Total Plasma Amino Acid Concentrations Research Articles

25. SUPPLEMENTATION OF FRESH HUMAN MILK WITH HUMAN MILK PROTEIN FOR FEEDING VERY-LOW-BIRTH-WEIGHT (VLBW) INFANTS

18 VLBW-infants (BW = 800-1600 g, AGA) were studied until discharge at a weight of 2000 g. All infants received mother's own milk. 9 received such milk supplemented with 1 g of ultrafiltrated human milk protein. At a milk intake of 180 ml/kg/d the protein intake varied between 2 and 4.5 g/kg/d. Protein fortification of human milk produced a higher weight gain (32.2 g/d vs. 26.4 g/d, p<0.005). The best protein utilization (weight gain per g of protein) was obtained at a protein intake of about 3 g/kg/d. Blood urea nitrogen (BUN) concentrations and other indices of protein metabolism correlated to protein intake. The mean BUN concentration was 7.2 mg% in the protein supplemented group. Protein supplementation resulted in an elevation of plasma total amino acid concentrations at the end of the study (2788 vs. 2316 μmoles/l). Individual plasma amino acid concentrations also varied with protein intake. A daily human milk protein intake of about 3 g/kg produced a rate of weight gain corresponding to that found in utero at the corresponding gestational age in VLBW-infants. The plasma responses of protein metabolism observed at this protein intake are similar to those found in term infants, breast-fed. We suggest that these results can be used as a model when evaluating feeding regimens with non-human proteins in VLBW-infants.

Free amino acid levels in muscle and liver of a patient with glucagonoma syndrome

This study set out to measure the amino acid concentrations in the femoral artery, femoral vein, hepatic vein, muscular and hepatic tissue, and urine of a patient with the glucagonoma syndrome. The total plasma amino acid concentration was severely reduced on admission (737 μmol/L, 26% of normal), with only a slight increase during intravenous administration of 200 g of amino acids per day. The total intracellular amino acid levels in the muscle were 86%, and those of the liver were 47% of the normal range. Only 0.62% of the amino acids administered were found in the urine. Arteriovenous amino acid concentration differences across the muscle and splanchnic tissue indicated the release of amino acids (mainly glutamine, glycine, and alanine) from the muscle and the absorption of amino acids by the splanchnic bed. This study shows that the infusion of a high amount of amino acids cannot increase the subnormal plasma AA levels of patients with the glucagonoma syndrome. the low total plasma AA levels are paralleled by decreased intracellular free amino acid levels in the muscle and liver.

Preserved fetal plasma amino acid concentrations in the presence of maternal hypoaminoacidemia.

The effects on the conceptus of persistently decreased maternal plasma amino acid concentrations were studied in pregnant rats by the infusion of glucagon (0.21 mg/day) to the mother from day 14 to 20 of gestation with a subcutaneous, osmotically driven minipump. Controls received diluent. The experimental animals either had normal caloric intake and weight gain, or diminished caloric intake with no weight gain. Both experimental groups exhibited a decrease in plasma total amino acid concentration of approximately 50%. Maternal plasma glucose and insulin concentrations were unaffected except for slight decreases in the low weight gain group. At cesarean section on day 20, fetal weight was unaffected in the normal weight gain group, while the low weight gain animals exhibited intrauterine growth retardation. Fetal plasma glucose and insulin concentrations were unaffected. Despite the marked decrease in maternal plasma total amino acid concentration, fetal plasma total amino acid concentration was unaffected. Individual plasma amino acid concentrations in the normal weight gain mothers and fetuses revealed a spectrum of changes. Some maternal amino acids were decreased by more than 60% (alpha-aminobutyric acid, asparagine, threonine, glutamine, alanine) while others were unaffected (tyrosine, tryptophan, phenylalanine, histidine). In general, amino acids that were decreased in the mother exhibited no change or a lesser decrease in fetal plasma concentration, while those that were unaffected in the mothers showed increased fetal concentrations. Fetuses from the low weight gain mothers had plasma amino acid profiles that were similar to those of the normal weight gain mothers.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of burns on amino acid levels in rat plasma, liver and muscle

In this study the influence of a severe catabolic situation (scalding and nitrogen deprivation) on amino acid (AA) metabolism was investigated in an experimental rat model. Scalding of 25 per cent of the total body surface area (TBSA) and hypocaloric alimentation (5–6 kcal per 100g rat per day, no nitrogen) resulted in mean daily nitrogen losses of −0·27±0·3 g. Compared to anabolic growing rats this nitrogen catabolism significantly reduced the total free AA content of muscle (−47 per cent, P<0·001) and liver (-39 per cent, P<0·001). The total plasma AA concentrations were slightly increased in catabolic rats (+10 per cent). In catabolic rats muscle glycine concentrations dropped significantly (−79 per cent, P<0·001), while glutamine concentrations decreased by 22 per cent, which was not significant. Branched chain AA and phenylalanine were significantly elevated both in muscle and in plasma. Scalding and nitrogen depletion in rats leads to characteristic changes in plasma, muscle and liver AA concentrations, which are comparable to the results obtained in catabolic patients. However, the low muscle glycine concentrations in burned rats differ from the clinical observations where glutamine rather than glycine concentrations in muscle tissue are reduced. The rat model seems to be well suited for studying the influence of various therapeutic approaches such as different forms of parenteral nutrition or hormonal substitution on nitrogen catabolism.

Urea, altered renal function, and vasopressin in Reye-Johnson syndrome

Factors which affect urea synthesis and handling are examined in RJS. BUN and blood ammonia are increased in untreated patients but no correlation between these two metabolites was found. In fatal outcomes a two-fold rise in the peak BUN was frequently seen. The total plasma amino acid concentration in RJS is nearly three and one-half times that of control subjects reflecting the increased amino acid load presented to the liver for processing. The total plasma amino acid concentration in untreated patients is even higher than that observed in a patient with liver failure. A significant reduction in arginine and an increase in ornithine levels are found in many patients. Ornithine is not a significant component of muscle actinmyosin protein whereas arginine is present nearly to the same extent as lysine. These findings suggest that the hydrolysis of arginine from the breakdown of protein by arginase (reportedly normal or increased in activity in RJS) could contribute to urea formation. Glomerular filtration rates as determined by creatinine clearances are both low and high in untreated patients. The urinary excretion of urea based on creatinine is nearly twice that of sick controls in untreated patients. Na and K excretion at comparable urine osmolarities are significantly diminished in untreated RJS patients. A peculiar pattern of an abrupt drop in urea excretion despite the presence of increased urea in the blood as well as the observation of a similarly acute drop in urea excretion in a child with varicella are presented and discussed in the light of observations of increased vasopressin levels in RJS patients above stage I.

Effect of zinc deficiency on appetite and plasma amino acid concentrations in the rat.

1. Levels of zinc in liver and plasma of the Zn-depleted rats fluctuated with the feeding cycle and were significantly higher at the bottom than at the top of the cycle. As Zn deficiency became more severe fluctuations in plasma Zn diminished. Concentrations of Zn in liver, in contrast to levels in plasma and femur, were not markedly lowered by day 15. 2. In contrast to ad lib-fed (AL) and overnight-fasted (OF) controls, some pair-fed (PF) controls had elevated levels of Zn in liver and plasma. 3. Intakes of water and food were significantly correlated in Zn-deficient rats. Packed cell volumes were significantly higher for Zn-depleted than for AL and PF rats. 4. Food intakes and plasma glucose concentrations were related in AL, OF and PF control rats but not in Zn-deficient rats. 5. At day 15 of Zn deficiency the order of total plasma amino acid concentrations in the groups of rats was AL greater than Zn-deficient greater than OF greater than PF. Many of the differences between the AL and OF groups for individual plasma amino acids also appeared in the Zn-deficient group at the top and bottom of the feeding cycle. Differences in individual amino acid concentrations at the top and bottom of the feeding cycle tended to be opposite in the PF and the Zn-deficient group. Levels of tyrosine and tryptophan in plasma were correlated (P less than 0.05) with the cyclic feeding pattern of the Zn-deficient group; however, the ratios tryptophan or tyrosine: sum of other large neutral amino acids did not correlate significantly with the eating habits of Zn-deficient rats.

Changes in plasma amino acid distribution and urine amino acids excretion during prolonged heavy exercise.

Venous plasma and urine amino acids and urea were measured in ten well-trained men, aged 23--45 years, in connection with a 70 km cross-country ski race, lasting 4.39--6.04 h, leading to slight dehydration. The estimated urea production rate during the race was of the order 7.6 mumol/min, kg b.wt, i.e. twice the rate for such men on ordinary protein intake, during ordinary activity, thus suggesting increased protein catabolism. The race led to a fall of the total plasma amino acid concentration to about 60% of the pre-race level. In particular, the branched chain amino acids (valine, iso-leucine, leucine) and alanine were markedly reduced, whereas the S-containing amino acids (taurine, cystine, methionine) and the aromatic (phenylalanine, tyrosine, trytophan, histidine) and glutamine/glutamate were increased, unchanged or only moderately reduced. It is concluded that prolonged heavy exercise is accompanied by increased protein catabolism and changes in the plasma amino acid concentrations similar to those observed during prolonged starvation, but differing from those seen at heavy exercise of less than 2 h duration or prolonged exercise of moderate intensity.

AMINO ACID METABOLISM IN DYSMATURE NEWBORN RATS: POSSIBLE EXPLANATION FOR THE ANTIHYPOGLYCEMIC EFFECT OF PRENATAL GLUCOCORTICOIDS

Using a model of intrauterine growth retardation (IUGR), we have previously shown that 91% of dysmature rat pups develop hypoglycemia 2-4 hrs after birth and that prenatal glucocorticoid treatment significantly reduces this tendency. The present study was designed to examine the possible interrelationship between the protective effect of corticoids and the metabolism of gluconeogenic (GNG) substrate. Accordingly, plasma aminograms were determined at birth and at 2-4 hrs of age in untreated (I) and treated (II) IUGR pups. Values below are in μmoles/ml. ± S.E. Compared to control newborns, both groups of IUGR pups showed higher total plasma amino acid (aa) concentrations at birth. As shown, the group given glucocorticoid had higher concentrations than untreated pups of major GNG aa, alanine or glutamine & glutamic acid. This difference was evident both at birth (ala, p<.001; gln + glu, p<.001) and at 2-4 hrs of age (ala, p<.02; gln + glu, p<.06). Thus, the reduced tendency to develop hypoglycemia after treatment is associated with greater availability of GNG aa. Furthermore, the decrease in alanine concentration after birth is greater in group II, suggesting increased utilization of this amino acid. We therefore postulate that the hormone may act to both increase the supply of GNG substrate and stimulate enzymes essential for gluconeogenesis from alanine.

Effects of starvation, surgery and infusion of adrenocorticotrophin on plasma amino acid concentrations in the pregnant ewe

Total plasma amino acid concentrations (TAA) in 12 Scottish Blackface ewes between 80 and 140 days of pregnancy were unaltered by two days of starvation, but concentrations of essential amino acids (EAA) increased and non-essential amino acid (NAA) levels decreased. These trends were more pronounced later in pregnancy. Ewes fasted before surgery to implant fetal catheters showed marked reductions in mean TAA levels (--26 per cent, n-5) on the day after operation (day+ 1). Half of this decrease was accounted for by glycine. Mean concentrations of NAA increased after day +1 but by day +6 were still 15 per cent below baseline values. In contrast mean plasma concentrations of EAA were 31 per cent above prestarvation levels on day +6 and maximal on day +4(+39 per cent). Following a two-day fast, sheep given half rations and simultaneously infused with adrenocorticotrophin showed changes in plasma-free amino acid composition like those observed during the two days after operation. Disturbances to plasma amino acid concetrations persisted for up to 12 days after operation and are attributed to the preoperative starvation and the combined effects of irregular feeding patterns and elevated plasma corticosteroid levels during and after operation.

Conditions Affecting Plasma Amino Acid Patterns in Chickens Fed Practical and Purified Diets

Experiments were conducted to investigate plasma free amino acid concentrations in the chick. After one hour of fasting, total plasma amino acid concentration decreased to approximately half of the full-fed value. Within three to six hours, most amino acids had returned toward the full-fed level but did not exceed it throughout a 48 hour period of starvation. However, after 48 hours fasting lysine, threonine, and isoleucine accumulated three-fold, two-fold and two-fold of the full-fed level, respectively. Serine and glutamic acid exceeded the full-fed level at three hours and then declined. Alanine reached its highest level after six hours of fasting and then declined.In full-fed chicks diurnal variations of plasma free amino acid concentrations were observed. The lowest and highest concentrations were observed at 11 a.m. and 8 to 11 p.m., respectively under a 24-hr lighting.Reference plasma amino acid patterns are reported for chicks fed a practical diet ad libitum. In day-old chicks, concentrations of total amino acids, methionine plus one half cystine, lysine, and arginine were high. Alanine and glutamic acid concentrations were low. Most amino acid concentrations declined gradually during the first four weeks of life, but methionine plus one half cystine, phenylalanine, threonine and serine concentrations decreased sharply between two and four weeks. Lysine concentration continued to decrease in chicks fed the starter diet. At 20 weeks, plasma amino acid concentrations had decreased considerably except for methionine plus one half cystine and basic amino acids. The plasma amino acid pattern for chicks fed an isolated soybean protein diet was similar to that of chicks fed the practical diet.

Correlation between the Plasma Tryptophan to Neutral Amino Acid Ratio and Protein Intake in the Self-selecting Weanling Rat

The relationship between changes in blood plasma amino acids and the quantity of protein and energy self-selected by the weanling rat, simultaneously offered two diets varying only in protein concentration, was examined. The changes in the quantity of protein and energy consumed by the rats, which were brought about by the addition of the essential limiting amino acids and groups of essential amino acids to gluten, casein, and zein, were not linearly related to alterations in the total plasma amino acid concentrations or to the accumulation of the added amino acids in the blood plasma. However a consistent relationship between food intake and plasma acids was identified when the plasma tryptophan to neutral amino acid ratio was correlated with the protein intake selected. It is postulated that the ratio of tryptophan to neutral amino acids in the plasma is involved in, or reflects, a mechanism regulating protein intake.

Quantitative changes in plasma amino acids induced by oral contraceptives.

1. Plasma amino acids have been determined in healthy untreated women and in those receiving synthetic steroids to suppress ovulation. Both groups were studied early in the cycle when endogenous sex hormone production is low, and again later in the same cycle, when endogenous or exogenous hormones are at high concentrations respectively. 2. In normal women there is a significant decrease in plasma concentrations of serine, glutamate and ornithine, and of total amino acids in the second half of the cycle. 3. At this time those taking oral contraceptives have significant decreases in plasma concentrations of proline, glycine, alanine, valine, leucine and tyrosine, and of total plasma amino acids. In addition plasma glutamate, glycine, isoleucine and tyrosine concentrations are significantly lower than in normal women. 4. In the interval between completing one course of contraceptive pills and commencing the next, total plasma amino acid concentration reverts to normal, but a significant decrease in plasma glycine concentration persists. 5. It is suggested that these changes are due to the influence of endogenous and exogenous sex hormones respectively.

The influence of pre-eclampsia and diabetes mellitus on plasma free amino acids in maternal, umbilical vein and infant blood.

SummaryPlasma amino acid and total protein concentrations in the mother at delivery, in the newborn infant and in the infant at the seventh day were compared for 12 small‐for‐dates infants born to mothers with severe pre‐eclampsia and low urinary oestriol excretion, 9 large‐for‐dates infants born to mothers with diabetes mellitus and normal oestriol excretion, and 26 appropriate‐weight‐for‐dates control infants born after normal pregnancy. The latter included vaginal deliveries at and before term and deliveries by Caesarean section at term.Severe pre‐eclampsia was associated with a reduced mean maternal plasma total protein concentration and a generalized increase in plasma amino acid concentrations. Plasma total protein values in the small‐for‐dates infants at birth and at the seventh day were not significantly different from values in control infants of similar gestation period, but amino acid values at birth were usually higher than those in control infants.In diabetic mothers and their infants there were increased concentrations of aspartic acid and α‐amino‐n‐butyric acid. The concentrations of the remaining amino acids and the total plasma protein concentrations did not differ from the normal control values either in mother or infant (birth and seventh day). Ten of the twenty amino acids examined in diabetic mothers and their infants showed significant positive correlations between maternal and umbilical venous values. This degree of correlation was not found in normal or pre‐eclamptic pregnancy. Due to failure of the infant to reflect fully the higher maternal levels in toxaemia, the umbilical venous/maternal venous plasma amino acid ratios for total mean plasma amino acid concentrations and particularly for the branched‐chain amino acids valine, leucine and isoleucine were reduced.The umbilical venous plasma/maternal venous plasma ratios for normal, toxaemic and diabetic pregnancy were 1.6: 1, 1.4: 1 and 1.6: 1 respectively.In small‐for‐dates infants there was a negative correlation between amino acid concentration at birth and both birthweight and umbilical venous plasma protein concentration, suggesting a possible endogenous mobilization of amino acids in such infants.

Corticoid release and gluconeogenesis following triglyceride ingestion in the rat.

AbstractFollowing a 5.0 ml triglyceride (cottonseed oil) gavage, there was a 60% elevation in the blood glucose concentration by the seventh hour in naturally occurring hypertriglyceridemic rats of the Long Evans strain. Glycogenolysis from liver or gastrocnemius muscle glycogen did not seem to be the source of this glucose. A significant elevation in the plasma total amino acid concentration concomitant with a peak in the blood urea nitrogen concentration by the fifth hour after gavage implicated gluconeogenesis. A prolonged plasma total corticoid elevation from hours 1 1/2 through 3 post‐ingestion, which did not occur in non‐fed or mineral oil‐fed cohorts, supported gluconeogenesis. The serum total protein concentration rose significantly and progressively to a peak by the eighth hour due to an elevation in the albumin concentration. These elevations in serum proteins appeared to support glucocorticoid mediated gluconeogenesis. Adrenalectomy appeared to negate triglyceride‐induced elevation in serum free amino acids, urea nitrogen, total protein and albumin.

Plasma and urinary amino acids in primary gout, with special reference to glutamine.

Measurement of the plasma free amino acids by column chromatography (AutoAnalyzer) in 32 patients with primary gout showed statistically significant increases or decreases in several components when compared with the spectrum in 18 control subjects, but the absolute amounts involved were small and the mean total plasma amino acid concentrations in both groups were the same. In the urine all major amino acid components, notably glutamine, serine, threonine, and leucine, were lower in our gouty than in our nongouty subjects, as were also the corresponding renal clearance ratios. These deficits could be reproduced by restricting dietary protein, so appear to be due largely to the some-what reduced mean dietary protein intake of our gouty subjects. However, the low renal clearance of glutamine, the most striking and consistent of the deficits in urinary amino acids noted, could not be accounted for by dietary or other relevant factors, and is interpreted as indicating increased tubular reabsorption of glutamine in primary gout. This interpretation was supported by the results of glutamine loading. The possible compensatory relationship of the abnormality in renal handling of glutamine to the deficiency in renal production of ammonia previously reported is discussed.

Effect of Prior High Protein Intake on Food Intake, Serine Dehydratase Activity and Plasma Amino Acids of Rats Fed Amino Acid-imbalanced Diets

Relationships among food intake, growth, liver serine-threonine dehydratase activity (S-TDH) and plasma amino acid concentrations were studied in rats adapted to low or high protein diets at intervals after feeding them imbalanced diets containing 5% casein and 6, 12 or 18% of an amino acid mixture devoid of histidine (AA—His). When rats adapted to the low protein diet were fed the 6% AA—His-imbalanced diet, S-TDH was low; total plasma amino acid concentrations increased; plasma histidine, food intake and growth decreased. As time progressed S-TDH increased slowly; plasma serine plus threonine concentration fell; food intake and growth began to rise. When rats adapted to the high protein diet were fed the 6% AA—His-imbalanced diet, S-TDH decreased rapidly, but food intake remained constant until S-TDH had decreased considerably and plasma serine plus threonine had risen. When rats adapted to the high protein diet were fed the more severely imbalanced diets their diminishing ability to degrade amino acids was apparently exceeded; plasma amino acids rose; food intake and growth decreased. Both alterations in food intake and amino acid-degrading capacity appear to contribute to the ability of the rat to adjust to dietary imbalances of amino acids.

Liver Function in the Chick Following X-Irradiation

Abnormal levels of some plasma constituents influenced by the activity of the liver were studied in 3-day chicks after single dose x-irradiation of 1000 r, given at 43 r/min. An approximately twofold increase in total plasma amino acid concentration was observed at 1 hour following x-irradiation and an approximately threefold increase at 3 hours following x-irradiation. Although the average increase over control values at 5 hours was the same as at 3 hours, some individual values increased to about four times the control level. Concurrently, total plasma protein decreased. There is a lack of correlation between the condition of the irradiated animal and the amino acid level or number of amino acids; increased levels occurred at 1 hour following x-irradiation in animals which appeared normal at autopsy. A similar alteration in amino acid levels has been reported in man immediately following x-irradiation; this seems to be an extremely sensitive radiation response. Mean plasma glucose levels determined in newly hatched chicks at 1, 3 and 5 hours after x-irradiation showed no significant changes from control levels. Individual animals, however, showed a hyperglycemia of 50–100 mg % over control values at 3 and 5 hours following x-irradiation. Such hyperglycemia was usually found in sick birds and was commonly associated with liver hemorrhages.