Participation of blood cells in the changes of blood amino acid concentrations during maximal exercise

We determined the participation of the cellular compartment in the changes of plasma amino acid concentrations during maximal exercise test on a cycle ergometer. Following an overnight fast, male athletes were submitted to a maximal exercise test until fatigue (for 25 min approximately) to determine maximal oxygen uptake. The amino acid concentrations in total blood, plasma, and blood cells were determined before and after the maximal exercise test. Most essential amino acids were decreased significantly in the total blood concentration as a result of the maximal exercise test. However, the concentrations of most nonessential amino acids tended to be significantly increased. Amino acid concentration was increased most in plasma. Concentrations of blood cell alanine and proline were significantly increased by 26% and 15%, respectively, after the maximal exercise test. No significant differences in blood cell concentrations of other amino acids induced by the exercise test were found, although the amount of tryptophan in blood cells was increased after exhaustive exercise.     

Effects of hypoxia on plasma amino acids of fetal sheep

Summary. Secondary amino acid disturbances from circulatory responses during hypoxia may cause problems in interpreting plasma amino acid profiles of sick babies investigated for possible inherited defects. Systematic studies to characterise them are difficult in man. We investigated the effects of hypoxia on plasma amino acids by studying 9 late gestation fetal sheep in utero during 11 one hour episodes of moderately severe isocapnic hypoxia. In 6 experiments, maternal plasma amino acids were also monitored. Fourteen fetal plasma amino acids increased significantly, with the largest proportionate changes in alanine, valine, leucine, isoleucine, phenylalanine, tyrosine, ornithine and lysine. Maternal amino acids did not increase. Probable explanations were reflex peripheral vasoconstriction in skeletal muscle beds and decreased hepatic blood flow. The findings extend our knowledge of the fetal response to hypoxic stress, demonstrate the importance of skeletal muscle in branched-chain amino acid metabolism, and should help with interpretation of postnatal plasma amino acid disturbances. Received January 29, 1999, Accepted February 22, 1999     

The effect of a single intense effort on the activity of aminotransferases and concentration of free amino acids in the plasma of rats.

Untrained rats were subjected to a single intense physical effort. In the plasma the activity of alanine aminotransferase, aspartate aminotransferase, and the concentrations of amino acids: glycine, cystine, alanine and leucine with isoleucine were measured. The results were compared with the data obtained in a control group. Despite lack of statistically significant differences in the activity of aminotransferases and concentration of amino acids between these groups a correlation was found between the activity of AIAT and alanine concentration in the animals after exercise. The concentration of alpha-amino nitrogen was decreased statistically significantly in the group of animals subjected to intensive exercise.     

The effects of high intensity exercise on muscle and plasma levels of alpha-ketoisocaproic acid

Alpha-ketoisocaproic acid (KIC) is the product of the transamination of the indispensable amino acid leucine, which is the first step in the complete degradation of leucine. To determine the effects of intense exercise on muscle and blood levels of KIC, 7 male volunteers performed cycle exercise to exhaustion. After pedaling at an intensity of 90 W for 3 min, the load was increased by 60 W every 3 min until volitional fatigue. Muscle biopsies were obtained prior to and immediately after exercise and rapidly frozen for later determination of KIC. During exercise, blood lactate levels increased as expected, while plasma KIC levels did not change. Following exercise, plasma KIC levels rose significantly with peak values occurring 15 min after exercise and did not return to pre-exercise values until 60 min after exercise. In contrast, muscle KIC levels increased during exercise from a pre-exercise mean of 49.4 +/- 4.1 mumol X kg-1 wet wt to 78.1 +/- 6.5 mumol X kg-1 after exercise, an average increase of 48% (P less than 0.05). These data indicate that during intense exercise, leucine transamination in muscle may continue at a faster rate than the decarboxylation of KIC. In addition, plasma levels of KIC did not reflect the intracellular accumulation of KIC during exercise, suggesting a delay in the diffusion of KIC from muscle.     

Changes of free amino acids in plasma of healthy subjects induced by physical exercise.

In eight healthy men a 20-min load of 1.5 W/kg body weight on a bicycle ergometer led to a significant increase of alanine and decline of leucine. Exhausting exercise caused in the same subjects a highly significant increase of alanine and decline of isoleucine, threonine, ornithine, leucine, serine, glycine, and asparasine and glutamine. The methionine and citrulline level declines also significantly. The total amino acids practically did not change. Physical exercise led furthermore to a marked increase of serum ammonia and uric acid. Urea nitrogen changed only little and on average had rather a declining tendency. The rise of alanine suggests the existence of a glucose-alanine cycle, the drop of ornithine and citrulline is most probably associated with the inhibition of ureogenesis in the liver. The reduction of leucine and isoleucine is probably the result of the entry of these amino acids into muscle and their deamination.     

Ornithine transport and exchange in Streptococcus lactis.

Resting cells of Streptococcus lactis 133 appeared to accumulate [14C]ornithine to a high concentration in the absence of an exogenous energy source. However, analysis of intracellular amino acid pool constituents and results of transport experiments revealed that the accumulation of ornithine represented a homoexchange between extracellular [14C]ornithine and unlabeled ornithine in the cell. The energy-independent exchange of ornithine was not inhibited by proton-conducting uncouplers or by metabolic inhibitors. Intracellular [14C]ornithine was retained by resting cells after suspension in a buffered medium. However, addition of unlabeled ornithine to the suspension elicited rapid exit of labeled amino acid. The initial rate of exit of [14C]ornithine was dependent on the concentration of unlabeled ornithine in the medium, but this accelerative exchange diffusion process caused no net loss of amino acid. By contrast, the presence of a fermentable energy source caused a rapid expulsion of and net decrease in the concentration of intracellular ornithine. Kinetic analyses of amino acid transport demonstrated competitive inhibition between lysine and ornithine, and data obtained by two-dimensional thin-layer chromatography established the heteroexchange of these basic amino acids. The effects of amino acids and of ornithine analogs on both entry and exit of [14C]ornithine have been examined. The data suggest that a common carrier mediates the entry and exchange of lysine, arginine, and ornithine in cells of S. lactis.     

Changes in amino acid concentration in plasma and type I and type II fibres during resistance exercise and recovery in human subjects

Eight male subjects performed leg press exercise, 4 × 10 repetitions at 80% of their maximum. Venous blood samples were taken before, during exercise and repeatedly during 2 h of recovery. From four subjects, biopsies were taken from the vastus lateralis muscle prior to, immediately after and following one and 2 h of recovery. Samples were freeze-dried, individual muscle fibres were dissected out and identified as type I or type II. Resistance exercise led to pronounced reductions in the glutamate concentration in both type I (32%) and type II fibres (70%). Alanine concentration was elevated 60–75% in both fibre types and 29% in plasma. Glutamine concentration remained unchanged after exercise; although 2 h later the concentrations in both types of fibres were reduced 30–35%. Two hours after exercise, the plasma levels of glutamate and six of the essential amino acids, including the branched-chain amino acids were reduced 5–30%. The data suggest that glutamate acts as an important intermediate in muscle energy metabolism during resistance exercise, especially in type II fibres.     

Glutamate ingestion: the plasma and muscle free amino acid pools of resting humans

Monosodium glutamate (MSG) ingestion is known to increase plasma glutamate concentration, and MSG infusion stimulates insulin secretion. We investigated the impact of MSG ingestion on both the plasma and intramuscular amino acid pools. Nine postprandial adults ingested MSG (150 mg/kg) and rested for 105 min. Venous blood was sampled preingestion and then every 15 min; vastus lateralis muscle biopsies were taken preingestion and at 45, 75, and 105 min postingestion. Venous plasma glutamate and aspartate concentrations increased (P 相似文献   

Effect of local x-ray irradiation of the abdominal area on the amino acid content of the blood plasma and their urinary excretion in dogs and rats

A study was made of the content of amino acids in blood plasma of dogs and rats and daily excretion thereof from rat body in urine after local X-irradiation of abdomen with a dose of 13.5 Gy. As the gastrointestinal syndrome developed the content and excretion of taurine increased, glucogenic amino acid content of plasma decreased, and the ratio of phenylalanine to tyrosine and branched-chain amino acids to aromatic amino acids changed. The ratio of arginine to ornithine and urea to ammonia sharply dropped in animals, which died later on, indicating that the urea-producing function of liver was impaired and hyperammonemia developed.     

An amino acid mixture is essential to optimize insulin-stimulated glucose uptake and GLUT4 translocation in perfused rodent hindlimb muscle

The purpose of this study was to investigate whether an amino acid mixture increases glucose uptake across perfused rodent hindlimb muscle in the presence and absence of a submaximal insulin concentration, and if the increase in glucose uptake is related to an increase in GLUT4 plasma membrane density. Sprague-Dawley rats were separated into one of four treatment groups: basal, amino acid mixture, submaximal insulin, or amino acid mixture with submaximal insulin. Glucose uptake was greater for both insulin-stimulated treatments compared with the non-insulin-stimulated treatment groups but amino acids only increased glucose uptake in the presence of insulin. Phosphatidylinositol 3-kinase (PI 3-kinase) activity was greater for both insulin-stimulated treatments with amino acids having no additional impact. Akt substrate of 160 kDa (AS160) phosphorylation, however, was increased by the amino acids in the presence of insulin, but not in the absence of insulin. AMPK was unaffected by insulin or amino acids. Plasma membrane GLUT4 protein concentration was greater in the rats treated with insulin compared with no insulin in the perfusate. In the presence of insulin, amino acids increased GLUT4 density in the plasma membrane but had no effect in the absence of insulin. AS160 phosphorylation and plasma membrane GLUT4 density accounted for 76% of the variability in muscle glucose uptake. Collectively, these findings suggest that the beneficial effects of an amino acid mixture on skeletal muscle glucose uptake, in the presence of a submaximal insulin concentration, are due to an increase in AS160 phosphorylation and plasma membrane-associated GLUT4, but independent of PI 3-kinase and AMPK activation.     

Blood cell NO synthesis in response to exercise.

Nitric oxide (NO) is important for the maintenance of cardiovascular homeostasis and is also involved in immunity and inflammation. The aim of our work was to determine the effects of intense exercise on plasma and blood cell NO handling. Nine voluntary male professional cyclists participated in the study. Blood samples were taken in basal conditions and 3h after finishing a mountain cycling stage. Exercise-induced neutrophilia, lymphopenia, and hemolysis. Plasma and erythrocytes maintained basal nitrite levels, whereas neutrophils and lymphocytes decreased nitrite concentration after intense exercise. Basal iNOS levels and SOD activity were similar in neutrophils and lymphocytes. iNOS levels and SOD activity dropped in neutrophils and rose in lymphocytes after exercise. Arginase activity rose only in lymphocytes. Neutrophil nitrite was correlated with SOD activity and iNOS levels, but not in lymphocytes. iNOS levels were correlated with SOD in both neutrophils and lymphocytes. Intense exercise maintained plasma basal arginine and ornithine concentration, and decreased citrulline concentration. Intense exercise induced important changes in NO handling in neutrophils and lymphocytes, yet the basal picture was maintained in erythrocytes.     

Effect of dietary amino acid on the amino acid pool of Aedes aegypti

Ion-exchange chromatography analysis of whole body extracts of Aedes aegypti mosquitoes which had received amino acids in their diet revealed that generally there were changes in the titre of two or more amino acids. Cysteine produced the greatest number of changes and was toxic to the insect. Of the ten amino acids provided, none resulted in the significant change in the concentration of tyrosine following a blood meal as was observed in previous studies. Evidence is presented for the conversion of arginine to ornithine and for the synthesis of arginine from glutamic acid. The data presented tend to support the hypothesis of lysine synthesis from α-ketoglutarate and for the use of proline as an energy reserve in the insect.     

Inverse relationship between protein intake and plasma free amino acids in healthy men at physical exercise

The effect of a "normal" (n = 8) and "high" (n = 6) protein intake (1 and 2.5 g x kg(-1) x day(-1), respectively) and of exercise on plasma amino acid (AA) concentrations, insulin, and glucagon concentrations was followed throughout a continuous 24-h period in adult male subjects at energy balance after six days on a standardized diet and exercise program. Subjects were fasting from 2100 on day 6 to 1200 on day 7 and then fed 10 identical meals hourly until 2100. Physical exercise was performed (46% maximal oxygen uptake) between 0830 and 1000 (fasting) and in a fed state (1600-1730) on each day. The normal-protein group showed fasting plasma AA concentrations that were higher (P < 0.05) than those for the high-protein group, except for leucine, methionine, and tyrosine. Glutamine, glycine, alanine, taurine, and threonine concentrations were distinctly higher ( approximately 30% or greater) throughout the 24-h period in subjects consuming the normal- vs. the high-protein diets. Exercise appeared to increase, although not profoundly, the plasma concentrations of amino acids except for glutamate, histidine, ornithine, and tryptophan. The profound diet-related differences in plasma AA concentrations are only partially explained by differences in the renal clearance of the amino acids. We speculate on the possible metabolic basis for these findings.     

The whey proteins of the milk of red deer (Cervus elaphus L.). A homologue of bovine beta-lactoglobulin.

Increasing plasma free fatty acids decreased the degree of glycogen depletion, and increased the citrate concentration, in slow-red (soleus) and fast-red (deep portion of vastus lateralis) muscle during exercise (approx. 50% depletion of glycogen, as against 75% in control animals). There was no effect in fast-white muscle (superficial portion of vastus lateralis). Glycogen concentration in the liver decreased by 83% in controls, but only by 23% in animals with increased free fatty acids during exercise. The decreased glycogen depletion may be partly explained by the findings that (a) plasma-insulin concentration was two- to three-fold higher in animals with increased plasma free fatty acids and (b) the exercise-induced increase in plasma glucagon was lessened by increased free fatty acids. Blood glucose was higher in the animals with increased free fatty acids after the exercise. The rats with increased plasma free fatty acids utilized approx. 50% as much carbohydrate as did the controls during the exercise.     

Control of ureogenesis

Control of urea synthesis was studied in rat hepatocytes incubated with physiological mixtures of amino acids in which arginine was replaced by equimolar amounts of ornithine. The following observations were made. Intramitochondrial carbamoyl phosphate was always below 0.1 mM. Only when ornithine was absent and when, in addition, the concentration of amino acids was higher than four times their plasma concentration, intramitochondrial carbamoyl phosphate rose up to about 3 mM; under these conditions ammonia accumulated in the medium. The relationship between ornithine-cycle flux and the concentration of the cycle intermediates at varying amino acid concentration indicated that under near-physiological conditions the ornithine-cycle enzymes are far from being saturated with their subsidiaries. Moderate concentrations of norvaline had no effect on the rate of urea synthesis unless the cells were severely depleted of ornithine. Activation of carbamoyl-phosphate synthetase (ammonia) by addition of N-carbamoylglutamate only slightly stimulated urea production at all amino acid concentrations. However, in the presence of the activator the curve relating ornithine-cycle flux to the steady-state ammonia concentration was shifted to lower concentrations of ammonia. The intramitochondrial concentration of carbamoyl phosphate in rat liver in vivo was below 0.1 mM. This value is far below the concentration required for substantial inhibition of carbamoyl-phosphate synthetase. It is concluded that in vivo the function of activity changes in carbamoyl-phosphate synthetase, via the well-documented alterations in the intramitochondrial concentration of N-acetylglutamate, is to buffer the intrahepatic ammonia concentration rather than to affect urea production per se. At constant concentration of ammonia the rate of urea production is entirely controlled by the activity of carbamoyl-phosphate synthetase.     

Application of amino acid analysis by high-performance liquid chromatography with phenyl isothiocyanate derivatization to the rapid determination of free amino acids in biological samples

An amino acid analysis by reversed-phase high-performance liquid chromatography after precolumn derivatization with phenyl isothiocyanate was adapted to the determination of free amino acids in plasma or other biological fluids and in tissue homogenates. Preparation of samples included deproteinization by 3% sulphosalicylic acid, and careful removal under high vacuum of residual phenyl isothiocyanate after derivatization. A Waters Pico-Tag column (15 cm long) was used, immersed in a water-bath at 38°C. In rat or human plasma, separation of 23 individual amino acids, plus the unresolved pair tryptophan and ornithine, was obtained within 13 min. Including the time for column washing and re-equilibration, samples could be chromatographed at 23-min intervals. Variability was tested for each amino acid by calculating the coefficients of variation of retention times (less than 1% in the average) and peak areas (less than 4% for both intra-day and inter-day determinations). The linearity for each standard amino acid was remarkable over the concentration range 3–50 nmol/ml. The mean recovery of amino acid standards added to plasma prior to derivatization was 97 ± 0.8%, except for aspartate (82%) and glutamate (81%). This method is rapid (almost three samples per hour can be analysed, more than in any other reported technique), with satisfactory precision, sensitivity and reproducibility. Therefore, it is well suited for routine analysis of free amino acids in both clinical and research work.     

Effect of arginine,ornithine and citrulline supplementation upon performance and metabolism of trained rats

During intense exercise there is an augmented production of ammonia and IMP in the exercised muscle that could be related to the establishment of peripheral fatigue. In order to prevent this accumulation, the urea cycle in the liver eliminates ammonia in the form of urea and the skeletal muscle buffers the increase of ammonia via transamination reactions. In the present study we evaluated the effect of arginine, citrulline and ornithine supplementation, intermediates of the urea cycle, on the performance of sedentary and swimming-trained rats submitted to a single bout of exhaustive exercise. We also measured the glycogen content of the soleus and gastrocnemius muscles and of the liver, as well as the plasma concentrations of ammonia, urea, glutamine, glucose and lactate. The results indicate that arginine, citrulline and ornithine supplementation increased the flux of substrate through the reaction catalysed by glutamine synthetase, leading to increased glutamine production after an exhaustive bout of exercise, and of the mechanism involved in ammonia buffering.     

Hypogonadism in liver cirrhosis: implication in altered amino acid metabolism in muscle

To investigate the relationship between hypogonadism and altered amino acid metabolism in patients with liver cirrhosis, we measured the basal levels of plasma testosterone, estradiol, and free amino acids, plus urinary 3-methylhistidine excretion, in 16 control and 19 cirrhotic patients. The concentration of plasma testosterone correlated significantly with that of plasma branched-chain amino acids, and inversely with urinary 3-methylhistidine excretion. This suggests that hypogonadism causes a disturbance in amino acid metabolism at least partly related to an augmented muscle protein turnover.     

Quantitative study of free amino acids in human eccrine sweat excreted from the forearms of healthy trained and untrained men during exercise

The free amino acids in eccrine sweat collected from the forearms of 20 healthy trained and 20 healthy untrained men during controlled exercise were determined quantitatively using ion exchange column chromatography. Sweat was deproteinized by adding an equal volume of 5% sulphosalicylic acid. The amino acid concentrations showed a constant qualitative pattern in sweat and large individual differences. Essential amino acids, such as isoleucine, leucine, lysine, methionine, phenylalanine, and valine were excreted in relatively small amounts. As compared to the trained men, untrained men showed statistically significantly higher concentrations in sweat for the following amino acids: Alanine, arginine, glycine, histidine, isoleucine, leucine, lysine, ornithine, phenylalanine, serine, taurine, threonine, tyrosine, and valine. No significant differences were found for citrulline, cystine, ethanolamine, and methionine. The comparison of the amino acid excretions in sweat obtained under controlled exercise and in urine showed that the amounts of amino acids excreted in sweat under controlled exercise were comparable to the losses of amino acids in urine.     

Effect of plasma free fatty acid concentration on the content and composition of the free fatty acid fraction in rat skeletal muscles.

Skeletal muscles contain a fraction of free (unesterified) fatty acids. This fraction is very small, but important since it contributes to the creation of the plasma-myocyte free fatty acid concentration gradient. Maintenance of this gradient is necessary for blood-borne fatty acids to be transported into the cell. There are no data on the regulation of the content and composition of the free fatty acid fraction in the cell. The aim of the present study was to examine the effect of an elevation and a reduction in the plasma-borne free fatty acid concentration on the content and composition of the free fatty acid fraction in different skeletal muscle types. The experiments were carried out on male Wistar rats with 280 - 310 g body weight. They were divided into four groups - 1, control; 2, exercised 3 h on a treadmill moving with a speed of 1,200 m/h and set at + 10 degrees incline; 3, treated with heparin; and 4, treated with nicotinic acid. Samples of the soleus as well as the red and white sections of the gastrocnemius muscles were taken. These muscles are composed mostly of slow-twitch oxidative, fast-twitch oxidative-glycolytic and fast-twitch glycolytic fibres, respectively. Lipids were extracted from the muscle samples and from the blood; the free fatty acid fraction was isolated by means of thin-layer chromatography. The individual free fatty acids were identified and quantified using gas-liquid chromatography. The plasma concentration of free fatty acids was as follows: control group, 236.1 +/- 32.9; after exercise, 407.4 +/- 117.5; after heparin, 400.8 +/- 36.8; and after nicotinic acid, 102.5 +/- 26.1 micromol/l (p < 0.01 vs. control values in each case). The total content of the free fatty acid fraction in the control group was as follows: white gastrocnemius, 27.6 +/- 7.3; red gastrocnemius, 52.2 +/- 13.9; soleus, 72.3 +/- 10.2 nmol/g. Elevation in plasma free acid concentration during exercise increased the total content of free fatty acids in the white gastrocnemius (38.7 +/- 13.9) and in the soleus (103.4 +/- 15.9 nmol/g; rest-exercise: p < 0.05 and p < 0.01, respectively), but had no effect in the red gastrocnemius. Neither elevation in the plasma free fatty acid concentration with heparin nor reduction with nicotinic acid affected the total content of the free fatty acid fraction in the muscles examined. The ratio of plasma concentration of individual acid to muscle concentration for the same acid varied greatly, depending on acid, muscle type and experimental group. The ratio was positive (above unity) for each acid almost in all cases with the exception of certain acids in the nicotinic acid-treated group where it was below unity. We conclude that the skeletal myocytes maintain a stable level of free fatty acid fraction in the wide range of plasma free fatty acid concentrations.