Administration Of L-arginine Research Articles

Arginine nutrition and fetal brown adipose tissue development in nutrient-restricted sheep

Intrauterine growth restriction is a significant problem worldwide, resulting in increased rates of neonatal morbidity and mortality, as well as increased risks for metabolic and cardiovascular disease. The present study investigated the role of maternal undernutrition and L-arginine administration on fetal growth and development. Embryo transfer was utilized to generate genetically similar singleton pregnancies. On Day 35 of gestation, ewes were assigned to receive either 50 or 100% of their nutritional requirements. Ewes received i.v. injections of either saline or L-arginine three times daily from Day 100 to Day 125. Fetal growth was assessed at necropsy on Day 125. Maternal dietary manipulation altered circulating concentrations of leptin, progesterone, and amino acids in maternal plasma. Fetal weight was reduced in nutrient-restricted ewes on Day 125 compared with 100% fed ewes. Compared with saline-treated underfed ewes, maternal L-arginine administration did not affect fetal weight but increased weight of the fetal pancreas by 32% and fetal peri-renal brown adipose tissue mass by 48%. These results indicate that L-arginine administration enhanced fetal pancreatic and brown adipose tissue development. The postnatal effects of increased pancreatic and brown adipose tissue growth warrant further study.

L-arginine suppresses ischemia/reperfusion induced up-regulation of endothelin-1 production in a rat model of acute myocardial injury

To examine the level of endothelin-1 (ET-1) in serum and its expression in myocardium tissue during the development of acute myocardial ischemia/reperfusion (I/R) injury in rat and the effects of L-arginine (L-Arg) administration on these indexes. One hundred and ten Wistar rats were randomly divided into nine groups to receive: (1) sham surgery, (2)ischemia (I, by ligation of anterior descending coronary artery for 30 minutes), (3) I+reperfusion (R, by the removal of the ligature) for 0.5 hour, (4) I+R for 1 hour, (5) I+R for 2 hours; group (6) ~ (9) also received I/R treatment as in group 2 ~ 5 respectively but with L-Arg pretreatment. Blood and myocardium tissue samples were collected by the end of the experiment for the analysis of: serum level of creatine kinase (CK), lactate dehydrogenase [LDH, by enzyme linked immunosorbent assay (ELISA)], ET-1 (radioimmunoassay), and the tissue content of ET-1 mRNA/peptide [by reverse-transcription polymerase chain-reaction (RT-PCR) and Western blotting]. In comparison with the sham treated control animals, the serum levels of CK, LDH, and ET-1 were all significantly higher in the groups treated with I/R (particularly those exposed to reperfusion). The myocardial tissue content of ET-1 mRNA/peptide were also significantly increased in I/R treated groups (particularly the I+R 2 hours group) as compared to control (ET-1 mRNA: 0.775 ± 0.029 vs. 0.310 ± 0.076; ET-1 peptide: 0.773 ± 0.055 vs. 0.340 ± 0.099, both P < 0.05). The i.v. administration of L-Arg significantly suppressed the up-regulation of tissue content of ET-1 mRNA /peptide in I/R treated animals (ET-1 mRNA: 0.340 ± 0.049 vs. 0.775 ± 0.029; ET-1 peptide: 0.390 ± 0.094 vs. 0.773 ± 0.055, both P < 0.05). L-Arg may be tested during certain stage of I/R injury as a therapeutic intervention for the suppression of ET-1 up-regulation.

L-Arginine stimulates the mTOR signaling pathway and protein synthesis in porcine trophectoderm cells

Impairment of placental growth is a major factor contributing to intrauterine growth retardation (IUGR) in both human pregnancy and animal production. Results of recent studies indicate that administration of l-arginine (Arg) to gestating pigs or sheep with IUGR fetuses can enhance fetal growth. However, the underlying mechanisms are largely unknown. The present study tested the hypothesis that Arg stimulates the mammalian target of rapamycin (mTOR) signaling pathway and protein synthesis in porcine conceptus trophectoderm (pTr2) cells. The cells were cultured for 4 days in Arg-free Dulbecco's modified Eagle's Ham medium containing 10, 50, 100, 200, 350 or 500 μM Arg. Cell numbers, protein synthesis and degradation, as well as total and phosphorylated levels of mTOR, ribosomal protein S6 kinase 1 (p70S6K) and eukaryotic initiation factor 4E-binding protein-1 (4EBP1), were determined. The pTr2 cells exhibited time (0–6 days)- and Arg concentration (10–350 μM)-dependent increases in proliferation. Addition of 100 and 350 μM Arg to culture medium dose-dependently increased (a) protein synthesis and decreased protein degradation and (b) the abundance of total and phosphorylated mTOR, p70S6K and 4EBP1 proteins. Effects of 350 μM Arg on intracellular protein turnover were only modestly affected when nitric oxide synthesis was inhibited. Collectively, these results indicate a novel and important role for Arg in promoting growth of porcine placental cells largely via a nitric-oxide-independent pathway. Additionally, these findings help to explain beneficial effects of Arg supplementation on improving survival and growth of embryos/fetuses in mammals.

Sunitinib-Induced Systemic Vasoconstriction in Swine Is Endothelin Mediated and Does Not Involve Nitric Oxide or Oxidative Stress

Angiogenesis inhibition with agents targeting tyrosine kinases of vascular endothelial growth factor receptors is an established anticancer treatment, but is, unfortunately, frequently accompanied by systemic hypertension and cardiac toxicity. Whether vascular endothelial growth factor receptor antagonism also has adverse effects on the pulmonary and coronary circulations is presently unknown. In chronically instrumented awake swine, the effects of the vascular endothelial growth factor receptor antagonist sunitinib on the systemic, pulmonary, and coronary circulation were studied. One week after sunitinib (50 mg PO daily), mean aortic blood pressure (MABP) had increased from 83±5 mm Hg at baseline to 97±6 mm Hg (P<0.05) because of a 57±20% increase in systemic vascular resistance as cardiac output decreased. In contrast, sunitinib had no discernible effects on pulmonary and coronary hemodynamics or cardiac function. We subsequently investigated the mechanisms underlying the sunitinib-induced systemic hypertension. Intravenous administration of NO synthase inhibitor N(G)-nitro-l-arginine increased MABP by 24±1 mm Hg under baseline conditions, whereas it increased MABP even further after sunitinib administration (32±3 mm Hg; P<0.05). Reactive oxygen species scavenging with a mixture of antioxidants lowered MABP by 13±2 mm Hg before but only by 5±2 mm Hg (P<0.05) after sunitinib administration. However, intravenous administration of the dual endothelin A/endothelin B receptor blocker tezosentan, which did not lower MABP at baseline, completely reversed MABP to presunitinib values. These findings indicate that sunitinib produces vasoconstriction selectively in the systemic vascular bed, without affecting pulmonary or coronary circulations. The sunitinib-mediated systemic hypertension is principally attributed to an increased vasoconstrictor influence of endothelin, with no apparent contributions of a loss of NO bioavailability or increased oxidative stress.

P-selectin mediates neutrophil rolling and recruitment in acute pancreatitis

The adhesive mechanisms regulating leucocyte-endothelium interactions in the pancreas remain elusive, but selectins may play a role. This study examined the molecular mechanisms mediating leucocyte rolling along the endothelium in the pancreas and the therapeutic potential of targeting the rolling adhesive interaction in acute pancreatitis (AP). Pancreatitis was induced by retrograde infusion of 5 per cent sodium taurocholate into the pancreatic duct, repeated intraperitoneal administration of caerulein (50 µg/kg) or intraperitoneal administration of L-arginine (4 g/kg) in C57BL/6 mice. A control and a monoclonal antibody against P-selectin were administered before and after induction of AP. Serum and tissue were sampled to assess the severity of pancreatitis, and intravital microscopy was used to study leucocyte rolling. Taurocholate infusion into the pancreatic duct increased the serum level of trypsinogen, trypsinogen activation, pancreatic neutrophil infiltration, macrophage inflammatory protein (MIP) 2 formation and tissue damage. Immunoneutralization of P-selectin decreased the taurocholate-induced increase in serum trypsinogen (median (range) 17·35 (12·20-30·00) versus 1·55 (0·60-15·70) µg/l; P = 0·017), neutrophil accumulation (4·00 (0·75-4·00) versus 0·63 (0-3·25); P = 0·002) and tissue damage, but had no effect on MIP-2 production (14·08 (1·68-33·38) versus 3·70 (0·55-51·80) pg/mg; P = 0·195) or serum trypsinogen activating peptide level (1·10 (0·60-1·60) versus 0·45 (0-1·80) µg/l; P = 0·069). Intravital fluorescence microscopy revealed that anti-P-selectin antibody inhibited leucocyte rolling completely in postcapillary venules of the inflamed pancreas. Inhibition of P-selectin protected against pancreatic tissue injury in experimental pancreatitis. Targeting P-selectin may be an effective strategy to ameliorate inflammation in AP.

Nitric oxide in the nucleus accumbens is involved in retrieval of inhibitory avoidance memory by nicotine

In the present study, the possible effect of nitric oxide agents injected into the nucleus accumbens (NAc) in the presence or absence of nicotine on morphine state-dependent memory in adult male Wistar rats was investigated. As a model of memory, a step-through type inhibitory avoidance task was used. Post-training injection of morphine (4 and 6mg/kg) dose dependently induced the impairment of memory retention. Administration of morphine (4 and 6mg/kg) before retention induced state-dependent retrieval of the memory acquired under post-training morphine (6mg/kg) influence. Injection of nicotine before retention (0.25 and 0.5mg/kg) alone and nicotine (0.1, 0.25 and 0.5mg/kg) plus an ineffective dose of morphine (2mg/kg) reversed the post-training morphine-induced memory impairment. The amnesia elicited by morphine (6mg/kg) was also prevented by pre-retention intra-NAc administration of a nitric oxide synthase (NOS) inhibitor, l-NAME (0.24μg/rat, intra-NAc). Interestingly, an ineffective dose of nicotine (0.1mg/kg) in combination with low doses of l-NAME (0.06 and 0.12μg/rat, intra-NAc) synergistically improved memory performance impaired by morphine given after training. It is important to note that intra-NAc administration of l-NAME before retention impaired memory retrieval by itself. In contrast, pre-retention administration of l-arginine, a nitric oxide (NO) precursor (0.25 and 0.5μg/rat, intra-NAc), which had no effect alone, prevented the nicotine reversal of morphine effect on memory. The results suggest a possible role for nitric oxide of nucleus accumbens in the improving effect of nicotine on the morphine-induced amnesia and morphine state-dependent memory.

Antioxidant preserving effects of l-arginine at reducing the hemodynamic toxicity of gentamicin-induced rat nephrotoxicity: pathological and biochemical findings

Nephrotoxicity results from an abrupt decline in glomerular functions of the kidney and is regarded as a major cause of concern for limiting therapeutic uses of gentamicin in hospital settings. Recent evidences suggest that both endothelial nitric oxide synthesis (eNOS) and inducible NOS (iNOS)-derived nitric oxide (NO) vasodilators reduce renal toxicity, restoring normal glomerular functions and hemodynamic stability, but this has not been adequately investigated in gentamicin nephrotoxicity. To determine the isoform of NOS that plays a predominant role in the control of glomerular vasodilation under the oxidative stress of nephrotoxicity, we conducted a controlled, randomized study in five equal groups of ten Sprague–Dawley rats. All animals were given a corresponding dose of either normal saline, only l-arginine, only gentamicin, or a combination thereof with and without N-3-aminomethyl benzylacetamidine (a selective iNOS inhibitor, 1400W) for 9 days. After 6 days, gentamicin-treated rats developed nephrotoxic alterations evident by a significant fall in renal blood flow and glomerular filtration rate, increased urinary excretion of gamma glutamyl transpeptidase and serum concentration of inflammatory interleukins (IL-6 and IL-8) as well as a decrease in the tissue antioxidant activity of superoxide dismutase. Changes in these biochemical variables were completely inhibited by supplemented l-arginine up to 9 days. However, a combination of 1400W partially removed protective effects of l-arginine on the glomerular hemodynamics of the kidney. Our results suggest that at irradiation of eNOS developed by increased oxidative process, administration of l-arginine increases iNOS-derived NO production and glomeruli infiltration on its direct antioxidant effects counteracting the undesirable effects of peroxynitrite formation on the kidney.

Reduction in Inflammatory Markers Expression in Serum is Related to Improvement in Renal Functions in Intrauterine Undernourished Rats

Background and aims: Maternal undernutrition can induce a range of fetal adaptations, which can lead to permanent alterations in adulthood. Interleukin (IL)-18 play an integral role in tubular injury and the development of renal dysfunction during a variety of inflammatory processes. In this work, we have investigated the impact of intrauterine undernutrition on the inflammatory markers, and the correlation of these markers with the renal dysfunction; the effect of L-arginine (L-arg)administration on those parameters also was investigated.Methods: Female Wistar rats were randomly divided into 2 groups: nourished(NR-ad libitum diet) and undernourished (UR-50% food restriction). After birth, each litter was left with the mother for 28 days. Some of the offspring received a 2% L-Arg solution in drinking water (groups NR+L-Arg and UR+L-Arg). Proteinuria and glomerular filtration rate (GFR) were determined. IL-18 and cytokine induced neutrophil chemoattractant-2 (CINC-2) were evaluated by Bioplex, in serum.Results: In UR, the proteinuria (63%), IL-18 (121%) and CINC-2 (61%) were increased, when compared to NR, and the L-arg treatment abolished these effects; the GFR was decreased in UR (43%), and the L-arg treatment prevented this reduction.Conclusions: In UR, the inflammatory markers, such as IL-18, are present in an early stage after birth, probably contributing for the development of renal injury in this model. The lower expression of these markers seems to be directly related to improvement of renal function. Our results suggest that these inflammatory markers can be attenuated by L-arginine.Supported by FAPESP, CNPq, and INCT Complex Fluids

The Influence of Maternal Diabetes on the Expression of Inflammatory Markers in the Offspring

Background and aims: Previous studies from our group have shown that maternal diabetes is an important cause of glomerular hypertrophy in the offpring (DO) and that hypertension linked to an impaiment in the vascular endothelium-dependent relaxation is early detected. The present study was designed to evaluate the expression of cytokines/chemokines in plasma and renal tissue from DO and the possible effect of L-arginine administration on those parameters.Methods: Diabetes mellitus was induced in Wistar female rats with a single dose of streptozotocyn, 50mg/kg, IP. Diabetic dams were caged overnight with a male. After birth, each litter was left with the mother for 28 days. Some of the offspring received a 2% L-Arg solution in drinking water (groups DA and CA, controls+ L-arg). Tumor necrosis factor-alpha (TNF-α), interleukin (IL) -6 and IL-1b were measured by real time PCR in the kidney from 2 and 6 month-old rats.Results: Serum expression of TNF-α, interleukin (IL)-1b, IL-2, IL-17, interferon (IFN)-g, macrophage inflammatory protein (MIP)-1and leptin enhanced in DO group and L-arg prevented this increase. TNF-α, interleukin (IL) -6 and IL-1b (measured by real time PCR) in the kidney from DO, 6 month-old, were also increased but returned to control values in DA.Conclusions: Renal and serum inflammatory pathways seem to be early activated in DO, contributing or being the triggering factor for the development of hypertension and renal injury in this model. Our results suggest that these inflammatory pathways can be attenuated by L-arginine.Supported by FAPESP and CNPq

Strategies for optimizing the serum persistence of engineered human arginase I for cancer therapy

Systemic l-arginine depletion following intravenous administration of l-arginine hydrolyzing enzymes has been shown to selectively impact tumors displaying urea cycle defects including a large fraction of hepatocellular carcinomas, metastatic melanomas and small cell lung carcinomas. However, the human arginases display poor serum stability (t1/2=4.8h) whereas a bacterial arginine deiminase evaluated in phase II clinical trials was reported to be immunogenic, eliciting strong neutralizing antibody responses. Recently, we showed that substitution of the Mn2+ metal center in human Arginase I with Co2+ (Co-hArgI) results in an enzyme that displays 10-fold higher catalytic efficiency for L-Arg hydrolysis, 12–15 fold reduction in the IC50 towards a variety of malignant cell lines and, importantly a t1/2=22h in serum. To investigate the utility of Co-hArgI for L-Arg depletion therapy in cancer we systematically investigated three strategies for enhancing the persistence of the enzyme in circulation: (i) site specific conjugation of Co-hArgI engineered with an accessible N-terminal Cys residue to 20kDa PEG-maleimide (Co-hArgI-CPEG-20K); (ii) engineering of the homotrimeric Co-hArgI into a linked, monomeric 110kDa polypeptide (Co-hArgI x3) and (iii) lysyl conjugation of 5kDa PEG-N-hydroxysuccinimide (NHS) ester (Co-hArgI-KPEG-5K). Surprisingly, even though all three formulations resulted in proteins with a predicted hydrodynamic radius larger than the cut-off for renal filtration, only Co-hArgI amine conjugated to 5kDa PEG remained in circulation for sufficiently long durations. Using Co-hArgI-KPEG-5K labeled with an end-terminal fluorescein for easy detection, we demonstrated that following intraperitoneal administration at 6mg/kg weight, a well tolerated dose, the circulation t1/2 of the protein in Balb/c mice is 63±10h. Very low levels of serum L-Arg (<5μM) could be sustained for over 75h after injection, representing a 9-fold increase in pharmacodynamic efficacy relative to similarly prepared Mn2+-containing hArgI conjugated to 5kDa PEG-NHS ester (Mn-hArgI-KPEG-5K). The favorable pharmacokinetic and pharmacodynamic properties of Co-hArgI-KPEG-5K reported here, coupled with its human origin which should reduce the likelihood of adverse immune responses, make it a promising candidate for cancer therapy.

The influence of short-term l-arginine supplementation on rats’ muscular and hepatic cells in ischemia–reperfusion syndrome

Due to the complex mechanisms of L-arginine activity, it is difficult to determine the clinical significance of supplementation with this amino acid. The objective of this study was to determine the influence of short-term supplementation with L-arginine in stress conditions, induced by ischemia-reperfusion syndrome, by assessing the damage to muscular and hepatic cells on the basis of creatine kinase (CK), alanine aminotransferase (ALAT) and aspartic aminotransferase (AspAT) activity in blood and the level of oxygen free radicals in analyzed tissues of rats. We observed that induced ischemia of hind limb caused an increase in CK, ALAT and AspAT activity and an increase in the level of free radicals in liver, but not in skeletal muscle. Supplementation with L-arginine led to a reduction in serum activity of CK and AspAT and reduction of the level of free radicals in analysed tissues. Simultaneous supplementation with L -arginine AND L-NAME resulted in a reversal of changes induced by L-arginine supplementation in the case of AspAT and free radicals in skeletal muscle. The results indicate that under conditions of ischemia-reperfusion, short-term administration of L-arginine has a protective effect on skeletal muscle manifesting itself by reduction of CK in the serum and reduction of free radicals level in THIS tissue.

S124 EFFECTS OF NITRIC OXIDE ON THE PREFRONTAL CORTEX IN STRESSED RATS

BACKGROUND: Nitric oxide (NO) exhibits both protective and detrimental effects in the central nervous system. OBJECTIVE: To investigate the effect of NO on the prefrontal cortex in neonatal stressed rats. DESIGN, TIME AND SETTING: A randomized, controlled, animal study was performed at the Anatomical Department of Iran University of Medical Sciences from May 2007 to August 2008. MATERIALS: Forty-eight male, Wistar rats were obtained from Pasteur’s Institute, Tehran, Iran. METHODS: Rat stress models were established by immobilization and randomly received intraperitoneal injection of 2 mL physiological saline, L-arginine (200 mg/kg) as a NO precursor, N(G)-nitro-L-arginine methyl ester (20 mg/kg), or subcutaneous injection of 7-nitroindazole (25 mg/kg) as a NO synthase inhibitor. MAIN OUTCOME MEASURES: After the rats were treated for 4 weeks, the frontal cortex was harvested for histological observation and NO detection. RESULTS: Subcutaneous administration of N(G)-nitro-L-arginine methyl ester or 7-nitroindazole resulted in significantly lower prefrontal cortex thickness and NO production compared with subcutaneous administration of L-arginine (P < 0.05). Prefrontal cortex thickness significantly increased in rats following L-arginine treatment, compared with physiological saline intervention (P < 0.05). CONCLUSION: NO exhibited protective effects on the prefrontal cortex of stressed rats.

Contribution of nitric oxide synthase (NOS) in blood–brain barrier disruption during acute focal cerebral ischemia in normal rat

Endogenous level of nitric oxide (NO) is increased in the brain following the stroke, and deactivation of NO synthase has been shown to attenuate its destructive actions in animal stroke models using middle cerebral artery occlusion (MCAO) procedures. However, little is known about the effects of NO in cerebral vascular integrity and edema during acute cerebral ischemia. Here we investigated whether NO plays any role in the progression of blood–brain barrier (BBB) disruption and edema formation in ischemia/reperfusion injury. Intraperitoneal administration of NO substrate l-arginine (300mg/kg), or NOS inhibitor (l-NAME, 1mg/kg), was done in normal rats at 20min before a 60-min MCAO. Mean arterial blood pressures (MAP) and regional cerebral blood flow (rCBF) were continuously recorded during experiment. Neurological deficit score (NDS) was evaluated 12h after termination of MCAO followed with evaluations of cerebral infarction volume (CIV), edema formation and cerebral vascular permeability (CVP), as determined by the Evans blue dye extravasations (EBE) technique. No significant changes were observed in the values of MAP and rCBF with l-arginine or l-NAME during ischemia or reperfusion periods. There was a 75–85% reduction in rCBF in during MCAO which returned back to its pre-occlusion level during reperfusion. Acute cerebral ischemia with or without l-arginine augmented NDS (4.00±0.44 and 3.00±0.30), in conjunction with increased CIV (518±57mm3 and 461±65mm3), provoked edema (3.09±0.45% and 3.30±0.49%), and elevated EBE (8.28±2.04μg/g and 5.09±1.41μg/g). Inhibition of NO production by l-NAME significantly improved NDS (1.50±0.22), diminished CIV (248±56mm3), edema (1.18±0.58%) and EBE (1.37±0.12μg/g). This study reconfirms the cerebroprotective properties of reduced tissue NO during acute ischemic stroke, and it also validates the deleterious actions of increased NOS activity on the disruption of cerebral microvascular integrity and edema formation of ischemia/reperfusion injuries in normal rat, without changing arterial blood pressure or blood flows to ischemic regions.

Modulation of nitrergic pathway by sesamol prevents cognitive deficits and associated biochemical alterations in intracerebroventricular streptozotocin-administered rats

Alzheimer's disease is a neurodegenerative disorder characterized by progressive cognitive decline and widespread loss of neurons and their synapses in the cerebral cortex and hippocampus. Increasing evidence indicates that factors such as oxidative-nitrergic stress, glutathione depletion, impaired protein metabolism and cholinergic deficit can interact in a vicious cycle, which is central to Alzheimer's disease pathogenesis. Intracerebroventricular (i.c.v.) streptozotocin induced-cognitive impairment has been widely used as an experimental paradigm to study Alzheimer's disease. In the present study, i.c.v. streptozotocin produced significant cognitive deficits as measured in Morris water maze and elevated plus maze task coupled with increased serum TNF-α levels and marked rise in brain acetylcholinesterase and oxidative-nitrergic stress in female Wistar rats. Sesamol (5-hydroxy-1,3-benzodioxole or 3,4-methylenedioxyphenol), a potent anti-oxidant and anti-inflammatory molecule markedly improved cognitive impairment, reduced acetylcholinesterase activity, TNF-α levels and attenuated oxidative-nitrergic stress in brain of i.c.v.-streptozotocin treated rats. Administration of L-arginine (125 mg/kg i.p), a nitric oxide donor, alone to i.c.v.-streptozotocin treated rats accentuated behavioral and biochemical deficits and also abolished the protective effect of sesamol (8 mg/kg). L-NAME (10 mg/kgi.p.), a non-specific NOS inhibitor significantly restored all the behavioral and biochemical indices in i.c.v.-streptozotocin rats. Moreover, combination of L-NAME with sub-effective dose of sesamol (4 mg/kg) potentiated its protective effect. Our findings demonstrate the effectiveness of sesamol in preventing intracerebroventricular streptozotocin-induced cognitive deficits by modulating nitrergic signaling and oxido-inflammatory cascade.

The effect of L‐arginine or L‐citrulline supplementation on biochemical parameters and the vascular aortic wall in high‐fat and high‐cholesterol‐fed rats

The aim of the present study is to investigate the potential role of L-arginine or L-citrulline in rats fed high-fat and high-cholesterol (HFC) diet. HFC feeding increased significantly serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, urea and all lipid profiles and decreased significantly serum high-density lipoprotein-cholesterol (HDL-c) and non significantly serum nitric oxide levels. L-arginine or L-citrulline administration reversed the increase in serum AST and ALT activities, urea and all lipid profiles. These effects were associated with a concomitant increase in HDL-c and nitric oxide levels. In general, rats fed HFC diet and orally treated with L-arginine or L-citrulline had higher relative percentage of 18:0, 20:0 and 22:6 and lower 16:0 fatty acids than rats fed HFC diet. Light and transmission electron microscopic findings of the thoracic aorta confirmed the biochemical results and demonstrated structural changes in the endothelial cells of the intimal layer, medial smooth muscle cells as well as in the adventitial layer in HFC fed-animals. However, these findings indicate little structural alterations in animals supplemented with L-arginine or L-citrulline along with HFC feeding. In the present study, L-arginine or L-citrulline was effective hypocholesterolemic and hypolipidemic agents in rats.

Role of combination of l‐arginine and α‐tocopherol in renal transplantation ischaemia/reperfusion injury: a randomized controlled experimental study in a rat model

What's known on the subject? and What does the study add? Renal ischaemia/reperfusion (I/R) injury is an inevitable consequence of kidney transplantation. It contributes to delayed graft function (DGF), acute renal failure and graft rejection. The present study investigates for the first time the impact of a combination of L-arginine and alpha tocopherol on the renal ischemia/reperfusion injury in a rodent model of kidney transplantation. We found that concomitant administration of L-arginine and α-tocopherol has a more protective effect and synergistic antioxidant effect on ischaemia/reperfusion injury in transplanted rat kidneys. To investigate the role of L-arginine and α-tocopherol in ischaemia/reperfusion injury in a kidney transplanted rat model. In total, 40 male Sprague-Dawley rats subjected to renal transplantation received FK506 (tacrolimus) to overcome early acute rejection episodes. Animals were divided randomly into four groups (ten rats each). Group I were treated with FK506 (2 mg/kg/bw/day) and served as the control group. Group II were treated with L-arginine 300 mg/kg/bw. Group III were treated with α-tocopherol 30 mg/kg/bw. Group IV were treated with L-arginine and α-tocopherol. Urine and blood samples were taken at 0 (before operation), 2, 7 and 14 days post-transplantation for estimation of urine sodium, creatinine, fractional excretion of sodium, serum creatinine, sodium and blood urea nitrogen. Histological examination and measurement of malondialdehyde in kidney tissues were also performed. Serum creatinine and blood urea nitrogen significantly decreased in L-arginine and α-tocopherol, as well as combination groups, compared to the control group. Malondialdehyde was significantly decreased in the combination group compared to L-arginine and α-tocopherol alone. Histological examination of the control group showed that acute tubular necrosis was markedly decreased in transplanted kidneys treated with a combination of both L-arginine and α-tocopherol. Concomitant administration of l-arginine and α-tocopherol has a more protective effect and synergistic antioxidant effect on ischaemia/reperfusion injury in transplanted rat kidneys.

The acute effects of a low and high dose of oral l-arginine supplementation in young active males at rest

L-arginine (2-amino-5-guanidinovaleric acid) is a conditionally essential amino acid. Intravenous (IV) administration of l-arginine invokes a large metabolic (nitrate/nitrite (NO(x))) and hormonal (growth hormone (GH), insulin-like growth factor 1 (IGF-1), and insulin) response; however, research examining oral l-arginine supplementation is conflicting, potentially owing to dose. The purpose of this study was examine a low and high dose of oral l-arginine on blood l-arginine, NO(x), GH, IGF-1, and insulin response. Fourteen physically active males (age: 25 ± 5 years; weight: 78.0 ± 8.5 kg; height: 179.4 ± 4.7 cm) volunteered to be in a randomized, double-blind, repeated-measures study. Following an overnight fast, an IV catheter was placed in a forearm vein and a resting blood sample was drawn at ∼0800 hours. Each subject was then provided 1 of 3 treatment conditions (placebo, low (0.075 g·kg(-1) of body mass), or high (0.15 g·kg(-1) of body mass of l-arginine)). Blood samples were drawn at 30, 60, 90, 120, and 180 min after consumption. l-arginine plasma concentrations significantly increased (p < 0.001) to a similar level at any time point in both the low- and high-dose conditions; there was no change over time in the placebo condition. There was no significant difference between conditions for NO(x), GH, IGF-1, or insulin. Based on these findings, a low dose of l-arginine was just as effective at increasing plasma l-arginine concentrations as a high dose; however, neither dose was able to promote a significant increase in NO(x), GH, IGF-1, or insulin at rest.

Protective effect of L-arginine administration on proteins of unloaded m. soleus

Cytoskeletal and contractile proteins degenerate during functional unloading of muscle. The ratio of myosin heavy chain (MHC) expression changes simultaneously. We have supposed that NO can be a signal molecule related to the regulation of protein metabolism upon muscle unloading. To test this hypothesis, Wistar rats underwent functional unloading for 14 days without and with peroral administration of L-arginine (500mg/kg) as NO precursor. Significant decreases in m. soleus mass, NO, nNOS, dystrophin, Hsp90, p-S6K, and type I MHC mRNA contents were found in the group of animals with unloading without preparation compared to those in control and in the group with unloading and administration of L-arginine; at the same time, increased contents of atrogin-1/MAFbx and MuRF-1 (p < 0.05) were found. No difference in the IGF-1 mRNA content between all three groups was found. Atrophy was significantly less pronounced in the group with unloading and L-arginine administration compared to that without the amino acid, and no destruction of cytoskeletal proteins was observed. We conclude that administration of L-arginine upon functional unloading decreases the extent of m. soleus atrophy, prevents the decrease in it of type I MHC mRNA, and blocks destructive changes in some cytoskeletal proteins. Such effect can be due to the absence of increase in this group of the content of some ubiquitin ligases and decreased intensity of the p70S6 kinase synthesis marker.

Differential effects of physical exercise and l-arginine on cortical spreading depression in developing rats

ObjectiveWe investigated the effect of early-in-life administration of l-arginine, combined with physical exercise, on cortical spreading depression (CSD) in young and adult rats.Methodsl-arginine (300 mg/kg/day, n = 40) or distilled water (vehicle, n = 40) was given to the rats during postnatal days 7–35 by gavage. Physical exercise (treadmill) was carried out during postnatal days 15–35 in half of the animals in each gavage condition described above. The other half (non-exercised) was used for comparison. When the animals reached 35–45 days (young groups) or 90–120 days of age (adult) CSD was recorded on two cortical points during 4 hours and CSD propagation velocity was calculated.Resultsl-arginine-treated + exercised rats had increased body weight, but not brain weight, in adult age compared to l-arginine + non-exercised ones (P < 0.05). In both young and adult animals, l-arginine increased, whereas exercise decreased the CSD propagation velocity. Analysis of variance revealed a significant interaction between gavage treatment and age (P < 0.001), and also between gavage treatment and exercise (P = 0.004), but not between age and exercise. An additional control group of young rats, treated with 300 mg/kg of l-histidine, presented CSD velocities comparable to the corresponding water-treated controls, suggesting that the CSD acceleration seen in the l-arginine group was an l-arginine-specific effect, rather than an effect due to a non-specific amino acid imbalance.Discussionl-arginine and exercise affect CSD differentially (l-arginine accelerated, while exercise decelerated CSD), and both effects did interact. Probably, they depend on developmental plasticity changes associated with the treatments.

Early Administration of l-Arginine in Experimental Acute Spinal Cord Injury Impairs Long-Term Motor Function Recovery

Recently, we reported that L-arginine, a nitric oxide precursor, reverses altered drug disposition induced by acute spinal cord injury (SCI) by increasing hepatic blood flow, without affecting mean arterial pressure and heart rate, whereas others have shown that it produces neuroprotection in several models of acute neurologic damage. Its use as a therapeutic agent for microcirculatory alterations associated with spinal shock seems promising. Therefore, here we have tested its influence on long-term morphofunctional neurologic outcome. Intravenous L-arginine (300 mg/kg per dose) was administered to adult rats after SCI of moderate intensity according to the following schemes (n=6): (1) single dose at 1 hour, (2) single dose at 24 hour, and (3) repeated doses first at 24 hour and then daily for 7 days. Control injured rats received the vehicle (saline solution). Contrary to our expectations, locomotor function, assessed using the Basso-Beattie-Bresnahan scale for 8 weeks, was significantly worse in the L-arginine treated groups compared with the control group. Areas of both spared white matter and myelin stain at the epicenter seemed reduced in rats that received L-arginine as a single dose at 1 hour after injury but were not significantly different from the control group. L-arginine as used here interfered with the functional outcome of rats subjected to SCI, suggesting that L-arginine or its metabolic products may be neurotoxic. Because of its potential utility for acute SCI suggested in the past, strategies should be designed to block its apparent neurotoxicity.