Metabolic interactions between restraint stress and <Emphasis Type="SmallCaps">l</Emphasis>-lysine: The effect on urea cycle components

Summary.  We studied the effects of l-lysine on wrap-restraint stress-induced changes in ureagenesis. An exposure to wrap-restraint stress did not affect the plasma concentration of l-lysine, but did decrease plasma urea and arginine. Oral l-lysine (1 g/kg) blocked the effect of stress on ureagenesis, and enhanced the effect of stress on l-arginine. No influence of l-lysine were found in controls. The results imply a stress-specific, ureagenesis-stimulating effect of l-lysine, and suggest an increased requirement for l-arginine during the above conditions. Received December 9, 2002 Accepted January 21, 2003 Published online April 3, 2003 Acknowledgement Authors thank Dr. M. Miura (Ajinomoto Co.) for his help with amino acid analysis and Dr. T. Kimura (Ajinomoto Co.) for discussions on amino acid metabolism. Authors' address: Dr. M. Smriga, Ajinomoto Co. Inc., Institute of Life Sciences, 1-1 Suzuki-cho, 210-8681 Kawasaki, Japan, Fax +81-44-210-5893, E-mail: miroslav_smriga@ajinomoto.com Abbreviations: Arg, l-arginine; Orn, l-ornithine; Lys, l-lysine; p.o., oral; WRS, wrap-restraint stress     

Adaptative increase of ornithine production and decrease of ammonia metabolism in rat colonocytes after hyperproteic diet ingestion

Chronic high-protein consumption leads to increased concentrations of NH(4)(+)/NH(3) in the colon lumen. We asked whether this increase has consequences on colonic epithelial cell metabolism. Rats were fed isocaloric diets containing 20 (P20) or 58% (P58) casein as the protein source for 7 days. NH(4)(+)/NH(3) concentration in the colonic lumen and in the colonic vein blood as well as ammonia metabolism by isolated surface colonic epithelial cells was determined. After 2 days of consumption of the P58 diet, marked increases of luminal and colonic vein blood NH(4)(+)/NH(3) concentrations were recorded when compared with the values obtained in the P20 group. Colonocytes recovered from the P58 group were characterized at that time and thereafter by an increased capacity for l-ornithine and urea production through arginase (P < 0.05). l-Ornithine was mostly used in the presence of NH(4)Cl for the synthesis of the metabolic end product l-citrulline. After 7 days of the P58 diet consumption, however, the ammonia metabolism into l-citrulline was found lower (P < 0.01) when compared with the values measured in the colonocytes recovered from the P20 group despite any decrease in the related enzymatic activities (i.e., carbamoyl-phosphate synthetase I and ornithine carbamoyl transferase). This decrease was found to coincide with a return of blood NH(4)(+)/NH(3) concentration in colonic portal blood to values close to the one recorded in the P20 group. In response to increased NH(4)(+)/NH(3) concentration in the colon, the increased capacity of the colonocytes to synthesize l-ornithine is likely to correspond to an elevated l-ornithine requirement for the elimination of excessive blood ammonia in the liver urea cycle. Moreover, in the presence of NH(4)Cl, colonocytes diminished their synthesis capacity of l-citrulline from l-ornithine, allowing a lower cellular utilization of this latter amino acid. These results are discussed in relationship with an adaptative process that would be related to both interorgan metabolism and to the role of the colonic epithelium as a first line of defense toward luminal NH(4)(+)/NH(3) concentrations.     

Effect of l-arginine on metabolism of polyamines in rat’s brain with extrahepatic cholestasis

Cholestatic encephalopathy results from accumulation of unconjugated bilirubin and hydrophobic bile acids in the brain. The aim of this study was to determine disturbances of polyamine metabolism in the brains of rats with experimental extrahepatic cholestasis and the effects of l-arginine administration. Wister rats were divided into groups: I: sham-operated, II: rats treated with l-arginine, III: animals with bile-duct ligation (BDL), and IV: cholestatic-BDL rats treated with l-arginine. Increased plasma γ-glutamyltransferase and alkaline phosphatase activity and increased bile-acids and bilirubin levels in BDL rats were reduced by administration of l-arginine (P < 0.001). Cholestasis increased the brain’s putrescine (P < 0.001) and decreased spermidine and spermine concentration (P < 0.05). The activity of polyamine oxidase was increased (P < 0.001) and diamine oxidase was decreased (P < 0.001) in the brains of BDL rats. Cholestasis increased the activity of arginase (P < 0.05) and decreased the level of citrulline (P < 0.001). Administration of l-arginine in BDL rats prevents metabolic disorders of polyamines and establishs a neuroprotective role in the brain during cholestasis.     

Characteristics of dipeptide transport in pig jejunum in vitro

 Characteristics of dipeptide transport in pig jejunum were investigated in vitro by applying the Ussing-chamber technique and mucosal uptake studies. Addition of both glycyl-l-glutamine and glycyl-l-sarcosine (20 mmol · l⁻¹) to the mucosal buffer solution significantly increased the short-circuit current by 2.60 ± 0.15 and 1.57 ± 0.20 μeq · cm⁻² · h⁻¹, respectively. Concentration-dependent changes in short-circuit current followed Michaelis-Menten kinetics with similar affinity constants for both dipeptides. From unidirectional flux rates for radiolabelled glycyl-l-sarcosine, a net flux rate for glycyl-l-sarcosine of 49.8 ± 6.7 nmol · cm⁻² · h⁻¹ was calculated. In mucosal uptake experiments, the apical influx of ¹⁴C-labelled glycyl-l-sarcosine into isolated porcine mucosa was pH dependent and significantly inhibited by glycyl-l-glutamine. Moreover, RT-PCR studies with primers derived from rabbit PepT1 identified two PCR fragments of identical size to rabbit PepT1 from pig intestinal mRNA preparations. In conclusion, our studies revealed key features of mammalian intestinal peptide transporters and give evidence for a PepT1-like transporter in the pig jejunum that could significantly contribute to the overall amino acid absorption from the gut. Accepted: 30 June 1999     

Transport of glutamine inXenopus laevis oocytes: Relationship with transport of other amino acids

Summary We have investigated transport of the amino acid glutamine across the surface membranes of prophase-arrestedXenopus laevis oocytes. Glutamine accumulation was linear with time for 30 min; it was stereospecific with aK _m of 0.12±0.02mm andV _max of 0.92±0.17 pmol/oocyte · min forl-glutamine. Transport ofl-glutamine was Na⁺-dependent, the cation not being replaceable with Li⁺, K⁺, choline, tris(hydroxymethyl)-aminomethane (Tris), tetramethylammonium (TMA) or N-methyld-glucamine NMDG); external Cl^– appeared to be necessary for full activation of Na⁺-dependent glutamine transport. Two external Na⁺ may be required for the transport of one glutamine molecule.l-glutamine transport (at 50 m glutamine) was inhibited by the presence of other amino acids:l-alanine,d-alanine,l-leucine,l-asparagine andl-arginine (about 60% inhibition at 1mm);l-histidine,l-valine and glycine (25 to 40% inhibition at 1mm);l-serine,l-lysine,l-phenylalanine andl-glutamate (45 to 55% inhibition at 10mm). N-methylaminoisobutyric acid (meAIB) had no effect at 10mm, but 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) inhibited Na⁺/glutamine transport by about 50% at 10mm.l-glutamine was a competitive inhibitor of the Na⁺-dependent transport ofl-alanine,d-alanine andl-arginine; this evidence is consistent with the existence of a single system transporting all four amino acids. Glutamine uptake in oocytes appears to be catalyzed by a transport system distinct from the cotransport Systems A, ASC, N and Gly, although it resembles System B^0,+.     

Utilization ofd-amino acids byFusobacterium nucleatum andFusobacterium varium

Summary The utilization ofd- andl -amino acids with acidic, basic or polar side chains was demonstrated by HPLC. Two species of the anaerobeFusobacterium utilized D-lysine and the L isomers of glutamate, glutamine, histidine, lysine and serine. OnlyF. varium usedl-arginine,d-glutamate andd-serine as substrates, whereasF. nucleatum specifically utilizedd-histidine andd-glutamine.d-Glutamate accumulated in F. nucleatum cultures supplemented withd-glutamine, and ornithine was detected when eitherdl- orl-arginine was included inF. varium cultures. Based on literature precedents,d-glutamate andd-histidine are isomerized to their L isomers prior to degradation, but separate catabolic pathways are possible for each enantiomer of lysine and serine.     

Utilization of amino acids by bacteria from the pig small intestine

This study determined the utilization of amino acids (AA) by bacteria from the lumen of the pig small intestine. Digesta samples from different segments of the small intestine were inoculated into media containing 10 mmol/L each of select AA (l-lysine, l-threonine, l-arginine, l-glutamate, l-histidine, l-leucine, l-isoleucine, l-valine, l-proline, l-methionine, l-phenylalanine or l-tryptophan) and incubated for 24 h. The previous 24-h culture served as an inoculum for a subsequent 24-h subculture during each of 30 subcultures. Results of the in vitro cultivation experiment indicated that the 24-h disappearance rates for lysine, arginine, threonine, glutamate, leucine, isoleucine, valine or histidine were 50–90% in the duodenum, jejunum or ileum groups. After 30 subcultures, the 24-h disappearance rates for lysine, threonine, arginine or glutamate remained greater than 50%. The denaturing gradient gel electrophoresis analysis showed that Streptococcus sp., Mitsuokella sp., and Megasphaera elsdenii-like bacteria were predominant in subcultures for utilizing lysine, threonine, arginine and glutamate. In contrast, Klebsiella sp. was not a major user of arginine or glutamate. Furthermore, analysis of AA composition and the incorporation of AA into polypeptides indicated that protein synthesis was a major pathway for AA metabolism in all the bacteria studied. The current work identified the possible predominant bacterial species responsible for AA metabolism in the pig small intestine. The findings provide a new framework for future studies to characterize the metabolic fate of AA in intestinal microbes and define their nutritional significance for both animals and humans.     

Indicators of l-arginine metabolism and cardiovascular risk factors A cross-sectional study in healthy middle-aged men

Summary. This study examines the relationship between traditional risk factors of coronary artery disease and indicators involved in the metabolism of l-arginine (plasma and urine l-arginine, plasma l-citrulline, serum creatinine and urine orotic acid). Our study population consisted of 40 healthy male volunteers aged between 35 and 55 years. We found an inverse association between serum creatinine and blood pressure, between plasma l-citrulline and blood pressure, as well as between urine l-arginine and blood pressure. We also found a positive association between plasma LDL-cholesterol and urine l-arginine and a negative correlation between plasma l-arginine and LDL-cholesterol. Orotic acid measured from urine was not associated with any of the indicators of l-arginine metabolism. Our results indicate that l-arginine metabolism is of profound significance for cardiovascular health. However, our study does not answer questions relating to causality. Further studies are needed to clarify the causal relationship between cardiovascular risk factors, especially elevated blood pressure and high LDL-cholesterol, and indicators of l-arginine metabolism. Received January 18, 1999     

Heterologous and homologous expression of the arginine biosynthetic argC~H cluster from Corynebacterium crenatum for improvement of (L) -arginine production

The genes involved in l-arginine biosynthesis in Corynebacterium crenatum are organized as the argCJBDFRGH cluster like in Corynebacterium glutamicum. However, the argC~H cluster of the C. crenatum SYPA 5-5, which is an industrialized l-arginine producer, had a lethal mutation occurring in the ArgR repressor encoding gene. The argC~H cluster with an inactive argR was overexpressed in E. coli and C. crenatum. In the recombinant E. coli JM109 enzyme activities were increased, and more l-arginine was found in the supernatants from l-glutamine. When the argC~H cluster was overexpressed in C. crenatum under its native promoter Parg, l-arginine production was increased by 24.9%, but the presence of the recombinant plasmid pJC-9039 had a negative effect on cell growth. Surprisingly, the DO value of the recombinant strain dropped gently and stayed at a lower level from 24 h to the end of fermentation. The results demonstrated an increasing utilization of oxygen and the distinct enhancement of unit cell l-arginine yields with the cluster argC~H-bearing in C. crenatum SYPA-9039. This study provides a kind of Corynebacteria with improved l-arginine-producing ability and an efficient elevation for producing amino acid. Moreover, the promoter Parg would be used as a valid promoter to express objective genes for metabolic engineering in Corynebacteria.     

Comparative capacities of the pig colon and duodenum for luminal iron absorption

Iron deficiency is the most common human nutritional disorder in the world. Iron absorptive capacity of the small intestine is known to be much limited and therefore large quantities of iron salts must be used to treat iron deficiency. As a result, significant amounts of iron may reach the large intestine. This study compared the capacities of the small and large intestine to transfer luminal iron to the venous blood in relationship with the expression in epithelial cells of proteins involved in iron absorption using a pig model. Intracaecal injection of iron sulphate corresponding with 2.5 and 5.0 mg elemental iron per kg body mass resulted in modest, transient, but significant (p<0.05) increases in iron concentration in the portal blood plasma. By comparing portal blood plasma iron concentrations following injection in the duodenal and caecal lumen, we calculated that 5 h after injection, iron colonic absorption represented approximately 14% of duodenal absorption. Caecal and proximal colon mucosa accumulated iron to a much lower extent than the duodenal mucosa. Isolated colonocytes were found to express divalent metal transporter (DMT1) and ferritin, but to a lesser extent than the duodenal enterocytes. Ferroportin was highly expressed in colonocytes. In these cells as well as in enterocytes ferroportin was found to be glycosylated. In short term experiments and at a concentration in the range of that measured in the aqueous phases recovered from the large intestine luminal content after iron injection, iron sulphate did not alter colonocyte viability. We concluded that the colonic epithelial cells that express proteins involved in iron absorption are able to transfer luminal iron to the venous blood even if its relative participation in the overall intestinal absorption appears to be modest under our experimental conditions.     

Stability and inhibition of anaerobic processes caused by insufficiency or excess of ammonia nitrogen

Ammonia increases buffer capacity of methanogenic medium in mesophilic anaerobic reactor thus increasing the stability of anaerobic digestion process. Optimal ammonia concentration ensures sufficient buffer capacity while not inhibiting the process. It was found out in this paper that this optimum depends on the quality of anaerobic sludge under investigation. The optimal concentrations for methanogens were 2.1, 2.6 and 3.1 g/L of ammonia nitrogen in dependence on inoculum origin. High ammonia nitrogen concentration (4.0 g/L) inhibited methane production, while low ammonia nitrogen concentration (0.5 g/L) caused low methane yield, loss of biomass (as VSS) and loss of the aceticlastic methanogenic activity. It was found out that negative effect of low ammonia nitrogen concentration on biomass is caused not only by low buffer capacity but also by insufficiency of nitrogen as nutrient. It was also found out that anaerobic sludge with higher ammonia nitrogen concentration (4.2 g/L) tolerates even concentration of volatile fatty acids (160 mmol/L) which causes inhibition of the process with low ammonia nitrogen concentration (0.2 g/L).     

Microbial production of L -glutamate and L -glutamine by recombinant Corynebacterium glutamicum harboring Vitreoscilla hemoglobin gene vgb

Vitreoscilla hemoglobin (VHb) gene vgb equipped with a native promoter Pvgb or a tac promoter Ptac was introduced into Corynebacterium glutamicum ATCC14067, respectively. Ptac was proven to be more suitable for expressing VHb protein in higher concentration in both Escherichia coli and C. glutamicum strains compared with the native vgb promoter Pvgb. VHb-expressing C. glutamicum exhibited higher oxygen uptake rate and enhanced cell growth. Recombinant C. glutamicum harboring vgb gene equipped with Ptac promoter produced 23% more l-glutamate in shake-flask culture and grew to 30% more cell density and formed 22% more l-glutamate in fermentor studies compared with the wild-type strain. When a site-directed mutagenesis in which Tyr405 was replaced by a phenylalanine residue (Y405F) was performed on glutamine synthesis gene, recombinant C. glutamicum overexpressing the mutated gene glnA′ was able to produce l-glutamine effectively. Co-expression of vgb and glnA′ genes in C. glutamicum produced 17 g/l l-glutamine in shake flask culture, approximately 30% more than that produced by the recombinant harboring only glnA′ gene. In fermentor cultivation, the recombinant yielded 25% more cells and produced 40.5 g/l l-glutamine. In this study, it was clearly demonstrated that VHb significantly enhanced cell growth, l-glutamate, and l-glutamine production by recombinant C. glutamicum.     

Production and properties of asparaginase from a new Erwinia sp

Asparaginase production by a mesophilic strain ofErwinia sp. was examined; the maximum of activity was found at 40°C and pH 8.5. Among the various carbon sources, mannitol was shown to be the best for production of activity. Inorganic nitrogen sources were better than the organic ones. The enzyme activity was not inhibited by 10 mmol/L metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Co²⁺, Ni²⁺, Zn²⁺); the activity was strongly inhibited by addition of EDTA.l-Arginine,dl-alanine,l-asparagine andl-glutamine stimulated thel-asparaginase production by 3.9, 1.7, 4.3 and 4.0 fold, respectively. The combination ofl-arginine,l-asparagine andl-glutamine synergistically stimulated the asparaginase up to 5.8 fold.     

Dietary arginine supplementation enhances antioxidative capacity and improves meat quality of finishing pigs

The present study was conducted to test the hypothesis that dietary arginine supplementation may improve meat quality of finishing pigs. Beginning at ~60 kg body weight, pigs were fed a corn- and soybean meal-based diet supplemented with 0, 0.5 or 1% l-arginine until they reached a body weight of ~110 kg. On the last day of the experiment, pigs were food-deprived for 16 h before blood samples were obtained for analysis of amino acids, insulin, and other metabolites. Immediately thereafter, pigs were slaughtered for determination of carcass composition, muscle biochemical parameters, and meat quality. The result showed that arginine did not affect pig growth performance or carcass traits. However, 1% arginine decreased drip loss of pork muscle at 48 h postmortem, while increasing intramuscular fat content (P < 0.05). Supplementing 0.5 or 1% arginine to the diet increased arginine concentration and decreased cortisol level in serum, while enhancing antioxidative capacity and glutathione peroxidase activity in serum (P < 0.05). Additionally, 1% arginine increased antioxidative capacity in skeletal muscle (P < 0.05). Furthermore, 0.5 or 1% arginine decreased the cortisol receptor mRNA level in muscle (P < 0.05). Collectively, these results indicate that supplemental arginine improved meat quality and attenuated oxidative stress of finishing pigs.     

Asymmetric dimethylarginine in children with homocystinuria or phenylketonuria

Plasma concentration of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis from l-arginine and a cardiovascular risk factor, was found to be elevated in plasma of homocysteinemic adults. Enhanced cardiovascular risk due to homocystinuria and impaired renal function has been found in patients with phenylketonuria (PKU) on protein-restricted diet. However, it is still unknown whether ADMA synthesis is also elevated in children with homocystinuria due to cystathionine beta-synthase deficiency (classical homocystinuria), and whether ADMA may play a role in phenylketonuria in childhood. In the present study, we investigated the status of the l-arginine/NO pathway in six young patients with homocystinuria, in 52 young phenylketonuria patients on natural protein-restricted diet, and in age- and gender-matched healthy children serving as controls. ADMA in plasma and urine was determined by GC–MS/MS. The NO metabolites nitrate and nitrite in plasma and urine, and urinary dimethylamine (DMA), the dimethylarginine dimethylaminohydrolase (DDAH) metabolite of ADMA, were measured by GC–MS. Unlike urine ADMA excretion, plasma ADMA concentration in patients with homocystinuria was significantly higher than in controls (660 ± 158 vs. 475 ± 77 nM, P = 0.035). DMA excretion rate was considerably higher in children with homocystinuria as compared to controls (62.2 ± 24.5 vs. 6.5 ± 2.9 μmol/mmol creatinine, P = 0.068), indicating enhanced DDAH activity in this disease. In contrast and unexpectedly, phenylketonuria patients had significantly lower ADMA plasma concentrations compared to controls (512 ± 136 vs. 585 ± 125 nM, P = 0.009). Phenylketonuria patients and controls had similar l-arginine/ADMA molar ratios in plasma. Urinary nitrite excretion was significantly higher in phenylketonuria as compared to healthy controls (1.7 ± 1.7 vs. 0.7 ± 1.2 μmol/mmol creatinine, P = 0.003). Our study shows that the l-arginine/NO pathway is differently altered in children with phenylketonuria and homocystinuria. Analogous to hyperhomocysteinemic adults, elevated ADMA plasma concentrations could be a cardiovascular risk factor in children with homocystinuria. In phenylketonuria, the l-arginine/NO pathway seems not be altered. Delineation of the role of ADMA in childhood phenylketonuria and homocystinuria demands further investigation.     

Inhibitory action of serine on growth of bacteria of the genusBacillus on mineral synthetic media

l-Serine added to minimal synthetic media stops the growth ofBacillus subtilis, B. megaterium, B. mycoides andB. pantothenticus. All tested subspecies ofBacillus thuringiensis appear resistant to this amino acid. Serine acts bacteriostatically onB. subtilis strain B 003 and this effect depends on the concentrations of both the amino acid and the plated bacterium. Growth of serine-sensitiveBacillus strains can be restored by simultaneous addition of some other amino acids (e.g. l-threonine,l-arginine,l-aspartate orl-alanine) to the minimal media. This alleviating effect depends on the kind of amino acid. Some amino acids (e.g. l-threonine,l-tyrosine orl-tryptophan) are only effective when the serine concentration is not higher than 125 μmol/L, others (l-arginine,l-proline,l-alanine,l-aspartate orl-glutamate) are effective even when the serine concentration is as high as 500 μmol/L.     

Mechanism of the suppression against <Emphasis Type="SmallCaps">d</Emphasis>-galactosamine-induced hepatic injury by dietary amino acids in rats

To elucidate the mechanism by which dietary amino acids suppress the d-galactosamine (d-GalN)-induced hepatitis, we examined the involvement of Kupffer cells, tumor necrosis factor-α (TNF-α) and apoptosis in the mechanism. In experiment 1, the rats were fed with 10%l-glutamine or 5% glycine diet injected with d-GalN with or without gadolinium chloride (GdCl₃)-pretreatment. The results indicated that these amino acids suppressed the d-GalN-induced elevation of serum transaminase activities, irrespective of GdCl₃-pretreatment. In experiment 2, rats were fed with 10% of l-glutamine, l-serine, l-alanine or l-glutamic acid diets injected with d-GalN. The results demonstrated that all these amino acids suppressed the d-GalN-induced elevation of serum transaminase activities, but that serum TNF-α concentrations and hepatic caspase-3 activities in the rats were not appreciably changed. In conclusion, the suppressive effects of amino acids on d-GalN-induced hepatitis were suggested not to be always mediated by the inhibition of Kupffer cells → TNF-α → apoptosis pathway.     

l-Arginine reduces thioflavin T fluorescence but not fibrillation of bovine serum albumin

This work examines the effects of l-arginine (l-Arg) on the aggregation and amyloid fibrillation of bovine serum albumin (BSA). We demonstrate that l-Arg dose-dependently reduces thioflavin T (ThT) fluorescence of BSA within the l-Arg concentration range used (0–1.4 M). However, as revealed by electron microscopy, size exclusion chromatography, and dynamic light scattering results, l-Arg does not prevent amyloid-like fibril formation by BSA. We conclude that l-Arg competes against ThT for binding sites on BSA amyloid-like fibrils, leading to biased results in ThT fluorescence measurements. Moreover, the use of ThT fluorescence assay to screen for potential inhibitors against amyloid fibrillation can give misleading results.     

Erythrocytes <Emphasis Type="SmallCaps">l</Emphasis>-Arginine y+ Transporter Inhibition by N-Ethylmaleimide in Ice-bath

Erythrocytes l-arginine uptake is conveyed by y+ and y+L membrane transport systems. Pre-incubation with N-ethylmaleimide for 10 min at 37°C inhibits the y+ system. The aim of this study was to determine the ideal pre-incubation temperature in evaluating y+ and y+L systems. Cells were pre-incubated with or without N-ethylmaleimide for 10 min at 4°C and 37°C. l-Arginine uptake was quantified by radioisotope and standard erythrocytes membrane flux methodology. Results demonstrate that erythrocytes l-arginine content is depleted by pre-incubation at 37°C for 10 min, thus changing the V _max measurement. The inhibitory effect of N-ethylmaleimide pre-incubation was temperature independent and already complete after 1 min of incubation. No significant difference in kinetic parameters was detected between cells pre-incubated at 37°C or 4°C, under zero-trans conditions. In conclusion, we suggest that measurement of erythrocytes l-arginine uptake by y+ and y+L systems could be carried out without N-ethylmaleimide pre-incubation at 37°C.     

<Emphasis Type="SmallCaps">l</Emphasis>-Proline is a sedative regulator of acute stress in the brain of neonatal chicks

The purpose of the present study was to clarify the central nervous system function of amino acids during acute stress. In Experiment 1, changes in free amino acid pattern were investigated in the brain of neonatal chicks exposed to either restraint with isolation-induced or fasting stress. l-Proline and l-arginine were decreased in the telencephalon and diencephalon under any stress. Since the central nervous system functions of l-arginine during the stress response has recently been reported, in Experiment 2, the effect of intracerebroventricular injection of l-proline (0.5, 1.0, 2.0 μmol) during isolation-induced stress was investigated. l-Proline induced sedative and hypnotic effects in a dose-dependent manner. It is suggested that l-proline may have an important role to attenuate the stress response in the central nervous system of chicks.