Different Concentrations Of L-arginine Research Articles

Evaluation of cellular viability in chitosan/L-arginine hydrogels.

There is a lack of studies evaluating the toxicity of nitric oxide (NO) precursors in chitosan/L-arginine hydrogels and their topical administration. However, clarifying the characteristics of these elements is essential for their possible use in non-surgical techniques of tooth movement acceleration. Such characteristics include interaction with different cell types, metabolism and drug safety. This in vitro study aimed to assess the cytotoxicity of chitosan hydrogels on human HeLa cells using different concentrations of L-arginine. The hydrogels were synthesized in a materials engineering laboratory, with a controlled environment, using 4 different L-arginine concentrations of 0%, 10%, 15%, and 20%. Once the hydrogels were prepared, their physical and chemical properties were characterized, and viability analysis was performed using 2 different methods, including a 48-h assay with Artemia salina nauplii and a 24-h cell culture with human HeLa cells followed by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation assay. Data analysis was performed using a Mann-Whitney U test to evaluate positive and negative controls in the cell culture, with a significance level of 0.01. A Wilcoxon paired test contrasted the 24-h compared to 48-h Artemia salina assays, with a Kruskal-Wallis and post hoc Dunn test used to compare groups using a significance level of 0.05. In the more viscous hydrogels, Artemia salina nauplii decreased drastically in 24 h, while the 15% and 20% hydrogels had no statistical differences from the negative control. The 10% and 20% hydrogels were statistically different from the negative control when comparing cell culture data. Our findings suggest that chitosan/L-arginine hydrogels could be used in humans without toxic effects. However, more trials and tests are needed to evaluate tooth movement rate during orthodontic treatment.

Comparison of the physical stability, microstructure and protein-lipid co-oxidation of O/W emulsions stabilized by l-arginine/l-lysine-modified soy protein hydrolysate

This work investigated the physical stability, microstructure, and oxidative stability of the emulsions prepared by soy protein hydrolysate (SPH) after modification with different concentrations of l-arginine and l-lysine. l-Arginine and l-lysine significantly increased the absolute zeta potential values, and decreased droplet sizes of the emulsions, thereby improving the physical stability of the emulsions. Meanwhile, l-arginine and l-lysine markedly decreased the apparent viscosity of the emulsions. The measurement of interfacial protein adsorption percentage showed that l-arginine (≤0.5 %) promoted the adsorption of SPH at the oil–water interface, whereas l-lysine (≤1%) reduced the adsorption of SPH at the oil–water interface. In addition, l-arginine and l-lysine (≤0.5 %) could retard lipid and protein oxidation. Correlation analysis indicated that the improvement in the physical stability of the emulsions by l-arginine and l-lysine also enhanced the oxidative stability of the emulsions. In summary, l-arginine and l-lysine could be effective modifiers for the protein-based emulsion systems.

Effects of Endothelin-1 and nitric oxide levels on myocardial ischemia-reperfusion injury.

To study the role of nitric oxide (NO) in myocardial ischemia-reperfusion injury (IRI) and Endothelin-1 (ET-1) in the process of reperfusion in an animal model. ET is a strong vasoconstrictor peptide, which is closely related to the physiological and pathological state of the cardiovascular system. ET not only directly stimulates and activates a variety of hormones and cytokines, but also is one of the mediators promoting myocardial remodeling, and participates in and promotes myocardial ischemia injury. Before myocardial ischemia, Krebs-Henseleit (KH) perfusion solution containing different concentrations of L-arginine (LA; substrate of NO) were given to 6 groups of rats, and ET was given at the early stage of reperfusion in 3 groups. During reperfusion, cardiac function indexes, myocardial enzyme release and NO content in coronary effluent, and the cardiac malondialdehyde (MDA) content was measured. The myocardial ultrastructure was observed by microscopy. Data of each group are expressed as mean ± standard deviation, and the baseline value of each group before ischemia was the recovery value during reperfusion. SPSS26.0 (IBM, Chicago, USA) was used for statistical processing. Before myocardial ischemia, infusion of KH solution containing a low concentration of LA (10 mmol/L) reduced myocardial IRI, whereas infusion of a KH solution containing high concentration of LA (100 mmol/L) before ischemia significantly aggravated myocardial IRI. The administration of KH solution containing LA and ET-1 (1,000 mmol/L) significantly reduced myocardial IRI. NO plays a dual role in myocardial ischemia-reperfusion, both beneficial and harmful. The combination of NO and ET-1 can reduce the toxic effect of NO.

Effect of adding different concentrations of L-arginine to Tris-yolk extender on the quality of sub-fertile ejaculates in buffalo.

To investigate the effect of supplementation of L-arginine (AR) on sub-fertile buffalo-bulls' ejaculates, 25 ejaculates of poor motility (40 to 55%) were collected by artificial vagina from 5 buffalo-bulls and extended with Tris-yolk extender (1:10) supplemented with different concentrations of AR (0, 3, 4, 5, and 6mM). Semen was cooled gradually to 4°C within 2h and incubated at 4°C for additional 2h. Incubated semen samples were evaluated by computer-assisted semen analysis. Results showed that addition of 5mM AR increased (P < 0.05) total sperm motility and rapid progressive motility percentages, while decreased (P < 0.05) non-motile sperm and static sperm percentages compared with AR-free (control) extender. Increasing the AR level to 6mM increased (P < 0.05) the percentages of sperm progressive motility and rapid and slow progressive motilities, while decreased (P < 0.05) the non-progressive sperm motility percentages compared with AR-free extender. Supplementation of 5mM AR improved (P < 0.05) sperm straight linear, curve linear, and average path velocities (36 ± 0.13, 20.6 ± 5.3, and 33.2 ± 8.5, respectively) in comparing with control and other AR treatments. Addition of AR (5 and 6mM) improved (P < 0.05) the percentages of vitality (89.8 ± 1.9 and 80.0 ± 3.4, respectively), normality (44.3 ± 3.6 and 44.8 ± 1.5, respectively), and functional sperm (20.4 ± 8.6 and 21.0 ± 0.61, respectively), and decreased abnormal neck and tail percentages compared with AR-free extender. All AR levels decreased (P < 0.05) the abnormal neck and tail percentages. Addition of all AR levels had no significant (P > 0.05) effect on the activity of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase in semen extender. Supplementation of Tris-yolk extender with L-arginine (5 or 6mM) can improve sperm motility, velocity, vitality, and functional sperm and can decrease tail and neck abnormalities of sub-fertile buffalo ejaculate after 4h incubation at cool temperature.

PSVIII-8 Effects of dietary L-arginine on growth performance, nutrient digestibility, and meat quality in finishing pigs

Abstract Arginine plays an important role in regulating arginine-nitric oxide synthase pathway, regulating lipid metabolism, and upregulating the mRNA levels of genes involved in fat synthesis in muscle in animals, and can therefore improve feed utilization for protein accretion. The objective of this study was to investigate the effects of supplementation of different concentrations of L-arginine on growth performance, nutrient digestibility, and meat quality in finishing pigs. A total of 120 crossbred [(Landrace × Yorkshire) × Duroc] pigs with an average initial body weight (BW) of 53.80 ± 1.86 kg were used in this 10-week feeding trial. The pigs were randomly allotted to 1 of 3 dietary treatments (5 pigs/pen and 8 replicates/treatment) in a randomized complete block design according to their sex (2 gilts and 3 barrows) and BW. Dietary treatments included: 1) CON, corn-soybean meal based basal diet (containing 13.81 MJ/kg metabolic energy and 0.95% lysine for entire experimental period); 2) LA0.5, CON + 0.5 g/kg L-arginine; 3) LA1.0, CON + 1.0 g/kg L-arginine. Individual body weight was measured initially and at the end of 5th and 10th week, feed consumption was recorded on pen basis during the experiment to determine growth performance. Meat samples were randomly taken from each pen (2 pigs per pen, 1 gilt and 1 barrow; 16 pigs per treatment) for determination of meat quality. All data were analysed using linear and quadratic contrast (SAS Institute Inc., Cary, NC, USA). The result showed that L-arginine did not affect pig growth performance and nutrient digestibility. However, dietary L-arginine supplementation linearly increased (P&amp;lt; 0.05) muscle marbling score, while linearly decreasing (P&amp;lt; 0.05) cooking loss and drip loss of pork muscle (Table 1). Results of present study demonstrated that 1.0 g/kg L-arginine would be beneficial in improving the meat quality in finishing pigs.

Pre-storage Application of L-arginine Alleviates Chilling Injury and Maintains Postharvest Quality of Cucumber (Cucumis sativus)

Chilling injury in cucumber is the major issue under low temperature storage, which substantially affects cosmetic quality and market value of fruits. Present study was aimed to assess the effect of L-arginine to alleviate surface pitting caused due to chilling injury and response of various quality attributes during cold storage (5 ± 1 °C; RH 90 ± 5%). Cucumber cv. ‘7003’ fruits were treated with different concentrations of L-arginine (0.0, 0.5, 1.0 and 1.5 mM) and stored for 16 days. Fruits were removed at 4 days storage interval followed by 1 day of conditioning (22 ± 2 °C) before quality analysis. Visual quality, fruit colour, decay, fruit weight loss, firmness, chilling injury (CI), electrolyte leakage, taste, texture, flavour, aroma, soluble solids content (SSC), titratable acidity (TA), sugar: acid ratio (SSC/TA ratio) and ascorbic acid content were measured for cucumber fruits. Overall, it was noted that L-arginine treated fruits showed lower fruit weight loss and electrolyte leakage, and maintained taste, texture, aroma, SSC, and sugar: acid ratio during storage. Fruits treated with 0.5 mM L-arginine had significantly reduced chilling injury and decay, maintained fruit colour, firmness and flavour, and displayed higher ascorbic acid content compared with control. Conclusively, pre-storage application of L-arginine (0.5 mM) can be employed as promising technique to alleviate postharvest chilling injury and maintain fruit quality of cucumber under cold storage.

L-Arginine metabolism alteration by L-Lysine intervention increased cell death in triple negative breast cancer cell

Abstract Background L-Arginine effectiveness cancer therapy is a matter of controversy. L-Arginine is a substrate for different metabolites influencing cancer cells. Arginase and nitric oxide synthase (NOS) are two important enzymes in the L-Arginine metabolic pathway. Nitric oxide (NO) is produced by NOS and the main products of arginase activity are polyamines. NO can decrease cancer cells viability dependent on its concentration but, polyamines shown to promote cancer cell growth/metastasis. Due to Arginase and NOS competition over L-Arginine binding, inhibition of arginase activity seems to increase NOS activity as well as NO production. Thus, the aim of the present study is to affect L-Arginine metabolic pathway through L-Lysine induced arginase inhibition in MDA-MB-231 and MDA-MB-468 Methods MDA-MB-231 and MDA-MB-468 were used as triple negative breast cancer cells with different arginase activity. Both cell lines were treated with different concentrations of L-Arginine and L-Lysine. Cell viability was assessed by MTT assay 24 and 48h after treatment. Arginase activity, ROS level and NO concentration was examined. Cell cycle was assessed using flowcytometry. Real-time PCR was performed to assess apoptotic and metabolic genes expression Results Our results indicated that cell viability and arginase activity were decreased in MDA-MB-468 with high arginase level more than MDA-MB-231 and studying the cell cycle also showed G2/M arrest in both cell lines following combination treatment with L-Lysine with L-Arginine. L-Lysine treatment resulted in increased apoptotic genes and decreased metabolic related genes expression in both cell lines Conclusion Altogether, our findings indicated that alternation in L-Arginine metabolic pathway using L-Lysine causes higher NO concentration which consequently increases cell death in triple negative breast cancer cells with different arginase level, which in turn can increase L-Arginine effect on cell lines with higher arginase activity

Fatal and non-fatal inflammatory injuries induced by different concentrations of L-arginine in Kunming rats

To establish animal models of fatal and non-fatal pancreatitis, we randomly divided 55 Kunming rats into three groups: Group A received three intraperitoneal injections of 8% L-arginine (L-arg); Group B received three intraperitoneal injections of 10% L-arg; and Group C (the control group) received three intraperitoneal injections of saline. After the third injection, biochemical indices and pathological changes in the pancreas and lungs were evaluated. In Group A, the rats experienced peak inflammatory edema at 48 h after the injections and exhibited the highest pathological score, but the biochemical indices showed no phase-related changes. In Group B, the rats exhibited significantly increased biochemical indices at 12 h after injection and experienced peak inflammatory edema at 24 h; the pathological score was also the highest, significantly different from the observations for Groups A and C ( P &lt; 0.05), and the mortality rate was 64% over 72 h. Thus, it was inferred that L-arg could be used to establish pancreatitis models and that different concentrations lead to different lesions.

Antioxidant Pre-Treatment Reduces the Toxic Effects of Oxalate on Renal Epithelial Cells in a Cell Culture Model of Urolithiasis.

Urolithiasis is characterized by the formation and retention of solid crystals within the urinary tract. Kidney stones are mostly composed of calcium oxalate, which predominantly generates free radicals that are toxic to renal tubular cells. The aim of the study is to explore possible effects of antioxidant pre-treatment on inhibition of oxidative stress. Three cell lines were used as in vitro model of urolithiasis: MDCK I, MDCK II and LLC-PK1. Oxidative stress was induced by exposure of cells to sodium oxalate in concentration of 8 mM. In order to prevent oxidative stress, cells were pre-treated with three different concentrations of l-arginine and vitamin E. Oxidative stress was evaluated by determining the expression of superoxide dismutase (SOD), osteopontin (OPN), and by the concentration of glutathione (GSH). In all three cell lines, pre-treatment of antioxidants increased cell survival. Positive correlation of SOD and OPN expression as well as GSH concentration was observed in all groups of cells. Our results indicate that an antioxidant pre-treatment with l-arginine and vitamin E is able to hamper oxalate-induced oxidative stress in kidney epithelial cells and as such could play a role in prevention of urolithiasis.

Effect of L-arginine treatment on motility, hyperactivity, acrosome reaction of ejaculated ram spermatozoa

The aim of this study was to evaluate the effect of in vitro treatment of ejaculated ram spermatozoa with different concentrations of L-arginine at various incubation times on motility, hyperactivity (HA) and acrosome reaction. Freshly ejaculated spermatozoa collected from three rams were pooled and subjected to the swim up technique in modified sperm Tyrode's albumin lactate pyruvate (S-TALP) medium supplemented with different concentrations of Larginine (0.01, 0.02, 0.03,0.04 and 0.05 mM) at 30, 60,90 and 120 min of incubation. Following sperm incubation, the following parameters were examined: motility, hyperactivity (HA) and acrosome reaction (AR). The results showed that irrespective of the concentration, incubation of ram spermatozoa with Larginine for 30min did not significantly affect the motility. However, increase the time of incubation for more than 30 min significantly decreased (P < 0.05) the motility of the spermatozoa as compared to the control. The lowest motility was recorded when spermatozoa were incubated with 0.05 mM L-arginine for 120 min. Treatment of ram spermatozoa with 0.05 mM Larginine resulted in a significant (P < 0.05) increase in HA% immediately after dilution compared to the control. A significant (P < 0.05) increase in total AR% was concomitant to the increase in the concentration of L-arginine with highest AR achieved at 0.04 mM and 90 min incubation. However, increasing the time of incubation to 120 min significantly decreased (P < 0.05) the percentage of spermatozoa with total AR compared to the other incubation times at 0.02, 0.04, and 0.05 mM L-arginine. In conclusion, under our experimental conditions treatment of ejaculated ram spermatozoa with 0.04 mM of L-arginine for 90 min was considered the best concentration of L-arginine to be used for in vitro induction of acrosome reaction.

52 Evaluation of marker proteins for quantitation of CFTR

Objectives: P. aeruginosa, a common pathogen in airways of patients with CF is sensitive to NOand nitrite-mediated killing. L-arginine is a substrate for nitric oxide (NO) synthase and arginase and both substitution of L-arginine and/or inhibition of arginase could have positive effects on Pseudomonas infection. We investigated the effect of L-arginine and of arginase inhibitor ABH on NOmetabolite formation in a novel CF sputum assay. Methods: Expectorated sputum was homogenized with the use of sputulysin and DPBS following standardized protocols before incubation with different concentrations of L-arginine or ABH. Nitrate and nitrite were measured using Griess reagent after 1 hour of incubation time at 37oC. Results: Total NO-metabolites (NOx) and nitrite concentrations were unaffected by incubation with buffer alone. L-arginine (10, 30, 100 and 300mmol) resulted in a concentration-dependent increase in both total NOx (1.7, 2.9, 3.9 and 3.9fold, p< 0.01, ANOVA) and nitrite (2.0, 3.4, 4.9 and 5.4-fold, p< 0.01). ABH (10, 30, and 100mmol) also resulted in a significant increase in NOx and nitrite (1.5fold, p< 0.01). The combination of ABH 1mmol with increasing concentrations of L-arginine (0, 0.33, 1, 3, and 10mmol) (n = 21) resulted in additive effects with significant increase in sputum nitrite observed for L-arginine of 3mmol and higher (p< 0.001) compared to ABH 1 mmol, respectively. Conclusions: Arginase inhibitor added to CF sputum alone or in combination with L-arginine significantly increases NO production. Studies to assess the effects of arginase inhibition on NO-mediated killing of bacteria in CF sputum are currently under way. 52 Evaluation of marker proteins for quantitation of CFTR

260 THE EFFECTS OF L-ARGININE ON CUMULUS CELL INTEGRITY AND MEIOTIC RESUMPTION DURING IN VITRO MATURATION OF BOVINE OOCYTES IN THE PRESENCE OF OVARIAN FOLLICLE HEMI-SECTIONS

Nuclear maturation of the oocytes, characterised by a resumption of meiosis, occurs at the end of the growing phase in preovulatory follicles, after the peak of gonadotropins. The mechanisms and substances involved, by which gonadotropins lead to the final nuclear maturation, are still unknown. The withdrawal of immature oocytes from the follicular environment is sufficient to trigger the spontaneous resumption of meiosis, hindering the study of these events in the in vitro model. However, the co-culture of immature oocytes with hemi-sections (HS) of follicular walls holds the meiosis arrest and is therefore an alternative system for evaluating the role of certain substances in the process of oocyte maturation. Nitric oxide is an important signalling molecule. There is evidence that NO is involved in the mechanisms that hold the meiotic arrest, and also in the events that lead to the resumption of nuclear maturation. Through the action of the NO synthase enzyme, l-arginine releases NO as a by-product. Thus, l-arginine may be considered a natural NO donor. This study tested the possible involvement of NO in the oocyte maturation process in in vitro conditions mimicking the in vivo environment. Different concentrations of l-arginine (2.5, 4, 5, 6, 10, and 50 mM) were added in the culture medium (200 µL of TCM-199/albumin). Groups of 20 cumulus–oocyte complexes were matured for 22 h at 38.5°C with 8 HS from the follicular wall. In addition, two controls (with and without HS) were processed. Membrane integrity of cumulus cells (CC) was evaluated, as well as the nuclear maturation of the oocytes at 22 h of culture, by double staining with Hoechst 33342 (10 µg mL–1) and propidium iodide (10 µg mL–1) and staining with 1% orcein, respectively. The results were assessed through ANOVA, and means were compared by t-test. There was an increase in the proportion of CC with intact membranes (P &lt; 0.05) in cumulus–oocyte complexes supplemented with at least 4 mM l-arginine [39.4 ± 9.8, 34.4 ± 18.1, 33.2 ± 0, 66.7 ± 24.1, 64.3 ± 15.9, 60.6 ± 12.8, 51.9 ± 19.3 (means ± SD) of CC with intact membrane for control with HS, without HS, and 2.5, 4, 5, 6, and 10 mM l-arginine, respectively], but a higher concentration (50 mM) of l-arginine had the opposite effect (20.3%). Similarly, concentrations of 4, 5, and 6 mM l-arginine increased the proportion of oocytes that reached intermediate stages (metaphase I, telophase I) of nuclear maturation when compared with the control with HS (P &lt; 0.05; 72.6 ± 12.5, 74.1 ± 9.5, 67.2 ± 19.3 v. 48.0 ± 11.7) and caused a trend for an increase in the proportion of oocytes at the metaphase-II stage [3.4 ± 4, 7.7 ± 10.9, 14.1 ± 14.4, 19.4 ± 13.4, 22.1 ± 28.2, 6.9 ± 6, 9 ± 0 (means ± SD) for the control with HS and 2.5, 4, 5, 6, 10, and 50 mM l-arginine respectively]. In conclusion, l-arginine improved the integrity of CC and may play a role in the nuclear oocyte maturation process in a dose-response manner. Further investigations are necessary to clarify the role of NO in these cellular processes. Supported by FAPERJ.

Effect of intramuscular injection of butaphosphan and vitamin B12 on the quality of fresh and cooled stallion semen

hyperactivation patterns of equine cryopreserved sperm. Three ejaculates were collected from each of three stallions (n1⁄49). Semen was packaged in 0.5-mL straws to a final concentration of 200 x 106 sperm/mL in Botu-Crio extender (Botupharma Animal Biotechnology) and frozen Frozen-thawed semen was then centrifuged in bovine in vitro fertilization medium supplemented with sodium bicarbonate and bovine serum albumin for the capacitation of equine sperm. The pellet was incubated in the same medium added with different concentrations of L-arginine (0; 2; 5; 10; 20 mM) for 0, 60, 120 and 300 minutes at 38 C under 5 % CO2. CASA was used for motility assessment. Spermwas considered hyperactivated when VCL was 180 mm/s and ALH was 12 mm. Data was analyzed using ANOVA and means in each time were compared with Tukey test, using SAS software. Total motility was not altered during neither incubation time nor treatment. There was a reduction in total motility when 10mM of L-arginine was added compared to 0, 2 and 5 mM (10 mM, time 0: 33.5 4.4; time 60: 29.3 5.4; time 120: 26.5 4.8; time 300: 14.9 3.0). A reduction in progressive motility was noted using concentration of 5 mM of L-arginine and higher (5 mM, time 0: 10.1 1.6; time 60: 10.9 2.3; time 120: 9.6 2.1; time 300: 5.9 1.2), however the concentration of 20 mM caused the greater decrease on this parameter (time 0: 5.7 0.8; time 60: 7.0 1.9; time 120: 7.5 1.9; time 300: 4.8 1.1). Increasing doses of L-arginine lead to a decrease in VAP, VSL and LIN (P < 0.05). VCL was not affected by the interaction of treatment and incubation time. ALH was not altered in the different incubation times or different treatments. STR, RAP and BCF results were lower for the cells treated with 20 mM of L-arginine compared to concentrations of 0, 5 e 10 mM in times 0, 60, 120 and 300 minutes of incubation. There was an interaction between treatments and incubation time (P < 0.05) in the percentage of hyperactivated cells. However, only at time 0 therewas difference among treatments, and hyperactivated cells percentage decreased in concentrations of L-arginineof 10mM. It canbe concluded that total motility and hyperactivated cells were reduced at 10mM L-arginine concentration and that increasing doses of L-arginine are prejudicial to motility sperm patterns in cryopreserved equine sperm.

Paradoxical effect of l-arginine: Acceleration of endothelial cell senescence

We have recently shown that inhibition of nitric oxide (NO) synthesis by asymmetrical dimethylarginine (ADMA) accelerated endothelial cell (EC) senescence which was prevented by coincubation with l-arginine; however the effect of long-term treatment of l-arginine alone on senescence of ECs have not been investigated. Human ECs were cultured in medium containing different concentrations of l-arginine until senescence. l-Arginine paradoxically accelerated senescence indicated by inhibiting telomerase activity. Moreover, l-arginine decreased NO metabolites, increased peroxynitrite, and 8-iso-prostaglandin F2α formation. In old cells, the mRNA expression of human amino acid transporter (hCAT)2B, the activity and protein expression of arginase II were upregulated indicated by enhanced urea, l-ornithine, and l-arginine consumption. Inhibition of arginase activity, or transfection with arginase II siRNA prevented l-arginine-accelerated senescence. The most possible explanation for the paradoxical acceleration of senescence by l-arginine so far may be the translational and posttranslational activation of arginase II.

C6. Effect of different concentrations of L-arginine on proliferation of human cervical carcinoma cell line (Hela)

C6. Effect of different concentrations of L-arginine on proliferation of human cervical carcinoma cell line (Hela)

Effects of L-arginine on the proliferation of T lymphocyte subpopulations.

Dietary supplementation of L-arginine as a mechanism to enhance cellular immune response (T lymphocytes), has slowly gained approval, and appears especially important during critical illness. Despite its clinical use, little is known as to the direct effects of L-arginine on the different T lymphocyte subpopulations. Lymphocytes were harvested from spleens of C57 B1/6 mice, and proliferation was induced with anti-CD3 in the presence of different concentrations of L-arginine ranging from 0 to 1000 micromol/L. Flow cytometry was used to evaluate the effect of L-arginine on T lymphocyte subpopulations. Interleukin-2 production was measured by ELISA and gene expression by RT-PCR. L-Arginine at or greater than 100 micromol/L significantly enhanced anti-CD3 stimulated T lymphocyte proliferation (p = .01). L-Arginine was essential for adequate T lymphocyte (CD3+) cellular maturation (p = .01). Proliferation of Helper T cells (CD4+) was not dependent on L-arginine. In contrast, Cytotoxic T cells (CD8+) showed a dose dependent proliferation in response to L-arginine (p = .01). Of the CD8+ cells, an increase in the CD45RA negative CD8 positive (memory) T cell subpopulation was observed with the addition of L-arginine. In addition, the number of cell surface CD8 receptors (CD8R) and CD3 receptors (CD3R) increased in the presence of L-arginine (p = .01, p = .04). Interleukin-2 receptor (IL-2R) expression was not up-regulated by L-arginine. L-Arginine modestly increased IL-2 production and had pronounced effects on its disappearance from the culture media (p < .0001). Interleukin-2 mRNA expression was not dependent on L-arginine. The requirements for L-arginine for the proliferation of CD3 stimulated T lymphocytes vary widely, and have to be taken into account when studying the mechanism of how L-arginine enhances cellular proliferation. L-Arginine may increase cellular proliferation by increasing specific receptor expression and the utilization of interleukin-2.

Arginine Activates Glycolysis of Goat Epididymal Spermatozoa: An NMR Study

The present study explores the mechanism underlying the action of l-arginine on the metabolic activity of spermatozoa. Goat epididymal spermatozoa were incubated with different concentrations of l-arginine to determine its effect on the utilization of glucose, fructose, and pyruvate. NMR techniques have been applied to elucidate the effect of l-arginine, l-lysine, and l-ornithine on the glycolysis of epididymal goat spermatozoa. Whereas 31P NMR has been used to estimate the change of pH in the presence of different concentrations of l-arginine, 13C NMR has been used to estimate the substrate consumption and lactate production. At optimal concentration of l-arginine, the forward metabolic rates have been found to increase by two to three times over control experiments. Arginine is not consumed in these reactions, but acts as an activator. Longitudinal relaxation time ( T 1) measurements indicate that the guanidino group of l-arginine plays an active role in binding to cells. The amino acid l-lysine is less effective, and l-ornithine is ineffective.

Possible involvement of nitric oxide in red nucleus stimulation-induced analgesia in the rat

There is considerable evidence that nitric oxide (NO) plays a role in synaptic transmission in both central and peripheral nervous systems. Recent studies have suggested the involvement of the l-arginine-NO pathway in nociceptive transmission/modulation. Electrical stimulation of the red nucleus in the rat evokes potent analgesia. Microinjection of different concentrations of l-arginine (1 nmol–1 μmol), but not of d-arginine, produced quick and long-lasting analgesia. Pretreatment with N-nitro- l-arginine methyl ester (1 μmol), a nitric oxide synthase inhibitor, significantly prevented l-arginine-induced analgesia. Further, pretreatment of animals with methylene blue, a known guanylate cyclase inhibitor, also attenuated the development of analgesia. Our results suggest that l-arginine caused production of NO, which in turn activated the red nucleus analgesic system.