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Physical activity affects the vasculature through mechanisms related to nitric oxide bioavailability, oxidative stress, and inflammation; with endothelial function at the centre of this triad. In a South African setting, with the prevalence of hypertension and physical inactivity being alarmingly high, we aimed to investigate relationships of vascular function with markers of oxidative stress, inflammation and nitric oxide synthesis capacity in physically active and inactive groups. Based on the 2010 World Health Organisation guidelines, black and white school teachers were divided into physically active (n= 84) and physically inactive (n= 132) groups. Twenty-four-hour blood pressure (24 h BP), total peripheral resistance and Windkessel compliance were measured. Markers of oxidative stress, inflammation and nitric oxide synthesis capacity were analysed. Windkessel compliance (p= 0.041) and homoarginine (p= 0.006) were higher in the physically active group. In the same group, 24 h diastolic BP associated with total glutathione (β = 0.17; p= 0.056), and 24 h BP (systolic blood pressure: β = 0.23, p= 0.006; diastolic blood pressure: β = 0.22, p= 0.019) associated with homoarginine. In the physically inactive group, 24 h BP (systolic blood pressure: β = 0.26, p< 0.001; diastolic blood pressure: β = 0.23, p= 0.007) associated with symmetric dimethylarginine (SDMA). These associations were independent of inflammation. Despite only reaching moderate physical activity levels, vascular function and nitric oxide synthesis capacity were more favourable in the physically active population compared to the physically inactive population. These results may suggest that even moderate physical activity could increase nitric oxide synthesis capacity, which in turn may mitigate the development of cardiovascular disease in this population.

AbstractObjective:Elevated levels of arginine derivatives in the NO pathway, such as asymmetric dimethylarginine (ADMA), are related to disease severity and reduced exercise capacity in heart failure (HF). We investigated the influence of exercise intervention on these parameters and on L-arginine (L-Arg) and L-homoarginine (L-hArg) in HF with preserved ejection fraction (HFpEF) patients.Material and methods:Sixty-two patients (65 ± 6 years) were included in this analysis and randomized to supervised endurance/resistance training (ET) or to usual care (UC). EDTA-plasma was analysed for NO metabolites.Results:There were baseline associations for adjusted values of maximum workload with ADMA (r= −0.322, p = 0.028) and L-Arg/ADMA ratio (r = 0.331, p = 0.015), and for the 6-min walk test (6MWT) with ADMA (r= −0.314, p = 0.024) and L-Arg/ADMA ratio (r = 0.346, p = 0.015). No significant differences between UC and ET changes of NO parameters were observed at 3-month follow-up. Higher L-hArg levels were associated with a greater improvement in peak oxygen uptake (peak O2) at follow-up: 3.4 ± 2.8 vs. 1.1 ± 2.9 mL/min/kg (p = 0.005).Conclusions:Exercise intervention did not influence NO parameters in HFpEF patients, but L-hArg was related to change in peak O2.

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Nitroxyl (HNO) donors have potential benefit in the treatment of heart failure and other cardiovascular diseases. 1-Nitrosocyclohexyl acetate (NCA), a new HNO donor, in contrast to the classic HNO donors Angeli’s salt and isopropylamine NONOate, predominantly releases HNO and has a longer half-life. This study investigated the vasodilatative properties of NCA in isolated aortic rings and human platelets and its mechanism of action. NCA was applied on aortic rings isolated from wild-type mice and apolipoprotein E–deficient mice and in endothelial-denuded aortae. The mechanism of action of HNO was examined by applying NCA in the absence and presence of the HNO scavenger glutathione (GSH) and inhibitors of soluble guanylyl cyclase (sGC), adenylyl cyclase (AC), calcitonin gene-related peptide receptor (CGRP), and K+channels. NCA induced a concentration-dependent relaxation (EC50, 4.4 µM). This response did not differ between all groups, indicating an endothelium-independent relaxation effect. The concentration-response was markedly decreased in the presence of excess GSH; the nitric oxide scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide had no effect. Inhibitors of sGC, CGRP, and voltage-dependent K+channels each significantly impaired the vasodilator response to NCA. In contrast, inhibitors of AC, ATP-sensitive K+channels, or high-conductance Ca2+-activated K+channels did not change the effects of NCA. NCA significantly reduced contractile response and platelet aggregation mediated by the thromboxane A2mimetic 9,11-dideoxy-11α,9α-epoxymethanoprostaglandin F2αin a cGMP-dependent manner. In summary, NCA shows vasoprotective effects and may have a promising profile as a therapeutic agent in vascular dysfunction, warranting further evaluation.

Nitroxyl (HNO) donors have potential benefit in the treatment of heart failure and other cardiovascular diseases. 1-Nitrosocyclohexyl acetate (NCA), a new HNO donor, in contrast to the classic HNO donors Angeli's salt and isopropylamine NONOate, predominantly releases HNO and has a longer half-life. This study investigated the vasodilatative properties of NCA in isolated aortic rings and human platelets and its mechanism of action. NCA was applied on aortic rings isolated from wild-type mice and apolipoprotein E-deficient mice and in endothelial-denuded aortae. The mechanism of action of HNO was examined by applying NCA in the absence and presence of the HNO scavenger glutathione (GSH) and inhibitors of soluble guanylyl cyclase (sGC), adenylyl cyclase (AC), calcitonin gene-related peptide receptor (CGRP), and K(+) channels. NCA induced a concentration-dependent relaxation (EC(50), 4.4 µM). This response did not differ between all groups, indicating an endothelium-independent relaxation effect. The concentration-response was markedly decreased in the presence of excess GSH; the nitric oxide scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide had no effect. Inhibitors of sGC, CGRP, and voltage-dependent K(+) channels each significantly impaired the vasodilator response to NCA. In contrast, inhibitors of AC, ATP-sensitive K(+) channels, or high-conductance Ca(2+)-activated K(+) channels did not change the effects of NCA. NCA significantly reduced contractile response and platelet aggregation mediated by the thromboxane A(2) mimetic 9,11-dideoxy-11α,9α-epoxymethanoprostaglandin F(2)(α) in a cGMP-dependent manner. In summary, NCA shows vasoprotective effects and may have a promising profile as a therapeutic agent in vascular dysfunction, warranting further evaluation.

ABSTRACTThe objective of this study was to identify the oral pathogens found in odontogenic infections, to determine their susceptibilities to amoxicillin-clavulanic acid (AMC), clindamycin (CLI), doxycycline (DOX), levofloxacin (LVX), moxifloxacin (MXF), and penicillin (PEN), and to search for associations between specific pathogens and types of infection. Swabs from patients enrolled in a randomized, double-blind phase II trial comparing MXF with CLI for the treatment of odontogenic abscesses or inflammatory infiltrates were cultured on media for aerobes and anaerobes. All bacterial isolates were identified at the species level. Overall, 205 isolates were cultured from 71 patients: 77 viridans group streptococci, 56 Prevotellaspp., 19 Neisseriaspp., 17 Streptococcus anginosusgroup isolates and hemolytic streptococci, 15 other anaerobes, and 21 other bacteria. Ninety-eight percent of pathogens were susceptible to MXF, 96% to AMC, 85% to LVX, 67% to PEN, 60% to CLI, and 50% to DOX. S. anginosusgroup and hemolytic streptococci were found significantly more frequently (P= 0.04) in patients with abscesses (12/95) than in patients with infiltrates (5/110). In four patients with infiltrates who failed to respond to CLI therapy, three isolates of the Streptococcus mitisgroup and four Neisseriaspp. resistant to CLI were found. In this study, S. anginosusgroup and hemolytic streptococci were clearly associated with odontogenic abscesses. Our analysis suggests that viridans group streptococci and Neisseriaspp. play a decisive role in the etiology of odontogenic infiltrates. The high in vitroactivity of MXF against odontogenic bacteria corresponds well to its clinical results in the treatment of odontogenic abscesses and infiltrates.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases. By inhibiting nitric oxide formation, ADMA causes endothelial dysfunction, vasoconstriction, elevation of blood pressure, and aggravation of experimental atherosclerosis. Levels of ADMA and its isomer symmetric dimethylarginine (SDMA), which does not inhibit nitric oxide synthesis, are both elevated in patients with kidney disease. Currently available data from prospective clinical trials in patients with chronic kidney disease suggest that ADMA is an independent marker of progression of renal dysfunction, vascular complications and death. High SDMA levels also negatively affect survival in populations at increased cardiovascular risk, but the mechanisms underlying this effect are currently only partly understood. Beyond glomerular filtration, other factors influence the plasma concentrations of ADMA and SDMA. Elevated plasma concentrations of these dimethylarginines might also indirectly influence the activity of nitric oxide synthases by inhibiting the uptake of cellular L-arginine. Other mechanisms may exist by which SDMA exerts its biological activity. The biochemical pathways that regulate ADMA and SDMA, and the pathways that transduce their biological function, could be targeted to treat renal disease in the future.

Objective: Conjugated linoleic acid (CLA) showed a wide range of beneficial biological effects with relevance for cardiovascular health in animal models and humans. Most human studies used olive oil as a reference. This study assessed the effect of CLA as compared with safflower oil on endothelial function and markers of cardiovascular risk in overweight and obese men. Heated safflower oil and olive oil were given for additional descriptive control.Methods: Eighty-five overweight men (aged 45–68 years, body mass index 25–35 kg/m2) were randomized to receive 4.5 g/d of the CLA isomeric mixture, safflower oil, heated safflower oil, or olive oil in a 4-week double-blind study. Endothelial function was assessed by peripheral arterial tonometry (PAT) index determination in the fasting and postprandial state (i.e., 4 hours after consumption of a fat- and sucrose-rich meal).Results: CLA as compared with safflower oil consumption did not impair fasting or postprandial PAT index but decreased body weight. CLA as compared with safflower oil did not change total, low-density lipoprotein (LDL), or high-density lipoprotein (HDL) cholesterol; triglycerides; insulin sensitivity indices; C-reactive protein; soluble adhesion molecules; oxidized LDL; lipoprotein a (Lp[a]); paraoxonase; or platelet-activating factor acetylhydrolase (PAF-AH) activity, but significantly reduced arylesterase activity and increased concentrations of the F2-isoprostane 8-iso-prostaglandin F (PGF)2α.Conclusion: CLA did not impair endothelial function. Other parameters associated with metabolic syndrome and oxidative stress were not changed or were slightly improved. Results suggest that CLA does not increase cardiovascular risk. Increased F2-isoprostane concentrations in this context may not indicate increased oxidative stress.

ABSTRACTMoxifloxacin penetrates well into oromaxillary tissue and covers the causative pathogens that show an increasing resistance to standard antibiotics. Clinical reports suggest that moxifloxacin may be effective for the treatment of odontogenic infections that can lead to serious complications. The objective of this prospective, randomized, double-blind, multicenter study was to compare the efficacies and safeties of moxifloxacin and clindamycin for the medical treatment of patients with gingival inflammatory infiltrates and as an adjuvant therapy for patients with odontogenic abscesses requiring surgical treatment. Patients received either 400 mg moxifloxacin per osonce daily or 300 mg clindamycin per osfour times daily for 5 days consecutively. The primary efficacy endpoint was the percent reduction in patients' perceived pain on a visual analogue scale at days 2 to 3 from baseline. Primary analysis included 21 moxifloxacin- and 19 clindamycin-treated patients with infiltrates and 15 moxifloxacin- and 16 clindamycin-treated patients with abscesses. The mean pain reductions were 61.0% (standard deviation [SD], 46.9%) with moxifloxacin versus 23.4% (SD, 32.1%) with clindamycin (P= 0.006) for patients with infiltrates and 55.8% (SD, 24.8%) with moxifloxacin versus 42.7% (SD, 48.5%) with clindamycin (P= 0.358) for patients with abscesses. A global efficacy assessment at days 2 to 3 and 5 to 7 showed faster clinical responses with moxifloxacin in both abscess and infiltrate patients. Rates of adverse events were lower in moxifloxacin- than in clindamycin-treated patients. In patients with inflammatory infiltrates, moxifloxacin was significantly more effective in reducing pain at days 2 to 3 of therapy than clindamycin. No significant differences between groups were found for patients with odontogenic abscesses.

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is increasingly recognized as a novel biomarker in cardiovascular disease. To date, it remains unclear whether elevated ADMA levels are merely associated with cardiovascular risk or whether this molecule is of functional relevance in the pathogenesis of atherosclerotic vascular disease. To clarify this issue, we crossed dimethylarginine dimethylaminohydrolase (DDAH) transgenic mice that overexpress the human isoform 1 of the ADMA degrading enzyme DDAH into ApoE-deficient mice to generate ApoE−/−/hDDAH1+/−mice. In these mice, as well as ApoE−/−wild-type littermates, atherosclerosis within the aorta as well as vascular function of aortic ring preparations was assessed. We report here that overexpression of hDDAH1 reduces plaque formation in ApoE−/−mice by lowering ADMA. The extent of atherosclerosis closely correlated with plasma ADMA levels in male but not female mice fed either a standard rodent chow or an atherogenic diet. Functional analysis of aortic ring preparations revealed improved endothelial function in mice overexpressing hDDAH1. Our findings provide proof-of-principle that ADMA plays a causal role as a culprit molecule in atherosclerosis and support recent evidence indicating a functional relevance of DDAH enzymes in genetic mouse models. Together, these results demonstrate that pharmacological interventions targeting the ADMA/DDAH pathway may represent a novel approach in the prevention and management of cardiovascular diseases.

Importance of the field:Telmisartan belongs to the angiotensin II type 1 (AT1) receptor antagonizing class of antihypertensives, which are widely recognized and increasingly prescribed because of their good tolerability. Moreover, due to the results of the ONTARGET trial program, telmisartan was the first AT1 receptor antagonist to receive approval for the prevention of cardiovascular events in cardiovascular high risk patients, thereby, indicating that its clinical importance will further increase.Areas covered in this review:This article reviews the pharmacokinetic and pharmacodynamic properties of telmisartan with a special focus on novel pharmacokinetic characteristics of the drug.What the reader will gain:An overview of the published data regarding the pharmacokinetic properties of telmisartan as well as a summary of the results from selected small exploratory and large clinical outcome trials involving telmisartan.Take home message:Telmisartan is a safe and effective alternative for the treatment of hypertension. Moreover, due to its good tolerability, an increasing use of telmisartan in cardiovascular high risk patients can be anticipated. This will grant further experimental and clinical research on AT1 receptor-independent pharmacodynamics of telmisartan as well as on telmisartan-related drug safety issues.

Asymmetrical dimethylarginine (ADMA), an inhibitor of endothelial nitric oxide synthase, is a marker of endothelial dysfunction. Elevated circulating ADMA concentrations have been associated with systemic and carotid atherosclerosis, an elevated risk of developing stroke, and magnetic resonance imaging white-matter hyperintensities (WMHs). The relation of plasma ADMA to subclinical vascular brain injury has not been previously studied in a middle-aged, community-based sample.

Higher plasma concentrations of the endogenous nitric oxides synthase inhibitor asymmetrical dimethylarginine (ADMA) are associated with increased risk of cardiovascular and cerebrovascular events and death, presumably by promoting endothelial dysfunction and subclinical atherosclerosis. We hypothesized that plasma ADMA concentrations are positively related to common carotid artery intimal-media thickness (CCA-IMT) and to internal carotid (ICA)/bulb IMT.

L-Arginine is the precursor for nitric oxide synthesis. In the brain, nitric oxide acts as a neurotransmitter; in the immune system, nitric oxide acts as a mediator of host defense; in the cardiovascular system, nitric oxide mediates the protective effects of the intact endothelium, acting as an endogenous antiatherogenic molecule.

Hypertension is a cardiovascular risk factor commonly associated with endothelial dysfunction and increased renal vascular resistance. Angiotensin receptor blockers (ARBs) may beneficially affect these parameters via antagonism of angiotensin type 1 (AT1) receptor-mediated vasoconstriction and vascular superoxide production. We therefore investigated whether the new ARB telmisartan improves endothelial function and renal vascular resistance in patients with essential hypertension.

L-Arginine, the substrate for nitric oxide synthase, is the precursor for nitric oxide synthesis in the vascular endothelium. Experimental and preliminary clinical studies have indicated that intra-arterial or intravenous infusion ofL-arginine could improve nitric oxide bioavailability in the coronary arteries. Here, Tousoulis et al. examine the literature on the role of L-arginine in the prevention of atherosclerosis from a clinical perspective.

The malononitrilamide FK778 is a novel derivate of leflunomide and interacts with T- and B-cell function by inhibiting de novo pyrimidine synthesis. We investigated the effects of FK778 upon acute cardiac allograft rejection and upon adhesion molecule upregulation in experimental transplantation and by using in vitro cell culture.

The adhesion of monocytes to vascular endothelium increases in the presence of high levels of low density lipoprotein (LDL). LDL changes oxidative status of endothelial cells leading to an increased expression of cell adhesion molecules. Acetylsalicylic acid (ASA) has been shown to exert antioxidant effects in high and very high concentrations. This study was designed to demonstrate the influence of acetylsalicylic acid and its major metabolite, salicylic acid (SA), on the adhesion of monocytes to LDL-stimulated endothelial cells.

Today, the lifetime risk of patients aged 55 – 65 years to receive antihypertensive drugs approaches 60%. Yet, recent trials suggest that hypertension is not adequately controlled in the majority of patients. The prevalence of hypertension increases with advancing age, as does the prevalence of comorbid conditions and the total number of medications taken. Multi-drug therapy, advancing age and comorbid conditions are also key risk factors for adverse drug reactions and drug interactions. In this review, the authors evaluate the most frequently used antihypertensive drugs (diuretics, β-adrenergic blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, angiotensin II receptor Type 1 blockers and α-adrenergic blockers) with special reference to pharmacodynamic and pharmacokinetic drug interactions. As the spectrum of drugs prescribed is constantly changing, safety yesterday does not imply safety today and safety today does not imply safety tomorrow. Furthermore, therapeutic efficacy should not be neglected over concerns regarding drug interactions. Many patients are at risk of clinically relevant drug interactions involving antihypertensive drugs but, presently, even more patients may be at risk of suffering from the consequences of their inadequately treated hypertension. In this respect, the authors discuss controversial viewpoints on the overall clinical relevance of drug interactions occurring at the level of cytochrome P450 metabolism.

OBJECTIVES

Hyperhomocyst(e)inaemia is associated with endothelial dysfunction in animals and humans. Mechanisms responsible for endothelial dysfunction in hyperhomocyst(e)inaemia are poorly understood, but may involve impaired bioavailability of endothelium-derived nitric oxide (NO). We hypothesized that acute elevation of homocyst(e)ine by oral methionine loading may stimulate the formation of asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, due to a transmethylation reaction during the formation of homocyst(e)ine from methionine. We studied nine healthy human subjects (five males, four females) aged 29±2 years. Flow-mediated vasodilation (FMD) in the brachial artery (endothelium-dependent) and vasodilation induced by nitroglycerine (endothelium-independent) were measured with high-resolution ultrasound before and 8 h after oral methionine (100 mg/kg in cranberry juice) or placebo (cranberry juice), on separate days and in random order. Plasma homocyst(e)ine and ADMA concentrations were measured by specific HPLC methods. After a methionine bolus, elevation of homocyst(e)ine (28.4±3.5 µmol/l) was associated with an increased plasma concentration of ADMA (2.03±0.18 µmol/l) and reduced FMD (1.54±0.92%). Placebo had no effect on these parameters. There was a significant inverse linear relationship between ADMA concentration and FMD (r =-0.49; P < 0.05), which was stronger than the relationship between the homocyst(e)ine concentration and FMD (r =-0.36; not significant). We conclude that acute elevation of the homocyst(e)ine concentration impairs vascular endothelial function by a mechanism in which an elevated concentration of ADMA may be involved. This finding may have importance for understanding the mechanism(s) leading to homocyst(e)ine-associated vascular disease, and its potential treatment.

OBJECTIVES

Acute allograft rejection in patients after cardiac transplantation is associated with intense infiltration of inflammatory cells. It has been shown in animal studies that this inflammatory process is accompanied by an induction of nitric oxide synthase (NOS) enzyme within the grafted organ. We sought to test the hypothesis that acute rejection in cardiac transplanted patients is associated with an increased production of nitric oxide. The radical nitric oxide is unstable in blood and oxidized to nitrite and nitrate; nitrate is secreted by the kidneys. Therefore, nitric oxide production was indirectly assessed by measuring urinary nitrate excretion. During a period of 1 yr, 86 consecutive patients after cardiac transplantation underwent one or more right heart biopsies. (total 194) in order to assess for acute graft rejection. At the time of biopsies, urine was collected under sterile conditions. Urinary nitrate excretion was expressed as the ratio of nitrate to creatinine concentration in the urine (μmol/mmol). Urinary nitrate excretion was 99.7±9.2 (mean±SEM) for patients without evidence of rejection, and tended to increase for patients with moderate/severe rejection (128±15.1). In a subgroup of patients who underwent several biopsies and showed different degrees of rejection (7 patients, 48 biopsies), urinary nitrate excretion significantly increased by about 99% during episodes of acute rejection. It is concluded that urinary nitrate excretion appears to be elevated in a subgroup of cardiac transplanted patients during episodes of acute rejection. Results are consistent with the hypothesis that acute graft rejection stimulates the production/release of nitric oxide. Because of a large interand intraindividual variation in urinary nitrate excretion, this parameter appears not to be suitable for diagnosis of acute rejection in cardiac transplanted patients.

Abstract: We compared the effects of L-arginine (L-ARG), the precursor of endogenous NO, on platelet aggregation and thromboxane A2 formation in vivo and in vitro. Human platelet-rich plasma (PRP) was anticoagulated with citrate (which decreases extracellular Ca2+) or with recombinant hirudin (which does not affect extracellular Ca2+). Two groups of 10 healthy male volunteers received intravenous infusions of L-ARG (30 g or 6 g, 30 min) or placebo. Blood was collected immediately before and at the end of the infusions for aggregation by ADP or collagen. Infusion of L-ARG inhibited ADP-induced aggregation in PRP anticoagulated with citrate by 37.5 6.3% (P < 0.05). In PRP anticoagulated with hirudin, aggregation was inhibited by 33.6 16.0% (P < 0.05). L-ARG infusion also inhibited platelet TXB2 formation and slightly, but not significantly decreased the urinary excretion rate of 2,3-dinor-TXB2; cGMP concentrations in PRP were significantly elevated during L-arginine infusion. In vitro preincubation with L-ARG (10 μM–2.5 mM) inhibited platelet aggregation in PRP anticoagulated with r-hirudin, but not citrate. This effect was stereospecific for L-arginine, as D-arginine had no effect. It was dependent upon NO synthase activity, as indicated by increased cGMP levels in PRP. Moreover, both the NOS inhibitor L-NMMA and the inhibitor of soluble guanylyl cyclase ODQ antagonized the effects of L-ARG. Haemoglobin, an extracellular scavenger of NO, partly antagonized the antiplatelet effects of L-ARG. 8-Br-cyclic GMP and the exogenous NO donor linsidomine inhibited aggregation in PRP anticoagulated with citrate or r-hirudin. The inhibitory effects of L-ARG on platelet aggregation in vitro were paralleled by increased cyclic GMP levels; L-ARG also inhibited platelet TXB2 formation in PRP anticoagulated with r-hirudin, but not citrate. We conclude that the L-arginine/NO pathway is present in human platelets as a Ca2+-dependent anti-aggregatory pathway. In vivo the formation of NO from L-ARG by endothelial cells may contribute to the platelet-inhibitory effects of L-ARG. NO-releasing compounds like linsidomine inhibit platelet aggregation in vitro independent of extracellular Ca2+.

Dietary supplementation of L-arginine, the precursor of endogenous NO, has been shown to enhance endothelial function in the cholesterol-fed rabbits. However, the mechanism by which dietary L-arginine accomplishes these effects has been unclear. In the present study we have assessed the plasma concentrations of L-arginine and of asymmetrical dimethylarginine (ADMA), a known endogenous inhibitor of NO synthase, in cholesterol-fed rabbits with or without dietary supplementation of L-arginine. Urinary nitrate excretion rates were assessed as an index of endogenous NO formation. Plasma L-arginine levels were not different between control and cholesterol-fed rabbits, but they were elevated nearly threefold in rabbits fed cholesterol + L-arginine. Plasma ADMA concentration increased about two-fold in hyper-cholesterolemia, but was unaffected by dietary L-arginine. Thus, dietary L-arginine elevated the plasma L-arginine/ADMA ratio above the normal level, and partly restored urinary nitrate excretion, which was decreased by hypercholesterolemia. We conclude that elevation of the L-arginine/ADMA ratio may at least partly explain the restored NO formation by exogenous L-arginine in hypercholesterolemia.

1. Endothelium-derived nitric oxide (NO) contributes to the regulation of vascular tone and blood pressure. Infusion of l-arginine produces systemic vasodilatation via stimulation of endogenous NO formation. Vasodilatation is accompanied by an increase in peripheral arterial blood flow. However, it is not known whether capillary nutritive blood flow increases as well. The time course and dose-response pattern of this effect remain to be elucidated. 2. Two groups of ten patients with peripheral vascular disease (PVD) received an intravenous infusion of 8 g or 30 g of l-arginine over a period of 40 min. Blood pressure and heart rate were monitored non-invasively. Muscular blood flow (MBF) of the calf was determined at 0, 20, 40, 60, 80 min by positron emission tomography with H215O as flow tracer. Plasma l-arginine and cyclic GMP (cGMP) levels were determined at the same time points. 3. l-arginine induced a dose-related decrease in blood pressure during the infusion period. MBF and plasma cGMP levels during and after the infusion of 8 g of l-arginine did not change significantly. In the patients receiving 30 g of l-arginine, MBF was enhanced significantly from 1.56 ± 0.14 to 2.09 ± 0.21 ml min−1 100 ml−1 at 40 min and 2.23 ± 0.15 ml min−1 100 ml−1 after 80 min (+43.0%). The increase in MBF was paralleled by an increase in plasma cGMP from 4789.8 ± 392.2 nmol/l at baseline to 9223.2 ± 1233.6 nmol/l at 40 min. 4. We conclude that intravenous l-arginine enhances nutritive capillary MBF in patients with PVD via the NO—cGMP pathway in a dose-related manner. This effect might be therapeutically beneficial in patients with PVD.

The endothelium regulates vascular function by releasing the vasodilator autacoid nitric oxide (NO) and the vasoconstrictor peptide endothelin-1 (ET-1). Impaired activity of NO as well as excessive activity of ET-1 have been demonstrated in hypercholesterolemia and atherosclerosis. Because dietary L-arginine can restore NO function and improve abnormal endothelium-dependent relaxation in hypercholesterolemic rabbits, we examined the effects of dietary supplementation with L-arginine in cholesterol-fed rabbits on endothelium-dependent vascular relaxation and ET-1-induced vascular contraction, as well as the systemic synthesis of ET-1. Rabbits were initially fed a diet enriched with 1% cholesterol for 4 weeks, followed by 0.5% cholesterol alone or supplemented with 2% L-arginine in drinking water during the next 12 weeks. Cholesterol feeding impaired endothelium-dependent relaxation of rabbit aortic rings ex vivo and increased urinary immunoreactive ET-1 excretion, along with decreased urinary nitrate excretion, an index of NO production. L-Arginine partially restored endothelium-dependent relaxation in parallel to increased urinary nitrate excretion and decreased urinary immunoreactive ET-1 excretion. Selective inhibition of ET-A receptors with BQ123 partially restored endothelium-dependent relaxation in hypercholesterolemic rabbits but had no effect on arterial rings from rabbits supplemented with L-arginine or from control animals. The contractile vascular response of aortic rings to exogenous ET-1 was increased in rabbits fed a high-cholesterol diet; this enhanced contractility to ET-1 was completely reversed by L-arginine. These data suggest that L-arginine restores endothelial function and normalizes the synthesis and vasoconstrictor response to ET-1 in hypercholesterolemia.

Background. Administration of l-arginine improves nitric oxide (NO) formation and endothelium-dependent vasodilation in atherosclerotic patients.

1. One of the major problems in the clinical use of low dose aspirin for the prevention of vascular occlusion is that it takes about 3–5 days to become effective, a time too long for patients with unstable angina or coronary thrombolysis. Intravenous aspirin may be expected to exert a more rapid effect, but its influence on endothelial prostacyclin synthesis is uncertain. 2. In a single-blind, randomized, prospective study, we compared the effects of a single intravenous low dose (50 mg) or high dose (500 mg) of aspirin or placebo infused over a 60 min period on platelet aggregation, platelet thromboxane A2 production and whole-body prostanoid synthesis in 10 healthy male subjects by gas chromatography-tandem mass spectrometry. 3. Before the study, blood flow rates in the basilic and subclavian veins were determined by sonographic colour velocity imaging; the infusion rate for low dose aspirin was calculated to avoid biologically effective plasma levels of aspirin in the systemic circulation. 4. Platelet aggregation induced by 1 mmol/l arachidonic acid was similarly inhibited by >85% within 30 min after the start of the infusion of high dose or low dose aspirin, respectively, and remained suppressed for 24 h. Platelet thromboxane A2 release declined gradually after low dose aspirin, reaching a minimum of 93% inhibition after 60 min. High dose aspirin suppressed platelet thromboxane A2 release to below the detection limit after 10 min. 5. Urinary excretion of the major urinary metabolite of thromboxane A2 (2,3-dinor-thromboxane B2) was equally suppressed by both dosages of aspirin [no significant difference between high dose (−83.2%) and low dose (−67.4%)]. The urinary excretion of the major urinary metabolite of prostacyclin (2,3-dinor-6-keto-prostaglandin F1α) and of prostaglandin E2 was also markedly decreased, by 79.2% and 63.5%, respectively, by high dose aspirin, whereas low dose aspirin suppressed 2,3-dinor-6-keto-prostaglandin F1α excretion significantly less (−30.3%; P <0.02), and had no inhibitory effect at all on prostaglandin E2 excretion, indicating that after intravenous low dose aspirin no biologically active acetylsalicylate was present in the systemic circulation. 6. These data show that intravenous low dose aspirin can inhibit platelet aggregation and thromboxane B2 synthesis within less than 2 h while sparing systemic cyclo-oxygenase activity. Partial inhibition of prostacyclin formation seems to be an unavoidable consequence of effective inhibition of platelet cyclooxygenase by aspirin.

L‐Arginine, the substrate of nitric oxide (NO) synthases (NOSs), is found in the mammalian organism at concentrations by far exceeding KMvalues of these enzymes. Therefore, additional L‐arginine should not enhance NO formation. In vivo, however, increasing L‐arginine concentration in plasma has been shown repeatedly to increase NO production. This phenomenon has been named the L‐arginine paradox; it has found no satisfactory explanation so far. In the present work, evidence for the hypothesis that the endogenous NOS inhibitors methylarginines, asymmetric dimethylarginine being the most powerful (IC501.5 μM), are responsible for the L‐arginine paradox is presented.

Objective: Dilated cardiomyopathy is characterized by elevated arterial vascular resistance and impaired nitric oxide (NO)-dependent vasodilation. Insulin-like growth factor-I (IGF-I) has been shown to stimulate endothelial NO-synthase resulting in endothelium-dependent vasodilation. Growth hormone (GH) substitution therapy leads in GH-deficient patients to significant increases of IGF-I which may alter systemic vascular resistance by stimulating NO production. This study was designed to evaluate the effects of treatment with recombinant human growth hormone (GH) on NO production and NO-dependent vascular effects in patients with dilated cardiomyopathy. Methods: 50 patients with dilated cardiomyopathy were randomly assigned to double-blind treatment with 2 I.U. of GH or placebo for 3 months. Central hemodynamics were determined by Swan-Ganz catheter and cardiac output was obtained by the thermodilution method. Serum GH and IGF-I levels were measured and systemic NO production was determined from urinary nitrate and cyclic GMP excretion rates in 42 patients. Results: GH treatment caused in comparison to the placebo group a significant increase of IGF-I by 91 ng/ml (P=0.0001). Urinary excretion rates of nitrate and cyclic GMP increased also significantly by 38 μmol/mmol creatinine (P=0.027) and 65 nmol/mmol creatinine (P=0.003), respectively. The parallel increase of both marker molecules indicates increased systemic NO production during GH treatment. Conclusion: GH treatment induces a significant, but moderate increase of systemic NO production in patients with dilated cardiomyopathy. This effect may be mediated by IGF-I stimulating endothelial NO synthase.

Chronic oral administration of L-arginine (L-ARG) has been shown to enhance endothelial function in cholesterol (CHOL)-fed rabbits and to reduce atherogenesis. We investigated whether modulation of endogenous NO production (as assessed by urinary NO3-excretion) by L-ARG and the inhibitor of NO synthesis, L-NAME, affects vascular superoxide (O2-) production in hypercholesterolemic rabbits. Phorbol-myristate-acetate (PMA)-stimulated O2-production from isolated aortic rings was increased in rabbits given CHOL (+159±28%) or CHOL + L-NAME (+149±37%) as compared to controls (-22±7%), and endothelium-dependent relaxations by acetylcholine were diminished in both groups. In aortic rings from rabbits given CHOL + L-ARG, PMA-induced O2-production was restored to control levels (+14±17%; p&lt;0.05), and endothelium-dependent cholinergic relaxations were also partly restored. Urinary NO3-excretion decreased in all animals fed a CHOL-enriched diet (p&lt;0.01). As NO inactivated by O2-is also oxidized to NO3-, this indicates a decreased endothelial production of NO. NO3-excretion was further decreased by L-NAME (p&lt;0.05 vs. CHOL), and partly restored by L-ARG (p&lt;0.05). We conclude that both a decreased production of NO and an enhanced breakdown of NO by O2-contribute to the diminished biological activity of endothelial NO in hypercholesterolemia. L-ARG restores endothelial function by enhancing NO formation and by protecting NO from early breakdown by O2-.

The effects of submaximal exercise on systemic nitric oxide (NO) formation, as assessed by measuring the urinary excretion rates of NO-3and of cyclic GMP, were compared in 10 endurance-trained and 6 untrained male subjects. Urinary excretion rates of NO-3(by gas chromatography) and cyclic GMP (by radioimmunoassay) were assesse before and after a 30min exercise test dlt 60% of each subject's individual maximal work capacity in hourly intervals. Urinary NO-3excretion in untrained and trained subjects was comparable at rest (104±35 vs. 110 ± 19 μmol/mmol creatinine, p=n.s.). It more than doubled during exercise in both groups (to 236±88 μmol/mmol creatinine in untrained and to 252±39 μmol/mmol creatinine in trained subjects, each p&lt;0.01) and rapidly decreased to baseline within 2 hours after the test. Resting urinary cyclic GMP excretion was fourfold higher in the athletes than in the untrained subjects (21±5 vs. 6±1 nmol/mmol creatinine, p&lt;0.05). During exercise it increased about twofold in both groups (to 52±12 and 10±1 nmol/mmol creatinine, respectively, each p&lt;0.01), and returned to baseline after its end. There was a correlation between urinary cyclic GMP and NO-3excretion (p &lt; 0.05) in both groups. We conclude that acute submaximal exercise increases the formation of NO in man, as reflected by the increased urinary excretion of NO-3and cyclic GMP. This may contribute to the vasodilation during physical exercise, and at least partly explain the beneficial effects of physical training in patients with cardiovascular diseases.

Objectives: <$O_SCPLOW>L<$C_SCPLOW>-arginine exerts anti-atherosclerotic effects in hypercholesterolaemic rabbits via modulating endogenous NO production. We investigated whether <$O_SCPLOW>L<$C_SCPLOW>-arginine inhibits thromboxane formation in vivo and platelet aggregation ex vivo in this animal model. Methods: The urinary excretion rates of 2,3-dinor-6-keto-PGF₁ (major urinary metabolite of PGI₂) and 2,3-dinor-TXB₂ (major urinary metabolite of thromboxane A₂) were used as indicators of platelet–endothelial cell interactions in vivo. Rabbits were fed 1% cholesterol (Cholesterol group, N=8), 1% cholesterol plus 2,25% <$O_SCPLOW>L<$C_SCPLOW>-arginine (Cholesterol+<$O_SCPLOW>L<$C_SCPLOW>-arginine, N=8), or normal rabbit chow (Control, N=4) for 12 weeks. Urine samples were collected in weekly intervals. At the end of the study period platelet aggregation ex vivo and endothelium-dependent and -independent vascular function of isolated aortic rings in vitro was assessed. Results: Urinary 2,3-dinor-TXB₂ excretion significantly increased in the cholesterol group (p<0.05), and endogenous NO formation (measured as urinary nitrate excretion) decreased (p<0.05). Both parameters were significantly correlated with each other (R=0.48, p<0.01). <$O_SCPLOW>L<$C_SCPLOW>-arginine partly restored urinary nitrate excretion and significantly reduced TXA₂ production to values even below those in the control group (p<0.001). Urinary 2,3-dinor-6-keto-PGF₁ excretion increased in early hypercholesterolaemia and returned to control values in the second half of the study period. The early increase in urinary 2,3-dinor-6-keto-PGF₁ excretion was attenuated by <$O_SCPLOW>L<$C_SCPLOW>-arginine. Platelet aggregation was significantly enhanced in cholesterol-fed rabbits and attenuated by dietary <$O_SCPLOW>L<$C_SCPLOW>-arginine. <$O_SCPLOW>L<$C_SCPLOW>-arginine also improved the impaired endothelium-dependent relaxations to ADP, and normalized the vasoconstrictor effects of 5-HT in isolated aortic rings. Conclusions: Cholesterol-feeding enhances platelet aggregation and TXA₂ formation, and stimulates platelet–endothelial cell interaction in rabbits. These effects are probably due to impaired NO elaboration, as indicated by decreased urinary nitrate excretion. Chronic dietary supplementation with <$O_SCPLOW>L<$C_SCPLOW>-arginine elevates systemic NO elaboration and significantly increases the PGI₂/TXA₂ ratio. It thus beneficially influences the homeostasis between vasodilator and vasoconstrictor prostanoids in vivo.

Objective: The effects of long term oral administration of L-arginine, NG-nitro-L-arginine methyl-ester (L-NAME), or molsidomine v placebo on blood pressure and the urinary excretion rates of NO₃– and cyclic GMP were studied in Munich Wistar Frömter (MWF) rats. Methods: L-arginine (2 g·kg–1 body weight, n = 8), NG-nitro-L-arginine methylester (L-NAME; 5 mg·kg–1, n = 8), or molsidomine (3 mg·kg–1, n = 8) were given in drinking water and compared with placebo (n = 8) over a period of five months. Urinary excretion rates of NO₃– (by gas chromatography) and cyclic GMP (by radioimmunoassay) were assessed in monthly intervals, as well as systolic blood pressure (tail plethysmography). Results: Mean basal blood pressure was 143.5(SEM 2.2) mm Hg. It was unaffected by L-arginine or molsidomine, but continuously and significantly increased during L-NAME treatment to 199.3(6.4) mm Hg (p<0.05). Urinary excretion of NO₃– increased by 20-41% v controls in L-arginine and molsidomine treated rats (p<0.05), and decreased by 5-15% in L-NAME treated rats (p<0.05). Urinary excretion of cyclic GMP increased by 9-38% v controls in the L-arginine and molsidomine treated groups and decreased by 5-20% in the L-NAME treated animals. Consistent with their higher blood pressure, L-NAME treated animals displayed cardiac hypertrophy. Conclusions: Determination of urinary NO₃– excretion by gas chromatography is a sensitive and specific method to assess NO formation in vivo. Long term oral administration of L-arginine in MWF rats increases NO production (as assessed by the urinary excretion rates of NOf and cyclic GMP), but does not significantly influence systolic bood pressure, whereas L-NAME induces sustained hypertension and cardiac hypertrophy due to inhibition of NO formation. Cardiovascular Research 1994;28:494-499