and glucose infusions respectively. Milk composition was unaffected except for milk fat, which was decreased by the glucose infusion.3. The goats were in positive N balance on the basal ration. Milk N output increased with casein infusion, by an amount equivalent to 27% of the infused N.4. The concentration of dispensable amino acids in arterial plasma was decreased with casein infusion and increased with glucose infusion.5. Glucose kinetic measurements with control, casein and glucose infusions indicated that pool sizes were 247, 279 and 302 mg/kg live weight0.75, and irreversible losses were 5.5, 6.7 and 7.0 mg/kg live weight0.75 per min respectively. The differences between the results obtained from the glucose and casein infusions were not significant (P &lt; 0.05).6. The results of the experiment indicate that the increased milk production obtained when casein was infused was not due to enhanced gluconeogenesis.

Responses to postruminal infusions of graded levels of casein in lactating goats.

1. A study was made in goats of the response in terms of milk production, nitrogen utilization, plasma amino acids and amino acid uptake by the mammary gland, to postruminal infusion of casein. Goats in early lactation, housed in metabolism cages, were fed on 2-5 kg basal ration/d (containing 111 g crude protein (N X 6-25)/kg) and were given, by infusion into the abomasum, 0, 15, 30 or 45 g casein/d. 2. Milk production increased from 2-41 kg/d on the basal ration to 2-52, 2-80 and 2-94 kg/d in response to infusions of 15, 30 and 45 g casein/d respectively. Milk composition was unaffected except for milk fat, which was slightly decreased during infusions of the higher levels of casein. 3. The goats were found to be in positive N balance on the basal ration. Milk N output increased with casein infusion; the increase was equvalent to a miximum of 49% of the infused N. 4. The concentration of glucose in arterial blood plasma was decreased at the highest level of casein infusion but that of plasma urea N was unaffected by treatments. 5. Casein infusions increased the concentrations of total indispensable amino acids and the ratio, indispensable: dispensable amino acids in arterial plasma. Arterial concentrations and mammary extractions of most indispensable amino acis were increased, but only a few increases were statistically significant (Pless than 0-05); 6. Comparison of individual indispensable amino acids absorbed from the intestine with output in milk indicated that methionine was probably the first limiting amino acid. 7. The results of the experiment were compared to those of similar experiments with cows that have been reported by other workers. The possible ways in which the infused casein may have caused the responses were discussed. However, no firm conclusions regarding the mechanism involved could be drawn from the results of the present study.

Milk Production and Nitrogen Utilization in Response to Postruminal Infusion of Sodium Caseinate in Lactating Cows

Five lactating, rumen-fistulated Holstein cows were used to obtain additional information concerning the effects of postruminal infusion of sodium caseinate on milk production and amino acid utilization. A 7-day continuous abomasal infusion of approximately 450 g/day of sodium caseinate was preceded and followed by 7-day infusions of an isonitrogenous-isocaloric solution of glucose, monosodium glutamate, and urea. Total collections of milk, urine, and feces were obtained during the last 5 days of each infusion period. On the last day of each period, arterial and mammary venous blood samples were obtained for analysis of plasma free amino acids. During infusion of sodium caseinate, milk production, milk protein (N times 6.38) production, and efficiency of nitrogen utilization for milk crude protein production were increased. Arterial plasma concentrations of free histidine, isoleucine, phenylalanine, valine, and total essential amino acids were elevated above control levels during infusion of sodium caseinate, while ornithine and tryrosine were decreased. Calculation of the relative concentration of essential amino acids in arterial plasma and in milk protein indicated that methionine and lysine were least abundant in plasma relative to their requirement for milk protein synthesis. A high precentage extraction from arterial plasma by the mammary gland also suggested that methionine and lysine may have been the essential amino acids in most critical supply for milk protein synthesis. Calculation of uptake to output ratios of individual plasma amino acids by the mammary gland suggested that significant quantities of extracted arginine, isoleucine, leucine, threonine, and valine were utilized in pathways other than direct incorporation into milk protein.