Rate Of Glutamine Utilization Research Articles

The mTORC1/S6K1 Pathway Regulates Glutamine Metabolism through the eIF4B-Dependent Control of c-Myc Translation

Growth-promoting signaling molecules, including the mammalian target of rapamycin complex 1 (mTORC1), drive the metabolic reprogramming of cancer cells required to support their biosynthetic needs for rapid growth and proliferation. Glutamine is catabolyzed to α-ketoglutarate (αKG), a tricarboxylic acid (TCA) cycle intermediate, through two deamination reactions, the first requiring glutaminase (GLS) to generate glutamate and the second occurring via glutamate dehydrogenase (GDH) or transaminases. Activation of the mTORC1 pathway has been shown previously to promote the anaplerotic entry of glutamine to the TCA cycle via GDH. Moreover, mTORC1 activation also stimulates the uptake of glutamine, but the mechanism is unknown. It is generally thought that rates of glutamine utilization are limited by mitochondrial uptake via GLS, suggesting that, in addition to GDH, mTORC1 could regulate GLS. Here we demonstrate that mTORC1 positively regulates GLS and glutamine flux through this enzyme. We show that mTORC1 controls GLS levels through the S6K1-dependent regulation of c-Myc (Myc). Molecularly, S6K1 enhances Myc translation efficiency by modulating the phosphorylation of eukaryotic initiation factor eIF4B, which is critical to unwind its structured 5' untranslated region (5'UTR). Finally, our data show that the pharmacological inhibition of GLS is a promising target in pancreatic cancers expressing low levels of PTEN.

Glutamine as an energy substrate in cultured neurons during glucose deprivation

During glucose deprivation an increase in aspartate formation from glutamine has been observed in different brain preparations, including synaptosomes and cultured astrocytes. To what extent this reaction, which provides a substantial amount of energy, occurs in different types of neurons is unknown. The present study shows that (14)CO(2) formation from [U-(14)C]glutamine in cerebellar granule neurons, a glutamatergic preparation, increased by 60% during glucose deprivation, indicating enhanced aspartate formation or increased complete oxidative degradation of glutamine. In primary cultures of cerebrocortical interneurons, a GABAergic preparation, the rate of (14)CO(2) production from [U-(14) C] glutamine was four times lower and not stimulated by glucose deprivation. During incubation with glutamine (0.8 mM) as the only metabolic substrate, cerebellar granule cells maintained an oxygen consumption rate of 12 nmol/min/mg protein, corresponding to an aspartate formation of 8 nmol/min/mg protein (three oxidations occur between glutamine and aspartate) or to a total oxidative degradation of 3 nmol/min/mg protein. During glucose deprivation, the rate of aspartate formation increased, and during a 20-min incubation in phosphate-buffered saline it amounted to 3.3 nmol/min/mg protein at 0.2 mM glutamine, which might have been more if measured at 0.8 mM glutamine. These values are consistent with the rate of glutamine utilization calculated based on oxygen consumption and leaves open the possibility that some glutamine is completely degraded oxidatively, as has been shown by other authors based on pyruvate recycling and labeling of lactate from aspartate in cerebellar granule neurons.

Changes in salinity and ionic compositions can act as environmental signals to induce a reduction in ammonia production in the African lungfishProtopterus dolloi

The slender African lungfish, Protopterus dolloi, does not aestivate in a subterranean mud cocoon, but is capable of aestivating inside a layer of dried mucus on land during drought. In this study, we aimed to elucidate if a slight increase in salinity in association with changes in the ionic composition could act as signals for P. dolloi to decrease endogenous ammonia production, in preparation for aestivation when the external medium dries up. Specimens of P. dolloi exposed to 3 per thousand water for 6 days exhibited consistently lower daily urea excretion rate than the freshwater control. This led to significant decreases in the cumulative total nitrogenous wastes excreted on days 3, 5 and 6. On day 6, there were decreases in urea contents in various tissues and organs. Taken together, these results suggest that there was a decrease in the rate of urea synthesis, the magnitude of which was greater than the decrease in the rate of urea excretion, and therefore resulted in decreases in internal urea contents. A decrease in the rate of urea synthesis should result in a decrease in the rate of glutamine utilization, and subsequently led to the accumulations of glutamine and/or ammonia. However, there were no changes in contents of glutamine and ammonia in various tissues and organs in the experimental animals. A logical explanation for this is that there must be a simultaneous reduction in ammonia production; if not, ammonia would accumulate due to the decrease in rate of urea synthesis. Since fish were unfed during the experiment, endogenous ammonia must be derived mainly from amino acid catabolism. Therefore, these results suggest that a suppression of amino acid catabolism occurred in specimens exposed to 3 per thousand for 6 days. The differences in effects of freshwater and 3 per thousand water on endogenous ammonia production could not be due to food deprivation because both groups of fish were fasted for the same period. Because control and experimental fish were kept in water and because there were no changes in the wet mass of the fish and blood osmolality before and after the experiment, dehydration did not occur. Furthermore, both groups of fish have comparable blood pH, pO2 and pCO2 on day 6 as they had free access to air, and therefore CO2 retention could be eliminated as the initiating factor of suppressed endogenous ammonia production. In conclusion, our results suggest that P. dolloi could respond to increases in salinity and changes in ionic composition in the external medium by suppressing ammonia production in preparation for aestivation when the water dries up.

운동의 분자생물학적 탐색

The purpose of study to phenomenological examine and the mechanism regarding the gene(DNA, RNA, Protein) and sports to studied, analyzed, and evaluated. This review considers the evidence for genetic effects in several determinants of endurance performance and resistance performance, namely : body measurements and physique, body fat pulmonary functions, cardiac and circulatory functions, muscle characteristics, substrate utilization, maximal aerobic power and other. Moreover, the response to aerobic training of indicators aerobic work metabolism and endurance performance is reviewed, with emphasis on the specificity of the response and the individual differences observed in training ability. This study indicate that improvement of `Enhancer Action` in RNA genes changed by exercise or sports. Moreover exercise was effect on Central Dogma with DNA makes RNA makes Protein. and think that occurred with exercise influence on skeletal muscle into cell have to Myosin Heavy Chain(MHC) changed was after exercise performance, which accompanied into skeletal muscle that were exercise-induces gene-modulation that is, take gene mutations. This study known that existed hormone(epinephrine)-immune system with interaction. Exercise were altered insulin binding and MAP Kinase signaling increased into immune cells. This review suggested that the high rate of glutamine utilization by cells of the immune system serves to maintain a high intra cellular concentration of the intermediates of biosynthetic pathways such that optimal rates of DNA, RNA and protein synthesis can be maintained. In the absence of glutamine, lymphocytes do not proliferate in vitro; proliferation increase greatly as the glutamine concentration increase. Glutamine is synthesized in skeletal muscle. Skeletal muscle and plasma glutamine levels are lowered by sepsis, injury, bums, surgery and endurance exercise and in the overtrained athlete. The study of result show that production of ET-1 is markedly increased tissue specifically in the heart by exercise without appreciable changes in endothelin-converting enzyme and endothelial receptor expressions, suggest that myocardial ET-1 may participate in modulation of cardiac function during exercise. Conclusionally, this study indicate that improvement of `Enhancer Action` in RNA genes changed by exercise or sports. Moreover exercise was effect on Central Dogma with DNA makes RNA makes Protein. This study is expected to contribute the area of sports science, medicine, hereafter more effort is required to establish the relation between gene alters and exercise amount.

Why Is L-Glutamine Metabolism Important to Cells of the Immune System in Health, Postinjury, Surgery or Infection?

Glutamine is normally considered to be a nonessential amino acid. However, recent studies have provided evidence that glutamine may become "conditionally essential" during inflammatory conditions such as infection and injury. It is now well documented that under appropriate conditions, glutamine is essential for cell proliferation, that it can act as a respiratory fuel and that it can enhance the function of stimulated immune cells. Studies thus far have determined the effect of extracellular glutamine concentration on lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities and neutrophil bacterial killing. Other cells of the immune system remain to be studied. The high rate of glutamine utilization and its importance to the function of lymphocytes, macrophages and neutrophils have raised the question "why glutamine?" because these cells have access to a variety of metabolic fuels both in vivo and in vitro. I have attempted to answer this question in this article. Additionally, knowledge of the rate of utilization and the pathway of metabolism of glutamine by cells of the immune system raises some intriguing questions concerning therapeutic manipulation of utilization of this amino acid such that the proliferative, phagocytic and secretory capacities of cells of the defense system may be beneficially altered. Evidence to support the hypothesis that glutamine is beneficially immunomodulatory in animal models of infection and trauma, as well as trauma in humans, is provided.

Cloning and analysis of unique human glutaminase isoforms generated by tissue-specific alternative splicing.

Three human glutaminase (hGA) isoforms were identified, two of which represent isoforms previously unidentified in any species. One isoform contains an open reading frame with high homology with the rat kidney-type glutaminase, suggesting that this isoform represents the human kidney-type glutaminase, hKGA. A second isoform, termed hGAC, contains an open reading frame that matches hKGA except for a unique COOH-terminal amino acid sequence. In addition, a third human glutaminase isoform was identified from a computer search and on further analysis was found to represent an additional unique isoform, hGAM. hKGA is expressed predominantly in brain and kidney but not in liver, hGAC is expressed principally in cardiac muscle and pancreas but not in liver or brain, and hGAM is expressed solely in cardiac and skeletal muscle. hGAC is the predominant isoform expressed by a human breast cancer cell line that exhibits a high rate of glutamine utilization and glutaminase activity. Genomic Southern analysis as well as isolation and analysis of five glutaminase genomic clones suggested that all three hGA isoforms originate from the same locus and therefore represent mRNA species that are produced by tissue-specific alternative splicing of a single pre-mRNA. Furthermore, an RT-PCR assay was developed that can be used to easily differentiate between hKGA and hGAC mRNA species.

Metabolic fate of glutamine in lymphocytes, macrophages and neutrophils.

Eric Newsholme's laboratory was the first to show glutamine utilization by lymphocytes and macrophages. Recently, we have found that neutrophils also utilize glutamine. This amino acid has been shown to play a role in lymphocyte proliferation, cytokine production by lymphocytes and macrophages and phagocytosis and superoxide production by macrophages and neutrophils. Knowledge of the metabolic fate of glutamine in these cells is important for the understanding of the role and function of this amino acid in the maintenance of the proliferative, phagocytic and secretory capacities of these cells. Glutamine and glucose are poorly oxidized by these cells and might produce important precursors for DNA, RNA, protein and lipid synthesis. The high rate of glutamine utilization and its importance in such cells have raised the question as to the source of this glutamine, which, according to current evidence, appears to be muscle.

Macrophage-mediated lysis of a β-cell line, tumour necrosis factor-α release from bacillus Calmette–Gue´rin (BCG)-activated murine macrophages and interleukin-8 release from human monocytes are dependent on extracellular glutamine concentration and glutamine metabolism

Macrophages and monocytes are cells with a large capacity for cytokine production. Cytokines produced by these cells are not preformed and released upon stimulation, but must be transcribed and translated. Although much is known concerning the regulation of the latter processes at the molecular level, the role of exogenous amino acids in the secretory process has not been actively investigated. Glutamine is utilized by macrophages at a much faster rate than any other amino acid. The role for high rates of glutamine utilization in macrophages or monocytes is not fully understood. We demonstrate here that the rates of lipopolysaccharide-stimulated tumour necrosis factor-alpha secretion from bacillus Calmette-Guérin (BCG)-activated murine peritoneal macrophages and lipopolysaccharide-stimulated interleukin-8 production from human monocytes are dependent upon extracellular glutamine concentration. We also demonstrate that potent inhibition of cytokine production can be achieved by incubating macrophages or monocytes in the presence of the glutaminase inhibitor 6-diazo-5-oxo-norleucine. On co-culture of BCG-activated macrophages and the clonal pancreatic beta-cell line BRIN-BD11, macrophage-specific beta-cell death was significantly reduced on prior exposure of macrophages to 6-diazo-5-oxo-norleucine. Thus glutamine metabolism may be essential for generation of cytotoxic products from macrophages, including tumour necrosis factor-alpha.

Protein and energy metabolism in prepubertal children with sickle cell anemia.

We hypothesized that, in children with homozygous sickle cell anemia (HbSS), the shortened life-span of erythrocytes places an increased demand on protein stores, accelerates whole body protein turnover, and consequently, energy expenditure, as well as the rate of utilization of glutamine, a major fuel for reticulocytes. Eight (11.2 +/- 0.4 y old) children with HbSS who were free of infection of vaso-occlusive disease, and seven (11.3 +/- 0.4 y old) healthy black children were therefore studied in the postabsorptive state. Each received a continuous 4-h infusion of L-[1-(13)C]leucine to determine the rate of leucine oxidation, leucine rate of appearance, and nonoxidative leucine disposal, indicators of whole body protein breakdown and synthesis, respectively. Infusion of L-[2-(15)N]glutamine was used to assess rates of glutamine utilization. Resting energy expenditure and cardiac output were measured using indirect calorimetry and echocardiography, respectively. Compared with control subjects, HbSS children had a 58 and 65% higher leucine rate of appearance and nonxidative leucine disposal, respectively (both p < 0.001), 47% higher rates of whole body glutamine utilization (p < 0.01), 19% higher resting energy expenditure (p < 0.05), and 66% higher cardiac output (p < 0.01). In conclusion, children with HbSS show evidence of hypermetabolism with regard to protein, energy, and glutamine utilization. Both increased Hb synthesis and increased cardiac workload may contribute to excess protein and energy utilization. Whatever the mechanism of hypermetabolism, the data suggest that children with HbSS may have greater protein and energy requirements than the general population.

Glutamine utilization in resting and stimulated platelets.

Exogenous glutamine was metabolized by platelets to glutamate, aspartate, and CO2; whereas no lactate was formed. The amount of aspartate and CO2 produced from glutamine was reduced by the presence of glucose. On the other hand the rate of oxidation of glucose was reduced by the presence of glutamine. The potential energetic value of glutamine was lower than that of glucose, but the amino acid appeared to be a preferential respiratory substrate. The energy provision from glutamine also plays a role in the process of platelet activation, known to require an extra supply of ATP, since thrombin increased the rate of glutamine utilization in platelets. Upon cell activation an increase in aspartate and CO2 formation was observed and the stimulatory effect on glutamine oxidation by thrombin was also maintained in the presence of glucose.

15N n.m.r. measurement of the in vivo rate of glutamine synthesis and utilization at steady state in the brain of the hyperammonaemic rat

The rate of glutamine synthesis and utilization at steady state was measured in vivo in the brains of hyperammonaemic rats by 15N n.m.r. in combination with biochemical techniques. Rats were given an intravenous 15NH4+ infusion at the rate of 4.8 +/- 0.3 mmol/h per kg body wt. for 3.5 +/- 0.2 h, followed by 14NH4+ infusion at the same rate for an additional 5.1 h (chase period). During the chase period, blood ammonia (0.61 +/- 0.015 mumol/g), brain ammonia (2.9 +/- 0.3 mumol/g), glutamate (9.4 +/- 0.8 mumol/g) and glutamine (15N + 14N; 14.4 +/- 1.3 mumol/g) were at steady state. The rate of change in the cerebral [5-15N]glutamine concentration was measured in vivo by 15N n.m.r. at 20.27 MHz. To estimate 15N enrichment of precursor ammonia for glutamine synthetase (GS) in astrocytes which are interposed between cerebral capillaries and neurons, 15N enrichments of blood and brain ammonia were measured by gas chromatography-mass spectrometry. The in vivo rate of glutamine synthesis, which is equal to the rate of glutamine utilization at steady state, was estimated, from the observed rate of change in [5-15N]glutamine concentration and 15N enrichment of brain glutamine, to be 4.8 +/- 1.1 mumol/h per g of brain if 15N enrichment of ammonia at the site of GS in astrocytes is equal to that of blood-borne ammonia, and 13.0 +/- 3.9 mumol/h per g if it is equal to that measured for the whole brain. The observed GS activity in vivo in the brain of the hyperammonaemic rat is 2-5% of the reported optimum activity in vitro measured at enzyme-saturating concentrations of all substrates. The result suggests that substrates and/or cofactors other than ammonia kinetically limit GS activity in vivo. The g.c. chromatogram and mass spectrum of ammonia-derived N-trifluoroacetyl-dibutylglutamate (TAB-glutamate) are shown in Supplementary Publication SUP 50170 (4 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire, U.K., from whom copies can be obtained on the terms indicated in Biochem. J.

Characterization of glutamine metabolism in two related murine hybridomas

Aspects of glutamine metabolism were examined in two related hybridomas, a high-producing line (PQX B1/2) and a low-producing line (PQX B2/2). The growth and metabolic characteristics of both cell lines were identical or very similar. During batch growth glutamine was completely exhausted from the medium and an examination of the fate of [ 14C]glutamine highlighted the importance of this amino acid as an energy source. The relative enzyme activities and the amount of ammonia produced during growth indicated that glutamine is oxidized preferentially via the transamination pathway. The overall rate of glutamine utilization from the growth medium was similar to the rate of [ 14C]glutamine uptake which suggests that transport may regulate glutamine metabolism.

The effect of time of addition of glutamine or nucleosides on proliferation of rat cervical lymph-node T-lymphocytes after stimulation by concanavalin A

1. Addition of concanavalin A to T-cell lymphocytes from rat cervical lymph nodes increases the activity of glutaminase within 1 h and those of carbamoyl-phosphate synthase II and aspartate transcarbamoylase within 3 h. There was a similar time course for the effects of concanavalin A on rates of glutamine utilization, which was increased within 1 h, and on pyrimidine nucleotide synthesis, which was increased by 40% at 2 h and by 100% at 3 h. 2. A delay in the addition of glutamine to the culture medium after addition of concanavalin A caused a decrease in [3H]thymidine incorporation only after 4-6 h. In the absence of glutamine, delay in addition of guanosine or inosine caused a decrease in [3H]thymidine incorporation only after 6-8 h after the addition of concanavalin A. 3. In contrast, a delay in addition of adenosine or uridine to the culture medium had an immediate effect (i.e. within 2 h) on the rate of incorporation of [3H]thymidine. It is suggested that adenosine and uridine have specific effects on proliferation via specific receptors for these nucleosides in the membrane.

Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by lungs of the rat

The maximum activities of some key enzymes of metabolism were studied in lungs of fed and 48-h-starved rats. The maximum activity of hexokinase in the lung is similar to that of other tissues of the body, but lower than that of phosphorylase and 6-phosphofructokinase. High activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were found in lung tissue, suggesting the importance of the pentose phosphate pathway in the lung. The activities of hexokinase and 6-phosphofructokinase were decreased whereas that of phosphorylase increased in response to starvation. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (≈ 4.2 nmol/min per mg protein at 37°C) was considerably greater than the flux through the cycle (0.46 nmol/min per mg protein at 37°C; calculated from oxygen consumption by incubated lung slices). The activities of both oxoglutarate dehydrogenase and citrate synthase were decreased by starvation. The activities of 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase were low in lung tissue compared to those of other tissues ( eg kidney, brain) and that of 3-hydroxybutyrate dehydrogenase was very low. The activity of carnitine palmitoyl transferase is higher in the lung, suggesting that fatty acids (and possibly acetoacetate) could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. Very low rates of utilization of 3-hydroxybutyrate were observed during incubation of lung slices, but that of oleate was 1.2 nmol/h per mg of protein. The activity of glutaminase was present in the lung at a moderate value suggesting that glutamine could be utilized by the lung. Thus the possible enzymes involved in the glutaminolytic pathway were measured in lungs. The latter suggests that an aminotransferase reaction(s) is important in the conversion of glutamate into oxoglutarate rather than glutamate dehydrogenase, and that the maximum activity of glutaminase is markedly in excess of the rate of glutamine utilization by incubated lung slices. The activity of glutaminase was decreased by starvation.

Application of metabolic-control logic to fuel utilization and its significance in tumor cells

The importance and the value of applying metabolic-control logic to the question of fuels, their rates of utilization and their significance to the process of proliferation are presented. Application of the recently developed quantitative theory of metabolic control of branched pathways provides a hypothesis to account for the high rate of both glycolysis and glutaminolysis in lymphocytes, macrophages and, in particular, in tumor cells. Both glycolysis and glutaminolysis provide metabolic intermediates for biosynthetic pathways: for example, glucose-6-phosphate for the formation of ribose-5-phosphate, and glutamine, ammonia and aspartate which are required for the synthesis of purine and pyrimidine nucleotides. However, the rates of both glycolysis and glutaminolysis are greatly in excess (>400-fold) of the requirements for the biosynthetic processes. If energy formation per se was the major reason for the high rate of glutamine utilization, why is the oxidation only partial? The ability of the cell to divide will require the synthesis of all the DNA, RNA, phospholipids, etc., at precise times in the cell cycle. Hence very high and accurate sensitivity of the processes that provide the precursors for these compounds to their specific regulators will be expected. Maintenance of high rates of glycolysis and glutaminolysis at all times can be seen therefore as a device to allow intermediates to be “tapped off” at the precise rate required whenever they are needed for biosynthesis. Maximal activities of some key enzymes of glycolysis, the tricarboxylic acid cycle and glutaminolysis from a variety of normal, neoplastic and suppressed cells are presented. The relative activities of hexokinase and 6-phosphofructokinase suggest that, particularly in neoplastic cells, in which the capacity for glucose transport is high, hexokinase could approach saturation in respect to intracellular glucose; consequently, hexokinase and phosphofructokinase could play an important role in the regulation of glycolytic flux in these cells. The activity of pyruvate kinase is considerably higher in tumorigenic cells than in nontumorigenic cells and higher in metastatic cells than in tumorigenic cells: for nontumorigenic cells the activities range from 28.4 to 574, for tumorigenic cells from 899 to 1280, and for metastatic cells from 1590 to 1627 nmol/min per mg of protein. The ratio of pyruvate kinase activity to 2 × phosphofructokinase activity is very high in neoplastic cells. The mean is 22.4 for neoplastic cells, whereas for muscle from 60 different animals it is only 3.8. Both citrate synthase and isocitrate dehydrogenase activities are present in nonneoplastic and neoplastic cells, suggesting that the full complement of tricarboxylic acid cycle enzymes is present in these latter cells. In neoplastic cells, the activity of glutaminase is similar to or greater than that of hexokinase, which suggests that glutamine may be as important as glucose for energy generation in these cells.

The effect of glutamine concentration on the activity of carbamoyl-phosphate synthase II and on the incorporation of [3H]thymidine into DNA in rat mesenteric lymphocytes stimulated by phytohaemagglutinin.

The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4% of the rate of glutamine utilization by lymphocytes. The Km of synthase II for glutamine is about 16 microM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 microM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the Km and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.

Rates of utilization of glucose, glutamine and oleate and formation of end-products by mouse peritoneal macrophages in culture.

1. The metabolism of mouse thioglycollate-elicited peritoneal macrophages was studied in culture for up to 96 h. 2. The rates of glycolysis, lactate formation and glutamine utilization were approximately linear with time for at least 80 h of culture. 3. The rates of glucose and glutamine utilization by cultured macrophages were approx. 500 and 90 nmol/h per mg of protein respectively. This rate of glucose utilization is at least 50% greater than that previously reported for macrophages during 60 min incubation in a shaking flask; and it is now increased by addition of glutamine to the culture medium. The rate of glutamine utilization in culture is similar to that previously reported for macrophages during 60 min incubation. The major end-product of glucose metabolism is lactate, and those of glutamine metabolism are CO2, glutamate, ammonia and alanine. 4. Oleate was utilized by these cells: 14C from [14C]oleate was incorporated into CO2 and cellular lipid. The highest rate of oleate utilization was observed when both glucose and glutamine were present in the culture medium. The presence of oleate in the culture medium did not affect the rates of utilization of either glucose or glutamine. Of the [14C]oleate incorporated into lipid, approx. 80% was incorporated into triacylglycerol and only 18% into phospholipid. 5. The turnover rate for the total ATP content of the macrophage in culture is about 10 times per minute: the value for the perfused isolated maximally working rat heart is 22. This indicates a high metabolic rate for macrophages, and consequently emphasizes the importance of the provision of fuels for their function in an immune response.

The effect of adenine nucleotides on the rate and fate of glutamine utilization by incubated mitochondria isolated from rat mesenteric lymph nodes.

The rate of glutamine utilization by isolated lymphocyte mitochondria is 21.4 nmol/min per mg protein, of which 72% is converted to glutamate. Addition of ATP, ADP or AMP increased the rate of glutamine utilization by 60%. Evidence is presented that this is due to a stimulation of oxoglutarate dehydrogenase activity by ADP: this may account for the stimulation of glutamine utilization by concanavalin A in lymphocyte.

Effect of palmitate, acetate and glucose on glutamine metabolism in Ehrlich ascites tumor cells

Acetate and the long chain free fatty acid palmitate provoked a decrease in the rates of glutamine utilization and glutamate production in Ehrlich ascites tumor cells incubated with 0.5 mM glutamine. There was a cumulative effect with glucose on glutamine metabolism.

Glutamine metabolism in isolated incubated adipocytes of the rat.

1. Phosphate-dependent glutaminase activity in the epididymal fat-pad was 15.1 nmol/min per mg of protein. Glutaminase activity demonstrated differences with respect to adipose-tissue sites. Considerable variation was found in different sites of adipose tissue from lean control and Zucker obese animals. 2. Adipocytes incubated in the presence of 2 mM-glutamine utilized glutamine at a rate of 1.8 mumol/h per g dry wt., and glutamate, ammonia, lactate and alanine were produced. Addition of glucose plus insulin increased the rates of glutamine utilization and glutamate, ammonia, lactate and alanine production. Isoprenaline alone or plus glucose further stimulated the rate of glutamine utilization and formation of end products. 3. The rate of incorporation of 14C from glutamine into CO2 was similar to that of glucose, but the rate of incorporation into triacylglycerol was much less. Addition of unlabelled glucose or glucose plus insulin stimulated the rate of incorporation of [14C]glutamine into triacylglycerol, but had no effect on that of 14CO2 formation. Isoprenaline plus glucose increased the rate of incorporation of [14C]glutamine into CO2, but decreased the rate of incorporation into triacylglycerol. 4. In the absence of insulin, the rate of [14C]glutamine incorporation into triacylglycerol was related to the glucose concentration (0-10 mM). However, in the presence of insulin, the rate of incorporation of [14C]glutamine was maximal at 1 mM-glucose.