Combination Of L-arginine Research Articles

L-Arginine in Combination With Sildenafil Potentiates the Attenuation of Hypoxic Pulmonary Hypertension in Rats

Chronic hypoxia induces an increased production of nitric oxide (NO) in pulmonary prealveolar arterioles. Bioavailability of the NO in the pulmonary vessels correlates with concentration of L-arginine as well as activity of phosphodiesterase-5 enzyme (PDE-5). We tested a hypothesis whether a combination of L-arginine and PDE-5 inhibitor sildenafil has an additive effect in reduction of the hypoxic pulmonary hypertension (HPH) in rats. Animals were exposed to chronic normobaric hypoxia for 3 weeks. In the AH group, rats were administered L-arginine during chronic hypoxic exposure. In the SH group, rats were administered sildenafil during chronic hypoxic exposure. In the SAH group, rats were treated by the combination of L-arginine as well as sildenafil during exposure to chronic hypoxia. Mean PAP, structural remodeling of peripheral pulmonary arterioles (%DL) and RV/LV+S ratio was significantly decreased in the SAH group compared to hypoxic controls even decreased compared to the AH and the SH groups in first two measured parameters. Plasmatic concentration of cGMP and NOx were significantly lower in the SAH group compared to hypoxic controls. We demonstrate that NO synthase substrate L-arginine and phosphodiesterase-5 inhibitor sildenafil administered in combination are more potent in attenuation of the HPH compared to a treatment by substances given alone.

The Effects of l-Arginine, Alone and Combined with Vitamin C, on Mineral Status in Relation to its Antidiabetic, Anti-Inflammatory, and Antioxidant Properties in Male Rats on a High-Fat Diet

The aim of this study was to evaluate the influence of the intake of l-arginine alone and of l-arginine with vitamin C on mineral concentration in rats fed with a high-fat diet, and to assess the lipid glucose, insulin, and total antioxidant status (TAS) and tumor necrosis factor (TNF) alpha serum levels that result. Wistar rats were assigned to groups fed with either a standard control diet (C), a diet high in fat (FD), a diet high in fat with l-arginine, or a diet high in fat with l-arginine and vitamin C. After 6 weeks, the length and weight of the rats were measured, and the animals were euthanized. The liver, spleen, kidneys, pancreas, heart, and gonads were collected, as were blood samples. The total serum cholesterol, triglyceride, fasting glucose, insulin, TAS, and TNF alpha levels were measured. The tissue calcium, magnesium, iron, zinc, and copper concentrations were determined. It was found that l-arginine supplementation diminished the effect of the modified diet on the concentration of iron in the liver and spleen and of copper in heart. At the same time, it was observed that l-arginine supplementation reduced the effect of the high-fat diet on insulin, TNF alpha, and TAS. The combination of l-arginine and vitamin C produced a similar effect on the mineral levels in the tissues as did l-arginine used alone. Moreover, positive correlations between serum insulin and iron in the liver, between TNF alpha and iron in the liver, and between TNF alpha and copper in the heart were observed. The level of TAS in serum was inversely correlated with the copper level in the heart and the iron level in the liver. We concluded that the beneficial influence of l-arginine on insulin, TAS, and TNF alpha serum level is associated with changes in the iron and copper status in rats fed with a high-fat diet. No synergistic effect of l-arginine and vitamin C in the biochemical parameters or in the mineral status in rats fed with the modified diet was observed.

Myocardial protection by co-administration of l-arginine and tetrahydrobiopterin during ischemia and reperfusion

BackgroundReduced bioavailability of nitric oxide (NO) is a key factor contributing to myocardial ischemia and reperfusion injury. The mechanism behind the reduction of NO is related to deficiency of the NO synthase (NOS) substrate l-arginine and cofactor tetrahydrobiopterin (BH4) resulting in NOS uncoupling. The aim of the study was to investigate if the combination of l-arginine and BH4 given iv or intracoronary before reperfusion protects from reperfusion injury. MethodsSprague–Dawley rats and pigs were subjected to myocardial ischemia and reperfusion. Rats received vehicle, l-arginine, BH4, l-arginine+BH4 with or without the NOS-inhibitor L-NMMA iv 5min before reperfusion. Pigs received infusion of vehicle, l-arginine, BH4 or l-arginine+BH4 into the left main coronary artery for 30min starting 10min before reperfusion. ResultsInfarct size was significantly smaller in the rats (50±2%) and pigs (54±5%) given l-arginine+BH4 in comparison with the vehicle groups (rats 65±3% and pigs 86±5%, P<0.05). Neither l-arginine nor BH4 alone significantly reduced infarct size. Administration of L-NMMA abrogated the cardioprotective effect of l-arginine+BH4. Myocardial BH4 levels were 3.5- to 5-fold higher in pigs given l-arginine+BH4 and BH4 alone. The generation of superoxide in the ischemic-reperfused myocardium was reduced in pigs treated with intracoronary l-arginine+BH4 versus the vehicle group (P<0.05). ConclusionAdministration of l-arginine+BH4 before reperfusion protects the heart from ischemia–reperfusion injury. The cardioprotective effect is mediated via NOS-dependent pathway resulting in diminished superoxide generation.

Myocardial protection by co-administration of L-arginine and tetrahydrobiopterin during ischemia and reperfusion

Abstract Background Reduced bioavailability of nitric oxide (NO) is a key factor contributing to myocardial ischemia and reperfusion injury. The mechanism behind the reduction of NO is related to deficiency of the NO synthase (NOS) substrate l-arginine and cofactor tetrahydrobiopterin (BH 4 ) resulting in NOS uncoupling. The aim of the study was to investigate if the combination of l-arginine and BH 4 given iv or intracoronary before reperfusion protects from reperfusion injury. Methods Sprague–Dawley rats and pigs were subjected to myocardial ischemia and reperfusion. Rats received vehicle, l-arginine, BH 4 , l-arginine+BH 4 with or without the NOS-inhibitor L-NMMA iv 5min before reperfusion. Pigs received infusion of vehicle, l-arginine, BH 4 or l-arginine+BH 4 into the left main coronary artery for 30min starting 10min before reperfusion. Results Infarct size was significantly smaller in the rats (50±2%) and pigs (54±5%) given l-arginine+BH 4 in comparison with the vehicle groups (rats 65±3% and pigs 86±5%, P 4 alone significantly reduced infarct size. Administration of L-NMMA abrogated the cardioprotective effect of l-arginine+BH 4 . Myocardial BH 4 levels were 3.5- to 5-fold higher in pigs given l-arginine+BH 4 and BH 4 alone. The generation of superoxide in the ischemic-reperfused myocardium was reduced in pigs treated with intracoronary l-arginine+BH 4 versus the vehicle group (P Conclusion Administration of l-arginine+BH 4 before reperfusion protects the heart from ischemia–reperfusion injury. The cardioprotective effect is mediated via NOS-dependent pathway resulting in diminished superoxide generation.

Functional Role for Mouse Cerebellar NO/cGMP/K(ATP)Pathway in Ethanol-Induced Ataxia

We have previously shown that brain adenosine A1 receptors and nitric oxide (NO) play an important role in ethanol (EtOH)-induced cerebellar ataxia (EICA) through glutamate/NO/cGMP pathway. I now report possible modulation of EICA by the cerebellar NO/cGMP/K(ATP) pathway. EICA was evaluated by Rotorod in CD-1 male mice. All drugs (K(ATP) activators pinacidil, 0.05, 0.1, 0.5 nmol; minoxidil, 0.01, 0.1, 1.0 pmol; antagonists glipizide/glibenclamide, 0.01, 0.05, 0.1 nmol; NO donor l-arginine, 20 nmol; NOS inhibitors [iNOS] inhibitor L-NAME, 50 nmol; glutamate, 1.5 nmol; adenosine A1 receptor agonist N(6) -cyclohexyladenosine [CHA], 6, 12 pmol; antagonist DPCPX, 0.1 or 0.4 nmol) were given by direct intracerebellar microinfusion via stereotaxically implanted guide cannulas, except EtOH (2 g/kg, i.p.). Pinacidil and minoxidil dose-dependently accentuated, whereas glipizide and glibenclamide markedly attenuated EICA, indicating tonic participation of K(ATP) channels. Glipizide abolished the pinacidil potentiation of EICA, which confirmed both drugs acted via K(ATP) channels. A possible link between K(ATP) channels and glutamate/NO pathway was suggested when (i) CHA (12 pmol) totally abolished l-arginine-induced attenuation of EICA; (ii) L-NAME abolished l-arginine-induced attenuation of EICA associated with further increase in EICA; and (iii) the combined l-arginine and glutamate infusion virtually abolished EICA. Also, whereas CHA abolished glibenclamide-induced attenuation and potentiated pinacidil/minoxidil-induced accentuation of EICA, the effects of DPCPX were just the opposite to those of CHA. The results with CHA therefore suggest a functional link between K(ATP) and A1 receptors and between K(ATP) and glutamate/NO and as an extension may involve participation of NO/cGMP/K(ATP) pathway in EICA.

Effects of exogenous l-arginine on in vitro rooting, chlorophyll, carbohydrate, and proline concentrations in the sweet cherry rootstock M × M 14 (Prunus avium L. × Prunus mahaleb L.)

The effects of indole-3-butyric acid (IBA) alone and in combination with l-arginine on the morphogenic and biochemical responses in shoot tip explants of the cherry rootstock M × M 14 (Prunus avium × Prunus mahaleb) were examined. The maximum root number per rooted explant (16), root fresh (FW) and dry (DW) weights, as well as the rooting percentage (100 %) were recorded when 2 mg l−1 IBA (alone) were applied. Including the lowest IBA concentration (0.5 mg l−1) with the lowest and highest l-arginine concentrations (0.5 and 2 mg l−1, respectively) resulted in the greatest root length. The maximum leaf chlorophyll concentration and shoot length of the initial explant were recorded when 0.5 mg l−1 IBA plus 2 mg l−1l-arginine were applied. In addition, l-arginine in combination with IBA (1 and 2 mg l−1) was found to suppress shoot FW and DW. On the other hand, l-arginine enhanced the promoting effect of IBA on both root length and leaf chlorophyll concentration. The carbohydrate and proline concentrations in leaves were not significantly altered with the application of IBA alone or in combination with l-arginine. On the other hand, the carbohydrate and proline concentrations in roots were decreased with the application of 1 and 2 mg l−1 IBA with l-arginine, resulting in the suppression of the promoting effects of IBA. It is clear from the findings that l-arginine has a direct effect on the in vitro rooting of M × M 14 explants, is involved in the function of the photosythetic apparatus, influences leaf chlorophyll content, participates in carbohydrate biosynthesis and metabolism, and is involved in proline accumulation both in leaves and roots.

Differential pulsatile secretagogue control of GH secretion in healthy men

Pulsatile growth hormone (GH) secretion putatively reflects integrated regulation by GH-releasing hormone (GHRH), somatostatin (SST), and GH-releasing peptide (GHRP). GHRH and SST secretion is itself pulsatile. However, how GHRH and SST pulses act along with GHRP to jointly determine pulsatile GH secretion is unclear. Moreover, how testosterone (T) modulates such interactions is unknown. These queries were assessed in a prospectively randomized, placebo-controlled double-blind cohort comprising 26 healthy older men randomized to testosterone (T) vs. placebo supplementation. Pulses of GHRH, SST, or saline were infused intravenously at 90-min intervals for 13 h, along with either continuous saline or ghrelin analog (GHRP-2). The train of pulses was followed by a triple stimulus (combined l-arginine, GHRH, and GHRP-2) to estimate near-maximal GH secretion over a final 3 h. Testosterone vs. placebo supplementation doubled pulsatile GH secretion during GHRH pulses combined with continuous saline (GHRH/saline) (P < 0.01). Pulsatile GH secretion correlated positively with T concentrations (270-1,170 ng/dl) in the 26 men during saline pulses/saline (P = 0.015, R(2) = 0.24), GHRH pulses/saline (P = 0.020, R(2) = 0.22), and combined GHRH pulses/GHRP-2 (P = 0.016, R(2) = 0.25) infusions. Basal nonpulsatile GH secretion correlated with T during saline pulses/GHRP-2 drive (P = 0.020, R(2) = 0.16). By regression analysis, pulsatile GH secretion varied negatively with body mass index (BMI) during saline/GHRP-2 infusion (P = 0.001, R(2) = 0.36), as well as after the triple stimulus preceded by GHRH/GHRP-2 (P = 0.013, R(2) = 0.23). Mean (10-h) GH concentrations under GHRP-2 were predicted jointly by estradiol (positively) and BMI (negatively) (P < 0.001, R(2) = 0.520). These data indicate that estradiol, T, and BMI control pulsatile secretagogue-specific GH-regulatory mechanisms in older men.

Effects of nucleotides adenosine monophosphate and adenosine triphosphate in combination with L‐arginine on male rabbit corpus cavernosum tissue

Purines and more specifically adenosine monophosphate (AMP) and adenosine triphosphate (ATP) have a strong relaxant effect on smooth muscle cells of the dog, rabbit and human corpus cavernosum, to approximately the same degree as nitric oxide (NO). However, purines are considered as modulators of erectile function rather than key mediators. This suggests that the use of purines combined with NO donors could be effective to treat some specific erectile disorders. The relaxation induced by the combination of l-arginine (Arg), a natural substrate for NO synthase, was assessed with a purine-nucleotide (AMP, ATP) on a rabbit corpus cavernosum model, to determine if these substances could potentiate each other's effect. When a pre-contraction was induced by phenylephrine, AMP alone induced a 43% CC relaxation rate and ATP alone a 26% rate. The relaxation rate induced by Arg was lower in comparison (8% at 5.10(-4) m vs. 25% at AMP 5.10(-4) m and 15% at ATP 5.10(-4) m). NO synthase inhibitor n-nitro-l-arginine did not modify the relaxing effect provoked by AMP suggesting that the mechanism of action of this nucleotide does not involve the NO pathway. The combination of Arg at 5.10(-4) m with either AMP or ATP at different doses ranging from 5.10(-4) to 10(-3) m significantly enhanced the relaxing response reaching rates of 62 and 80% respectively, leading to a synergistic effect. The present data indicate that a 'NO donor' combined with an 'adenosine donor' could be an effective therapeutic approach.

Effect of Supplementation During Pregnancy With l-Arginine and Antioxidant Vitamins in Medical Food on Preeclampsia in High-Risk Population: Randomized Controlled Trial

No effective preventive measures for preeclampsia and eclampsia have been identified despite intensive investigation. Defective synthesis of a key vasodilator, nitric oxide, has been demonstrated in patients with preeclampsia. Circulating l-arginine is a substrate for nitric oxide synthesis during pregnancy; preliminary data suggest that supplemental l-arginine in the diet may lower the risk of preeclampsia during pregnancy by promoting vasodilatation through increased production of nitric oxide. Based on limited data from clinical trials, it has been proposed that antioxidants may also act as prophylactic agents for preeclampsia. This randomized, blinded, placebo-controlled clinical trial tested the hypothesis that a deficiency in l-arginine may be associated with the development of preeclampsia in a population of pregnant women at high risk for this condition. The effect of dietary supplementation with a combination of l-arginine and antioxidant vitamins on the risk of preeclampsia was investigated in this population. The study subjects were 672 pregnant women at 14 to 32 weeks of gestation who were at high risk because of a personal history of preeclampsia or preeclampsia in a first-degree relative. The women were divided into the following 3 groups: (1) a placebo group (n = 222), (2) an antioxidant vitamins plus l-arginine group (n = 228), and (3) an antioxidant vitamins alone group (n = 222). Participants had a clinical follow-up visit every 3 to 4 weeks until delivery. There was a significantly lower incidence of preeclampsia among pregnant women receiving dietary supplementation with l-arginine plus antioxidant vitamins (13%) compared with placebo (30%, P < 0.001), with a relative risk (RR) of 0.42 (95% confidence interval [CI], 0.28–0.62). Antioxidant vitamins alone (23%) had no statistically significant effect on risk of preeclampsia compared with placebo (P = 0.052; RR, 0.74; 95% CI, 0.54–1.02). Compared with vitamins alone, l-arginine plus antioxidant vitamins was associated with a significant reduction in the risk of preeclampsia (P = 0.004); the RR was 0.56, with a 95% CI of 0.37 to 0.85. Side effects were significantly more frequent in the l-arginine plus antioxidant vitamins group than in the placebo group (P = 0.019), but no patient withdrew from the study as a result of adverse effects. These findings show that dietary supplementation with l-arginine and antioxidant vitamins reduces the incidence of preeclampsia in a population of pregnant women at high risk for the disease.

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 combination of l-arginine and ischaemic post-conditioning at the onset of reperfusion limits myocardial injury in the pig

To investigate whether ischaemic post-conditioning (IPoC) combined with i.v. infusion of the nitric oxide (NO) substrate L-arginine at the onset of reperfusion exerts cardioprotective effect that is superior to either treatment given separately. Twenty-six anesthetized pigs were subjected to coronary artery (left anterior descending artery, LAD) ligation for 40 min followed by 4 h reperfusion. The pigs were randomized into five different groups receiving either i.v. vehicle, i.v. L-arginine, IPoC 4 × 60 s together with i.v. vehicle or IPoC together with i.v. L-arginine and a group with IPoC 8 × 30 s. All infusions were started 10 min before reperfusion. The infarct size of the vehicle group was 82 ± 4% of the area at risk. L-Arginine alone (79 ± 8%), IPoC 4 × 60 s vehicle (86 ± 3%) or IPoC 8 × 30 s vehicle (94 ± 7%) did not affect infarct size. l-Arginine together with IPoC significantly reduced infarct size to 59 ± 4% (P < 0.01). Except for higher LAD flow during early reperfusion in the IPoC L-arginine group, haemodynamic parameters did not differ between the four main groups. Heart rate and rate pressure product were lower during ischaemia and reperfusion in the IPoC 8 × 30 s vehicle group. In comparison with the vehicle group, there were no changes in the expression of Akt, phosphorylated Akt Ser(473) , inducible NO synthase, endothelial NO synthase (eNOS) or phosphorylated eNOS Ser(1177) in the ischaemic/reperfused myocardium. L-Arginine given systemically at the onset of reperfusion protects the pig heart against ischaemia and reperfusion injury only when combined with IPoC. These results indicate that the combination of the two treatment strategies exerts cardioprotection.

L-Arginine and Antioxidant Diet Supplementation Partially Restores Nitric Oxide-Dependent Regulation of Phenylephrine Renal Vasoconstriction in Diabetics Rats

The increase of reactive oxygen species (ROS) in diabetes potentiates the vascular effects of phenylephrine through nitric oxide (NO) impairment, facilitating the development of diabetic nephropathy. We propose that the combination of an antioxidant and L-arginine as diet supplements could prevent the increased vascular response to phenylephrine in diabetic animals. Changes in the adrenergic system play an important role in the development of vascular complications in the prediabetic condition. The vasoconstrictor effects of phenylephrine are regulated by NO, and the impairment of endothelium-dependent vasodilation in diabetes is associated with ROS. Diabetes was induced with a low dose (55 mg/kg body weight) of streptozotocin in 7-week-old rats. Diabetic rats were fed with a diet supplement containing a combination of vitamin E, vitamin C, eicosapentaenoic acid, docosahexaenoic acid, and L-arginine, and the effects on phenylephrine-induced renal vascular responses were evaluated. Phenylephrine increased the renal perfusion pressure of isolated perfused kidneys from diabetic rats compared with nondiabetic rats. This effect was associated with reduced nitrite release as well as reduced plasma tetrahydrobiopterin and increased superoxide anions in the renal tissue. Diet supplementation with a combination of L-arginine and vitamins in diabetic rats partially prevented the generation of superoxide associated with recovery of the renal release of NO and decreased phenylephrine-induced vasoconstrictor effects, compared with untreated diabetic rats. However, the administration of L-arginine or vitamins alone did not affect phenylephrine-induced vasoconstriction. Vitamin treatment alone did decrease superoxide generation. The protective mechanism of NO on the vasoconstrictor effects of phenylephrine in the kidney is lost during the development of diabetes, probably via the actions of ROS through a decrease in tetrahydrobiopterin, thus contributing to the pathogenesis of diabetic nephropathy. Restoration of this protective NO mechanism can be achieved by simultaneously stimulating NO synthesis and preventing the effects of ROS through the use of L-arginine and a combination of vitamins E and C as diet supplementation.

A Possible Role for Gastroprotectives on Aspirin-Induced Gastric Ulcer in Rats

Background: Gastric ulcer is a discontinuity in the gastric mucosa that occurs due to imbalance between gastric mucosal protective factors and aggressive factors. The Aim of the present work was to test and compare the protective effects of an antisecretory H 2 receptor blocker; ranitidine and other recently suggested gastroprotective drugs: L-arginine; a precursor of NO, zinc sulfate; an anti-inflammatory antioxidant agent and pioglitazone; a PPAR-g agonist, on a rat model of aspirin induced gastric ulcer. Methods: Acute gastric lesion was induced in rats by a single oral dose of aspirin 300mg/ kg body weight. L-arginine 200mg / kg b. wt, zinc sulfate 80 mg/ kg b. wt, and pioglitazone 10 mg / kg b. wt. were given alone and in combination with ranitidine 50 mg / kg b. wt for 3 days before induction of gastric lesion. Results: Aspirin induced a significant increase in gastric mucosal lesion score and free and total gastric hydrochloric acid with a significant decrease in gastric nitric oxide and mucin levels as compared to normal group. A significant increase in gastric malondialdhyde and decrease in reduced glutathione as compared to normal group. L-arginine, zinc sulfate, and pioglitazone produced improvement of most of the measured parameters as compared to non-treated group. Combination of L-arginine and ranitidine was superior in prophylaxis against aspirin-induced gastric ulcer when compared to the effects of each drug used individually, and the other studied combinations. Conclusion: The role of HCl and NO seems more important in the pathogenesis of aspirin induced gastric ulcer, as evidenced by the better protective effects of combination of ranitidine and L-arginine in comparison to the ranitidine with either zinc sulfate or pioglitazone.

L-Arginine enhances the triglyceride-lowering effect of simvastatin in patients with elevated plasma triglycerides

We recently noticed a possible triglyceride-lowering effect during dietary supplementation with L-arginine. The major limitation of prior studies on L-arginine, however, was that triglyceride levels were not the primary end point, and patients were not necessarily hypertriglyceridemic. Therefore, we conducted a 2-arm, randomized, double-blind study in 33 hypertriglyceridemic patients to investigate the hypothesis that oral L-arginine may lower serum triglyceride levels in hypertriglyceridemic patients on and off statins. The study consisted of a 6-week run-in phase, 6 weeks of treatment with L-arginine (n = 22, 1.5 g bid) or placebo (n = 11), and a 6-week extension period where simvastatin (20 mg qd) was added. All patients received dietary advice during each study visit. Routine and lipid laboratory parameters were determined in the local routine clinical laboratory. Treatment with L-arginine alone had no effects on serum lipids compared to placebo. The combination of L-arginine with simvastatin led to a significantly stronger reduction in triglycerides compared to placebo plus simvastatin (-140.5 +/- 149.2 mg/dL vs -56.1 +/- 85.0 mg/dL; P = .048). In addition, we found simvastatin-induced increases in aspartate transaminase and fibrinogen to be attenuated by L-arginine as compared to placebo. We conclude from our data that L-arginine enhances the effects of simvastatin on lipid metabolism, but it has no triglyceride-lowering effects when given alone.

Effect of Nitric Oxide/Cyclic Guanosine Mono-phosphate Pathway on Gallbladder Relaxant Response in Bile Duct-Ligated Guinea Pigs

Background/Aims: Common bile duct ligation (CBDL) in the guinea pig is a well-defined model of acalculous cholecystitis. Nitric oxide (NO) mediates smooth muscle relaxation by stimulating the activity of soluble guanylate cyclase. The aim of this study was to determine whether the NO/cyclic guanosine monophosphate pathway plays a role in gallbladder relaxant response after CBDL. Methods: Relaxant response of gallbladder muscle strips from CBDL and sham-operated guinea pigs was studied in vitro. Animals were treated with saline, aminoguanidine or an aminoguanidine + L-arginine combination in vivo. Concentration-response curves of papaverine, diethylamine/NO, YC-1, sildenafil and amrinone were obtained and relaxations in each group were calculated as the percent of the contractions induced by carbachol (10^–6 M). Results: There was a significant decrease in the gallbladder muscle relaxant responses to these substances in CBDL and aminoguanidine groups compared with sham surgical controls. The decreased relaxant response was reversed by aminoguanidine + L-arginine but not by aminoguanidine alone. Conclusion: Decreased relaxant responses might be due to the reduced guanylate cyclase enzyme activity, but further studies are required.

L-Arginine as a factor increasing arginase significance in diagnosis of primary and metastatic colorectal cancer

Objective The usefulness of simultaneous l-arginine and arginase determination in diagnosis of primary and metastatic colorectal cancer. Methods l-Arginine and arginase were determined before and after surgery in serum from 43 patients with colorectal cancer (CRC), 24 with colorectal cancer liver metastasis (CRCLM), and 39 control subjects (10 patients with non-malignant diseases and 29 healthy blood donors). Results Preoperative l-arginine concentration in the patient groups was 2-fold higher, whereas arginase activity was over 3- and 6-fold higher in CRC and CRCLM when compared with control. The values of both parameters lowered significantly after surgery. The sensitivity of single parameter in CRC was 79% for l-arginine and 81% for arginase, and in CRCLM it was 83% for each parameter. The combination of l-arginine with arginase improved the sensitivity to 93% and 100% in CRC and CRCLM, respectively. The specificity of l-arginine and arginase calculated for 39 subjects was 87% and 82%. Conclusion Simultaneous determination of l-arginine and arginase increases the value of arginase itself in diagnosis and follow up of patients with CRC and CRCLM.

Effects of NO/L-Arginine Pathway on Gallbladder Contractility in Bile Duct Ligated Guinea Pigs

Common bile duct ligation (CBDL) produces gallbladder distension and acute inflammation similar to that seen in human acute acalculous cholecystitis. CBDL in the guinea pig affects smooth muscle contractility. The aim of this study was to determine whether the nitric oxide-L-arginine pathway plays a role in the inflammatory process and abnormal gallbladder contractility that occur after CBDL. Contractility of gallbladder muscle from CBDL and sham-operated guinea pigs was studied in vitro. Animals were treated with saline, aminoguanidine (AG), or an aminoguanidine + L-arginine combination (AG + L-Arg) in vivo. Potassium chloride, carbachol, and electric field stimulation (EFS) were used for contracting the gallbladder muscle strips or activating intrinsic nerves. Hematoxylin and eosin-stained slides of muscle strips were scored for inflammation. Contraction responses to carbachol and EFS were decreased significantly in CBDL guinea pigs compared with those in the sham-operated group. AG partly reversed the smooth muscle contractile response to carbachol and EFS, but did not reduce the inflammation score. Treatment with AG + L-arg did not reverse either the contraction response or the inflammation score. These findings suggest that AG and AG + L-Arg treatments have no beneficial effect on inflammation in guinea pigs after CBDL, although AG significantly reversed the effect on muscle contractility (P < 0.05). This improvement was independent of inflammation and may be due to a decreased level of NO and its diminished relaxant effect.

Synergistic Protection of L-Arginine and Vitamin E On Lipid Peroxidation of Asthenospermic Patients

Background: Lipid peroxidation is known to cause various impairments to sperm cells and may play a major role in the etiology of male infertility. Asthenospermia is the main factor of male infertility and has significantly higher level of peroxidation than in normozoospermic males. Materials and Methods: Using thiobarbituric acid (TBA) assay procedure, we have determined the level of lipid peroxidation as indicated by malondialdehyde (MDA) in the spermatozoa obtained from asthenospermic male semen. Results: An inverse correlation of MDA concentration with sperm motility is observed. Treatment of cells with L-arginine and vitamin E significantly decreases the MDA concentration and improves the sperm motility as compared to that in case of control samples. A combination of L-arginine and vitamin E shows synergistic effect on sperm motility and prevention of lipid peroxidation. Conclusion: L-arginine and vitamin E protect the cells against the loss of sperm motility by lipid peroxidation. Therefore, supplementation of both L-arginine and vitamin E may improve sperm motility and increase the possibility of fertilization in asthenospermic subjects.

Polyaspartoyl· l-arginine inhibits platelet aggregation through stimulation of NO release from endothelial cells

Polyaspartoyl· l-arginine (PDR) is an inhibitor of platelet aggregation ex vivo but in vitro. This study attempts to elucidate the target cell of PDR action and its action mechanism. PDR (1.7–170 µg/ml) significantly inhibited platelet aggregation in vitro in the presence of rat aortic endothelial cells (RAEC), NO synthase inhibitor N-nitro- l-arginine methyl ester ( l-NAME) inhibited this effect, but it was ineffective in the RAEC absence. Correspondingly, PDR increased NO level in the supernatants of the platelet reactants in RAEC presence, but failed to influence NO level in RAEC absence, and these effects of PDR were more potent than those of l-arginine. Furthermore, PDR markedly elevated the intracellular level of l-arginine, and it (17–170 µg/ml) also augmented l-citrulline level in RAEC, argininosuccinate lyase (ASL) inhibitor succinate enhanced its effect on l-citrulline but l-NAME weakened it. 170 µg/ml of PDR slightly increased the l-aspartate level in RAEC, and succinate enhanced this effect. However l-arginine, l-aspartate or the combination of l-arginine and l-aspartate failed to change levels of these amino acids. In addition, PDR (170 μg/ml) stimulated the expression of argininosuccinate synthetase (ASS) protein. In conclusion, the endothelial cell is direct target cell of PDR's action; PDR facilitates the entry of l-arginine by serving as a carrier of l-arginine into RAEC; it also supplies aspartic acid and stimulates ASS expression, and then enhances the intracellular citrulline–NO cycle, thus increases the availability of l-arginine and NO synthesis. Therefore the effect of PDR on platelet aggregation is primarily attributed to its stimulation of NO synthesis in endothelial cells; PDR may be a better cardiovascular protective agent than l-arginine.

Kidney damage after renal ablation is worsened in endothelial nitric oxide synthase (−/−) mice and improved by combined administration of L‐arginine and antioxidants

Reduction in nitric oxide (NO) levels during kidney failure has been related to the reaction of NO with superoxide anions to yield peroxynitrite which possesses the biological activity responsible for renal damage. However, stimulation of the NO pathway ameliorates the progression of kidney failure. Thus, it is unclear whether NO prevents or acts as the compound responsible for the cytotoxicity observed during kidney failure. We evaluated the development of kidney failure in animals that were wild type and deficient in endothelial NO synthase (eNOS -/-) and tested the effects of an antioxidant treatment and NO precursors on the generation of superoxide anion and kidney failure parameters. In wild-type mice, five-sixths nephrectomy increased proteinuria from 3.0 +/- 0.35 to 14.5 +/- 0.76 mg protein/24 h (P < 0.05), blood pressure from 83.1 +/- 1.8 to 126.6 +/- 1.7 mmHg (P < 0.05), and superoxide production from 1.4 +/- 0.6% to 74.3 +/- 0.8% (P < 0.05). The effects of five-sixths nephrectomy on the eNOS -/- mice were greater compared with wild-type mice. Proteinuria increased from 6.7 +/- 0.5 to 22.7 +/- 2.0 mg protein/24 h (P < 0.05), blood pressure increased from 93.3 +/- 0.9 to 151.2 +/- 3.4 mmHg (P < 0.05), and superoxide production increased from 12.9 +/- 0.5% to 99.8 +/- 1.3% (P < 0.05). The nitrotyrosine levels were lower in eNOS -/- mice as compared to wild-type mice. A combination of L-arginine and antioxidant treatment ameliorated renal damage. The effect was improved in wild-type animals. Our data support the relevance of NO as an antagonist to superoxide in renal tissues and suggest that the loss of this mechanism promotes the progression of kidney failure.