Gln Concentrations Research Articles

Rumen-protected methionine fed to dairy cows: bioavailability and effects on plasma amino acid pattern and plasma metabolite and insulin concentrations.

An experiment was performed to compare the bioavailability of D,L-methionine (Met) of two rumen (polymer and fat)-protected Met forms (Smartamine; Rhône-Poulenc, Animal Nutrition, Antony, France and Mepron; Degussa AG, Hanau, Germany, respectively) fed once daily (at 0730 h) in amounts of 50 g per cow for 5 d. Six dairy cows were used in the crossover design. Blood samples were obtained from jugular veins 3 d before and 5 d after the start of Met supplementation at 1000, 1400, and 1800 h, and the three blood samples were pooled for analyses. Smartamine M feeding caused elevations of sulfur-containing amino acids (Met, Cys, and taurine) and reductions of Val and Ile and the total of branched-chain amino acids (Val + Leu + Ile). Mepron M85 feeding caused only a rise of Met concentrations. Concentrations of Met, taurine, and Gln were higher when Smartamine M than when Mepron M85 was fed. Concentrations of nonesterified fatty acids were reduced, and those of insulin were increased only by Mepron M85 feeding. Milk urea concentrations were lower in cows fed Mepron M85 than in controls, but milk yields; concentrations of fat, protein, and lactose; and somatic cell counts did not significantly change during the experiment and were not different between groups. Food intake, body weight, and body condition scores were not affected. In conclusion, only Mepron M85 supplementation influenced nonesterified fatty acids and insulin concentrations. However, the bioavailability of Met from Smartamine M was greater than of Mepron M85 and effects on other plasma-free amino acids were more marked. Whether less Met in the form of Smartamine M as Mepron M is needed to have the same effects on milk yield and composition needs to be investigated with doses used in practice.

Glutamine synthetase activity in Solanaceous cell suspensions accumulating alkaloids or not. 13C NMR and enzymatic assay

The metabolism of labelled pyruvate followed by 13C NMR and the measure of glutamine synthetase (GS) showed, according to previous results, a high activity of this enzyme in suspension cells of Nicotiana plumbaginifolia. This activity could derive glutamate from the alkaloid synthesizing pathways. However, a recent work showed that the rate of the GS gene transcription was inversely proportional to the Gln/Glu ratio. The measures of Gln and Glu concentrations in Nicotiana plumbaginifolia cells revealed that high GS activity correlates with the weak value of Gln/Glu ratio. Therefore, the hypothesis of GS dysfunctioning for the non-biosynthesis of alkaloids in N. plumbaginifolia suspension cells can be discarded. This conclusion is strengthened by the results obtained when using a GS inhibitor.

AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana: evidence for regulation by root glutamine levels.

The mechanisms involved in regulating high-affinity ammonium (NH4+) uptake and the expression of the AtAMT1 gene encoding a putative high-affinity NH4+ transporter were investigated in the roots of Arabidopsis thaliana. Under conditions of steady-state nitrogen (N) supply, transcript levels of the AtAMT1 gene and Vmax values for high-affinity 13NH4+ influx were inversely correlated with levels of N provision. Following re-supply of NH4NO3 to N-starved plants, AtAMT1 mRNA levels and 13NH4+ influx declined rapidly but remained high when the conversion of NH4+ to glutamine (Gln) was blocked with methionine sulfoximine (MSX). This result demonstrates that end products of NH4+ assimilation, rather than NH4+ itself, are responsible for regulating AtAMT1 gene expression. Consistent with this hypothesis, AtAMT1 gene expression and NH4+ influx were suppressed by provision of Gln alone, or together with NH4NO3 plus MSX. Furthermore, AtAMT1 transcript levels and 13NH4+ influx were negatively correlated with root Gln concentrations, following re-supply of N to N-starved plants. In addition to this level of control, the data suggest that high cytoplasmic [NH4+] may inhibit NH4+ influx.

Glycyl-Glutamine-Enriched Long-Term Total Parenteral Nutrition Attenuates Bacterial Translocation Following Small Bowel Transplantation in the Pig

Background.Improvements in immunosuppression, operative procedure, and posttransplant management have made clinical small bowel transplantation (SBT) feasible. Ischemia and reperfusion injury, total parenteral nutrition (TPN), and devoidment of enteral feeding lead to graft atrophy, gut barrier dysfunction, and bacterial translocation. Glutamine (Gln) is the principal fuel for the enterocyte. The influence of Gln dipeptide-supplemented TPN, especially long-term TPN, on intestinal graft permeability and bacterial translocation is not clear following SBT in the large animal model. Therefore, we studied the effect of glutamine dipeptide, glycyl-glutamine (Gly-Gln), on bacterial translocation following SBT in the pig, which has a physiology similar to humans.Materials and methods.The outbred pigs underwent segmental small bowel autotransplantation and were divided into two groups. In the STPN group (n= 5), the animal received standard TPN devoid of Gly-Gln for 28 days. In the GTPN group (n= 5), the animal received isonitrogenous (0.3 g/kg.day) and isocaloric (33 kcal/kg.day) TPN solution with 2% Gly-Gln for 28 days.Results.At the end of the experiment, Gly-Gln-enriched TPN could maintain the plasma Gln level, graft mucosal Gln and protein concentrations, and skeletal muscle Gln and protein concentrations. Gly-Gln-enriched TPN significantly decreased the bacterial number of mesenteric lymph nodes in the liver and spleen and intestinal permeability to99mTc-DTPA. There were no significant differences in body weight gain.Conclusions.The Gly-Gln–enriched long-term TPN may maintain the plasma Gln level, mucosal and muscle Gln, and protein concentrations and attenuate the intestinal permeability to99mTc-DTPA and bacterial translocation following small bowel transplantation in the pig.

Glutamine synthetase expression in rat lung is regulated by protein stability.

During physiological stress, the lung increases production of the amino acid glutamine (Gln) using the enzyme Gln synthetase (GS) to maintain Gln homeostasis. Glucocorticoid hormones are considered the principal mediators of GS expression during stress. However, whereas animal studies have shown that glucocorticoids increase lung GS mRNA levels 500-700%, GS activity levels rise only 20-45%. This discrepancy suggests that a posttranscriptional control mechanism(s) ultimately determines GS expression. We hypothesized that the level of GS protein in the lung is governed by the intracellular Gln concentration through a mechanism of protein destabilization, a feedback regulatory mechanism that has been observed in vitro. To test this hypothesis, Sprague-Dawley rats were treated with a Gln-free diet and the GS inhibitor methionine sulfoximine (MSO) to deplete tissue Gln levels and prevent this feedback regulation. Exposure to Gln-free chow and MSO (100 mg/kg body wt) for 6 days decreased plasma Gln levels 50% (P < 0.01) and decreased lung tissue Gln levels by 70% (P < 0.01). Although lung GS mRNA levels were not influenced by Gln depletion, there was a sevenfold (P < 0.01) increase in GS protein. A parenteral Gln infusion (200 mM, 1.5 ml/h) for the last 2 days of MSO treatment replenished lung Gln levels to 65% of control level and blunted the increase in GS protein levels by 33% (P < 0.05) compared with rats receiving an isomolar glycine solution. The acute effects of glucocorticoid and MSO administration on lung GS expression were also measured. Whereas dexamethasone (0.5 mg/kg) and MSO injections individually augmented lung GS protein levels twofold and fourfold (P < 0.05), respectively, the combination of dexamethasone and MSO produced a synergistic, 12-fold induction (P < 0.01) in lung GS protein over 8 h. The data suggest that, whereas glucocorticoids are potent mediators of GS transcriptional activity, protein stability greatly influences the ultimate expression of GS in the lung.

Are phloem amino acids involved in the shoot to root control of NO-3 uptake in Ricinus communis plants?

ments for growth and development (Glass, 1983; Clarkson, 1988; Rodgers and Barneix, 1988; Grignon, The putative role of phloem amino acids as negative feed- 1990; Imsande and Touraine, 1994). This seems to result back signals for root NO' uptake was investigated from changes in the expression of the various root uptake in Ricinus communis L. The NO' -grown plants were systems, which are specifically down-regulated under high subjected to N-deficiency due either to complete nutritional status of the plant for the corresponding ion N-deprivation, or to localized N-deprivation on one side or element (Clarkson and Luttge, 1991; Logan et al., of a split-root system. In comparison with controls, com- 1997). Little is known about the endogenous signals plete N-deprivation resulted in a transient increase in triggering this response, but a common hypothesis is that 15NO' influx, and in profound changes in downward root uptake systems are under negative feedback control phloem transport of amino acids. Total amino acid con- by the root concentration of the ion they take up (or of centration in the phloem sap decreased by 40%, but its metabolic products) (Glass, 1983, 1988; Clarkson, responses markedly differed between the individual 1988; Grignon, 1990; Lee et al., 1992). However, this is amino acids. Concentrations of Gln and Ser were rapidly not suYcient to account for all aspects of the control of lowered by 50%, while those of Val, Phe, Leu, and Ile root ion uptake. Indeed, numerous studies have demon- displayed a marked increase. Localized N-deprivation on strated that the regulatory mechanisms are not located in one side of the split root system also resulted in the the root only, but integrated at the whole plant level up-regulation of 15NO' influx in the roots still supplied (Clarkson, 1988; Pitman, 1988; Grignon, 1990; Imsande with NO' . However, the amino acid composition of the and Touraine, 1994). For instance, experiments with split- phloem sap directed to these roots was not modified by root plants showed that NO' 3 uptake by roots well the treatment, and remained similar to that in N-sufficient supplied with NO' 3 is de-repressed in response to

Glutamate transport and cellular glutamine metabolism: regulation in LLC-PK1 vs. LLC-PK1-F+ cell lines.

The glutamate (Glu) transporter may modulate cellular glutamine (Gln) metabolism by regulating both the rates of hydrolysis and subsequent conversion of Glu to alpha-ketoglutarate and NH+4. By delivering Glu, a competitive inhibitor of Gln for the phosphate-dependent glutaminase (PDG) as well as an acid-load activator of glutamate dehydrogenase (GDH) flux, the transporter may effectively substitute extracellularly generated Glu from the gamma-glutamyltransferase for that derived intracellularly from Gln. We tested this hypothesis in two closely related porcine kidney cell lines, LLC-PK1 and LLC-PK1-F+, the latter selected to grow in the absence of glucose, relying on Gln as their sole energy source. Both cell lines exhibited PDG suppression as the result of Glu uptake while disrupting the extracellular L-Glu uptake, with D-aspartate-accelerated intracellular Glu formation coupled primarily to the ammoniagenic pathway (GDH). Conversely, enhancing the extracellular Glu formation with p-aminohippurate and Glu uptake suppressed intracellular Gln hydrolysis while NH+4 formation from Glu increased. Thus these results are consistent with the transporter's dual role in modulating both PDG and GDH flux. Interestingly, PDG flux was actually higher in the Gln-adapted LLC-PK1-F+ cell line because of a two- to threefold enhancement in Gln uptake despite greater Glu uptake than in the parental LLC-PK1 cells, revealing the importance of both Glu and Gln transport in the modulation of PDG flux. Nevertheless, when studied at physiological Gln concentration, PDG flux falls under tight Glu transporter control as Gln uptake decreases, suggesting that cellular Gln metabolism may indeed be under Glu transporter control in vivo.

Oxygen supply dependence of urea production in the isolated perfused rat liver.

To determine whether hepatic urea production is limited at low hepatic O2 delivery (DO2) by O2 itself or by the availability of substrate for urea synthesis, we isolated livers from normal rats and perfused them with Krebs-Henseleit bicarbonate (KHB) buffer, KHB + 5 mM NH4Cl, or KHB + 5 mM glutamine (Gln) as an NH3 donor. The pump flow was lowered in stages, and we determined at each flow rate inflow and outflow O2 content and urea levels in the outflow perfusate. Urea production in Gln-perfused livers remained constant at high DO2 and declined in direct proportion to DO2 below a critical oxygen delivery (DO2crit, the point below which the hepatic O2 consumption [VO2] becomes limited by the hepatic DO2). The DO2crit calculated from the urea release-DO2 relationship (147 +/- 32 microl/min/dry g) was similar to the DO2crit calculated from the VO2-DO2 relationship (158 +/- 26 microl/min/dry g). When Gln concentration and flow rate were maintained constant while decreasing PO2 in the inflow perfusate (as well as hepatic DO2), urea production declined below the DO2crit. Furthermore, when Gln concentration in the perfusate was gradually reduced while keeping hepatic DO2 constant, urea production decreased proportionally with Gln concentrations in the perfusate. Consequently, urea production is dependent on Gln and O2 availability and becomes limited at the same DO2crit determined by the VO2-DO2 relationship.

A 15N GC/MS study of in vivo glutamine synthesis in liver failure rats.

To clarify the nature of nitrogen metabolism between branched chain amino acid (BCAA) and glutamine (Gln) in liver failure, we measured arterial plasma concentrations of Gln and 15N uptake to amino-N and amide-N of Gln in normal and D-galactosamine-induced fulminant hepatic failure (FHF) rats after 15N-leucine (Leu) injection. Fifteen, 30 and 60 min after Leu injection, the arterial plasma concentrations of Gln were significantly higher in FHF rats than in controls. The concentrations of amino-15N Gln were also significantly higher in FHF rats than in controls at 5, 15, 30 and 60 min after injection. The concentrations of amide-15N Gln did not significantly differ between FHF and controls at 5, 15 and 30 min. However, at 60 min, the concentration was significantly higher in the FHF rats. The higher uptake of 15N to amino-N of Gln in FHF rats suggests the presence of an enhanced ability to synthesize Gln from Leu in FHF rats. The higher uptake of 15N to amide-N of Gln in FHF rats at 60 min after injection suggests that excessive administration of BCAA to patients with severely impaired urea-cycle capacity suffering with hepatic failure may lead to greater levels of hyperammonemia.

Effect of Starch on the Bioavailability of Glutamine and Leucine in the Dairy Cow

This experiment was designed to quantify changes in utilization of Gln and Leu by the gut wall as a result of changes in the starch supply to the duodenum. Four dairy cows fitted with cannulas in the rumen and the distal duodenum were adapted for 3 wk to starch infusion, either into the rumen (600 g/d of flaked maize) or into the duodenum (300 g/d of flaked maize plus 300 g/d of maize meal), in a 2×2 crossover design. Absorption and elimination kinetics and the relative bioavailability of Gln and Leu were measured during wk 4 and 5. After infusion of 50g of Gln or 10g of Leu into the duodenum or jugular vein, blood samples were taken from the jugular vein at 0.5-h intervals up to 4h after infusion. Concentrations of Gln and Leu in plasma fitted best to an open, one-compartment model (duodenal infusion) or to an open, two-compartment model (i.v. infusion). Both amino acids were rapidly absorbed; half-life times were less than 20min. The amount of Gln trapped in the splanchnic bed was higher than the amount of Leu trapped in the splanchnic bed. Site of starch infusion did not affect the relative bioavailability of amino acids.

Activités métaboliques et toxicité du dinoflagellé Alexandrium tamarense en culture à dialyse exposée à un milieu estuarien

Metabolic activities and toxicity of the dinoflagellate Alexandrium tamarense were studied for a dialysis culture exposed to unenriched natural seawater and a batch culture grown in an enriched medium. The following observations were made on the dialysis culture compared with the batch culture: (i) Depending on the season period, the cell densities per litre were similar (≈ 10 × 106 – 14 × 106) or greater (66 × 106). (ii) During growth and stationary phases, cellular consumption of the nutrients (NO3− + NO2−) was much greater (5–50 times), (iii) During growth, the composition of the intracellular (IFAA) and extracellular dissolved free amino acid (EFAA) was characterized by the presence of ORN and LYS in the dialysis culture, which represent a substantial fraction of the IFAA pool of the dinoflagellate; a significant depletion of the IFAA was observed, but the recovery of Gln, Glu, and Arg cell concentration levels at the stationary phase was more important. (iv) During the growth phase, the maximum excretion rate of amino acids (fmol∙cell−1∙d−1) was 263 (in decreasing order of importance: Glu, Gin, Ser, Asp, Leu, Ala, G+T, and Orn) compared with 14,5. (v) During stationary phase, the reduction in excretion activity was twofold with Gln, Glu, Leu, and Orn while 9,2 fmol∙cell−1∙d−1 were observed in batch culture, (vi) Total toxin content was about 4 to 5 times higher (means: 95 and 75 fmol∙cell−1 during growth and stationary phases respectively), with greater concentrations in more potent derivates like saxitoxin and neosaxitoxin. This higher cell toxicity may be attributed to the particular growth conditions of the dialysis culture, which more closely approximate the natural environment, through diffusion processes involving a constant elimination of low molecular weight autoinhibitory metabolites and a more efficient nutrient uptake.Key words: Alexandrium tamarense, dinoflagellate, dialysis culture, phycotoxins, nitrogen metabolism.

Gut adaptation and the insulin-like growth factor system: regulation by glutamine and IGF-I administration.

Intestinal adaptation after extensive small bowel resection in rats is augmented by the provision of diets supplemented with the amino acid glutamine (Gln) or by administration of insulin-like growth factor-I (IGF-I). The goal of this study was to investigate potential synergistic effects of Gln and IGF-I on postresection ileal hyperplasia. Rats underwent 80% small bowel resection (SBR) and then were fed low-Gln or L-Gln-enriched diets and subcutaneously given recombinant human IGF-I or vehicle for 7 days. Gln and IGF-I each significantly enhanced adaptive ileal hyperplasia (DNA content) compared with rats receiving vehicle and low-Gln diet. Ileal DNA content was highest when IGF-I was administered together with Gln supplementation. Combined IGF-I plus Gln synergistically increased ileal weight and protein content. This was associated with higher plasma concentrations of IGF-I and Gln than observed when IGF-I or Gln was given individually. Ileal IGF-I mRNA expression rose nearly twofold during gut adaptation after SBR; this response was augmented with IGF-I administration but was unaltered by Gln feeding. In contrast, dietary Gln, but not IGF-I therapy, prevented a decrease in hepatic IGF-I mRNA induced by SBR. We conclude that parenteral IGF-I and enteral Gln have both individual and synergistic effects on ileal adaptation after massive small intestinal resection. These findings support the concept that specific gut-trophic nutrients and growth factors may be combined to enhance intestinal adaptation and possibly reduce the severity of short bowel syndrome after intestinal resection.

Effect of carnitine on decrease of branched chain amino acids and glutamine in serum of septic rats.

Blood concentrations of branched chain amino acids (BCAA; leucine, isoleucine, and valine) and glutamine (Gln) decrease markedly in sepsis. We investigated the effect of carnitine on serum concentrations of BCAA and Gln in fasted septic rats. Rats were made septic by cecal ligation and puncture. They developed extremely high blood concentrations of endotoxin, and serum concentrations of BCAA and Gln were markedly decreased 2 d after the operation. When L-carnitine was administered subcutaneously to the rats at 500 mg/kg body weight every 12 h for 2 d starting at the operation, no decrease in the serum concentrations of BCAA and Gln was observed. This indicates that the administration of carnitine can prevent the decrease of serum concentrations of BCAA and Gln in septic animals.

Free Amino Acids in Plasma and Muscle of High Yielding Dairy Cows in Early Lactation

Free AA in plasma and muscle were monitored in 36 dairy cows from 2 wk before until 15 wk after parturition. Cows were kept indoors and fed individually. The AA concentrations in plasma from 6 to 15 wk of lactation were compared with precalving concentrations. Plasma concentrations of Met, Phe, Glu, and Gln decreased by 16, 24, 25, and 25%, respectively. The ranking of the essential AA according to their decrease in plasma corresponded to the order in which they generally appear to be limiting for milk protein synthesis. The decrease of Glu and Gln in plasma exceeded that of the essential AA and contrasted strongly with all other nonessential AA. The change in the AA profile in muscle from pregnancy to lactation resembled that described for the catabolic state in mammals and suggests that muscle protein was degraded for supply of AA to the udder, despite excess protein and energy supply 15 wk into lactation. In muscle, the decrease in the pool of free Gln exceeds 25% and is higher than for any other AA. These observations support our hypothesis that Gln is potentially limiting for milk protein synthesis in the high yielding dairy cow.

Microdialysis with high NaCl causes central release of amino acids and dopamine.

Recent studies have shown that the neuropeptides arginine-8-vasopressin (AVP) and oxytocin (OXT) are released within the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus in response to microdialysis of these nuclei with high-NaCl perfusion media. These results suggest an inherent osmosensitivity of SON and PVN neurons. To investigate whether the observed release of AVP/OXT is a unique phenomenon to these neuropeptides, several brain regions were examined for the release of amino acids or dopamine in response to high- or low-NaCl stimulation. Urethane-anesthetized male Sprague-Dawley rats were perfused with five-ion solution using U-shaped microdialysis probes. Samples were collected at 30-min intervals and analyzed for amino acids and dopamine by HPLC. In the dialysates of all perfusion areas, including the SON, PVN, hippocampus, and striatum, concentrations of Asp, Glu, Ser, Gln, Gly, taurine (Tau), and gamma-aminobutyric acid (GABA) were significantly increased during perfusion with high-NaCl medium. This release was found to be dose dependent when tested in the hippocampus and striatum with perfusion medium containing 0.5 or 1.0 M NaCl. However, only the release of Glu and Ser was found to be Ca2+ dependent. In contrast, the use of mannitol, a nonionic osmolyte, for perfusions in the striatum in concentrations of 0.5 and 1 M resulted in reduced levels of amino acids in the dialysates (Glu, Ser, Gln, and Tau). Low-NaCl perfusion medium (0.01 M) resulted in significantly increased Glu, Tau, Gly, and GABA levels in the striatum. In addition, dopamine levels in striatal dialysates were significantly increased during stimulation with 1 M NaCl. These results indicate that stimulation with high NaCl concentrations affects the release of several neurotransmitters and is not specific for AVP and OXT. The described phenomenon of the release of amino acids in response to this stimulation seems to be a response to the changed ionic concentration rather than to the osmolality. In light of these findings shown for amino acids and dopamine as well as those previously reported for AVP, OXT, and angiotensin, it would appear that sensitivity to tonicity changes brought about by microdialysis may be a feature of many transmitter systems.

La sous-alimentation énergétique et/ou azotée chez la vache tarie. Effets sur les acides gras volatils du rumen, quelques métabolites et hormones du plasma et l'excrétion urinaire de la 3-méthylhistidine

In order to study the effects of a nitrogenous and/or energetic underfeeding on some metabolites and hormones, 4 dry cows were fed in 2 equal daily meals with hay-based rations. Four rations were distributed. They supplied too much (HN) or too little (LN) digestible protein in the small intestine and too much (HE) or too little (LE) net energy, ie the diets were HN-HE, HN-LE, LN-HE, and LN-LE. Continuous collection of rumen liquor samples (volatile fatty acids or VFA determination), venous blood samples (amino acids (alanine Ala, glutamine Gln, glycine Gly and serine Ser), urea, glucose, insulin and growth hormone (GH) measurements) and urine samples (determination of the amount of 3-methylhistidine 3-MeHi excreted) was carried out for 24 consecutive hours. By comparison with the reference diet (HN-HE), underfeeding was accompanied by a reduction in ruminal VFA concentrations, an increase in those of plasma Gly and GH, and a maintenance of glycemia levels. Furthermore, nitrogenous and energetic underfeeding (LN-LE) was accompanied by a decrease in plasma Ala, Gln and insulin concentrations. Nitrogenous underfeeding (LN-HE) caused a decrease in uremia levels, an increment in those of serinemia and no variation in circulating insulin concentrations. The energetic underfeeding (HN-LE) was accompanied by a reduction in insulinemia levels and an increase in those of alaninemia and serinemia. Such changes suggest that dry cattle adapt to underfeeding by mobilizing endogenous proteins. However, only the 2 diets with reduced energetic supplies were accompanied by an increase (P < 0.05) in the amount of the urinary 3-MeHi excreted per 24 h, suggesting that the level of energy in the diet is the main trigger for protein mobilization. Finally, the study of the 24-h evolution of the parameters revealed the influence of the feeding time (morning or evening) and the level of the dietary nitrogen and energy supplied on the variation in their concentration.

Glutamine supplementation prevents the decrease of mitogen response after a treadmill exercise in rats.

The effect of glutamine (Gln)-supplemented diet on mitogen response decreased immediately after a treadmill exercise was examined by measuring the proliferations of peripheral blood lymphocytes (PBL) with phytohemagglutinin (PHA) and concanavalin A (ConA) in male Fisher rats. Although the plasma Gln concentration was significantly decreased in the control group immediately after a treadmill exercise (20 m/min, 60 min) compared to rested rats, plasma Gln concentration of rats fed Gln-supplemented diet for 3 weeks was significantly higher than that of control group in resting and was not significantly decreased even immediately after a treadmill exercise. In addition, proliferation of PBL with PHA or ConA and interleukin 2 (IL2) production were also significantly decreased immediately after a treadmill exercise in control group. On the contrary, their functions were almost maintained in Gln-supplemented group even immediately after a treadmill exercise. PBL from rats fed Gln-supplemented diet showed a higher response to mitogens such as PHA and ConA compared to the control group. Furthermore, their PBL showed higher incorporation of [3H]Gln compared to that of the control group irrespective of treadmill exercise. These results indicate that the preventive effect of Gln-supplemented diet on mitogen response decreased after a treadmill exercise is due to an increased response to mitogen and increased uptake of Gln as sources of fuel and nucleotides to the immune cells.

Harry M. Vars Research Award. Glutamine enhances immunoregulation of tumor growth.

It is known that tumor progression is associated with a depletion in host glutamine (Gln) stores and a depression of natural killer (NK) cell activity. After demonstrating an in vitro dependence of NK cell activity on Gln and glutathione concentration, this study evaluated the effects of oral Gln on Gln and glutathione metabolism, NK cell activity, and tumor growth in the tumor-bearing rat. Two days before tumor implantation, rats (n = 32) were randomized to receive Gln (1 g/kg/d) or an isonitrogenous amount of glycine by gavage and pair-fed food. On day 21 after tumor implantation, rats were killed, and tumors were measured and processed for glutaminase activity, glutathione content, and tumor morphometrics. Splenic lymphocytes were assayed for NK cell activity via a chromium (51Cr) release assay using YAC (NK-cell-sensitive mouse tumor cell line) target cells. Blood Gln and glutathione were measured. A second set of rats (n = 16) were treated similarly except that ketamine was given twice weekly to suppress NK cell activity. During the 3-week study period, tumor growth was decreased by 40% in the Gln group. This decrease in growth was associated with a 30% increase in NK cell activity. Administration of ketamine to rats completely reversed the higher NK cell activity and decreased the tumor growth seen in the Gln-treated group. These data indicate that oral Gln supplementation, through support of host Gln stores and glutathione production, may decrease tumor growth by enhancing NK cell activity.

Release of amino acids into regional superfusates of the spinal cord by mechano-stimulation of the reproductive tract

Based on pharmacological evidence that inhibitory amino acids mediate vaginocervical mechano-stimulation produced analgesia (VSPA), we hypothesized that inhibitory amino acids would be released endogenously in the spinal cord in response to vaginocervical mechano-stimulation (VS). This hypothesis was tested by HPLC analysis of the amino acid content of 5-min superfusates of the spinal cord before, during and after VS (400 g force applied against the cervix) in urethane-anesthetized rats. Utilizing an in vivo push-pull superfusion method, artificial cerebrospinal fluid was continuously superfused over the spinal cord through the intrathecal space surrounding the sacral-lower thoracic region. In addition, concentrations of amino acids in the superfusate were measured in response to KCl stimulation (increasing the superfusion medium from 3.4 to 40.0 mM KCl to produce non-specific depolarization), and to noxious hind paw mechano-stimulation (pinching the hind paw to produce a sustained flexor response in ipsilateral hind leg). There was a significant increase in the concentration of Gly, Tau, Asp, Glu and Lys in the superfusate in response to VS ( n = 8) and to KCl ( n = 8), but not to hind paw stimulation ( n = 5). Also, GABA concentrations increased in response to KCl, and the concentration of Ala, Ser, Gln, Thr, Arg and Phe increased in response to VS, however, GABA levels were sometimes below the limits of detection. In contrast, there was no significant change in any amino acid concentration in response to hind paw pinch stimulation, and VS did not significantly affect the concentrations of Tyr, His, Ile, Leu, Met, Trp or Val. The present findings support our hypothesis that VS releases inhibitory amino acids in the spinal cord. Moreover, other amino acids, including ‘excitatory’ amino acids, are released into the superfusate. The profile of amino acid release in response to VS differs from that in response to paw pinch or KCl administration.

The use of a glutamine-enriched enteral feeding in the treatment of malabsorption and diarrhea in an infant with hypoalbuminemia

Hypoalbuminemia leads to a cascade of biochemical and physiological alterations with severe consequences to intestinal mucosa integrity and subsequent malabsorption. Enteral refeeding regimens are limited by the persistent malabsorption that occurs secondary to villus atrophy associated with malnutrition. Total parenteral nutrition (TPN), which imparts independent risks to the malnourished immunocompromised patient, is often used to meet protein and energy requirements. It has been suggested that exclusive TPN therapy is less than optimal in the treatment of malabsorption since commercially available TPN solutions are void of glutamine (Gln) which becomes a conditionally essential amino acid during stress and serves as the primary respiratory fuel for enterocytes. Newly developed Gln enriched enteral formulas (EF) for adults have been recommended in stress and trauma to minimize protein catabolism, enhance plasma and cellular Gln, and promote intestinal repair. The use of a Gln enriched EF in pediatrics has not been documented. We report our experience with a 19 month old male admitted with hypoalbuminemia (1.8 g/dl [nl 3.7 – 5.7 gms/dl]), diarrhea, and decreased growth velocity who was treated with intravenous albumin and a clear liquid diet with oral rehydration solution (Pedialyte) for 7 days without cessation of excessive stool output. TPN was initiated and on two occasions during 8 days of therapy oral feedings were attempted unsuccessfully. Continuous nasogastric feeds of strength Gln enriched EF (Alitraq) were initiated at 10 ml/hr and progressed to 45 ml/hr concurrent with TPN to provide exogenous glutamine and promote intestinal mucosal regeneration. Plasma amino acids were determined at baseline and 12, 24, 48 hr. Alitraq feedings were well tolerated without emesis or diarrhea, and TPN was discontinued and oral feedings advanced rapidly including lactose which is usually not well tolerated following gastrointestinal insult. Plasma amino acids were normal with Gln concentration maintained at 625–697 umol/l [nl 100–704 umol/l] indicating adequate exogenous Gln. Serum albumin at discharge was 5.2 g/dl. This experience demonstrated the usefulness of a Gln enriched EF in the treatment of a child with malabsorption and diarrhea and suggests the need for a glutamine enriched pediatric EF.