Plasma Levels Of Nitric Oxide Metabolites Research Articles

Iron nitrosyl complexes are formed from nitrite in the human placenta

Placental nitric oxide (NO) is critical for maintaining perfusion in the maternal-fetal-placental circulation during normal pregnancy. NO and its many metabolites are also increased in pregnancies complicated by maternal inflammation such as preeclampsia, fetal growth restriction, gestational diabetes, and bacterial infection. However, it is unclear how increased levels of NO or its metabolites affect placental function or how the placenta deals with excessive levels of NO or its metabolites. Since there is uncertainty over the direction of change in plasma levels of NO metabolites in preeclampsia, we measured the levels of these metabolites at the placental tissue level. We found that NO metabolites are increased in placentas from patients with preeclampsia compared to healthy controls. We also discovered by ozone-based chemiluminescence and electron paramagnetic resonance that nitrite is efficiently converted into iron nitrosyl complexes (FeNOs) within the human placenta and also observed the existence of endogenous FeNOs within placentas from sheep and rats. We show these nitrite-derived FeNOs are relatively short-lived, predominantly protein-bound, heme-FeNOs. The efficient formation of FeNOs from nitrite in the human placenta hints toward the importance of both nitrite and FeNOs in placental physiology or pathology. As iron nitrosylation is an important posttranslational modification that affects the activity of multiple iron-containing proteins such as those in the electron transport chain, or those involved in epigenetic regulation, we conclude that FeNOs merit increased study in pregnancy complications.

Effect of NOS Inhibitors and Anticoagulants on Nitric Oxide Production in a Tissue-factor Induced Rat DIC Model.

We examined the mechanism of nitric oxide (NO) production in a tissue-factor (TF)-induced disseminated intravascular coagulation (DIC) model in rats, using inducible nitric oxide synthase (iNOS) inhibitor (L-NIL), endothelial nitric oxide synthase (eNOS) inhibitor (L-NAME), Factor Xa inhibitor (DX-9065a), and thrombin inhibitor argatroban. Experimental DIC was induced by sustained infusion of 3.75 U/kg TF for 4 h via the tail vein. We then investigated the effect of these four agents on TF-induced DIC. Administration of L-NIL or L-NAME during induction of TF-induced DIC did not affect hemostatic markers, whereas elevated plasma levels of NO metabolites (NOX) were significantly suppressed by co-administration of L-NAME. A significant increase in eNOS-mRNA expression was observed in the TF-induced DIC model. Argatroban almost completely suppressed eNOS-mRNA expression. eNOS plays an important role in the NO production in the TF-induced DIC, and thrombin is a key stimulant of eNOS-mRNA expression in this model.

Syzygium gratum Extract Alleviates Vascular Alterations in Hypertensive Rats.

Background and Objectives: Syzygium gratum (SG) is a local vegetable and widely consumed in Thailand. Previously, a strong antioxidative effect of SG extract has been reported. The effects of SG extract on hypertension have remained unknown. The effect of SG aqueous extract on blood pressure and vascular changes were examined in L-NAME-induced hypertensive rats (LHR), and its potential active constituents were also explored. Materials and Methods: Male Sprague Dawley rats were allocated to control, L-NAME (40 mg/kg/day), L-NAME + SG (100, 300, 500 mg/kg/day), or captopril (5 mg/kg/day) groups. The components of SG extract were analyzed. Results: The analysis of aqueous SG extract was carried out using HPLC-Mass spectroscopy, and phenolic compounds could be identified as predominant components which might be responsible for its antihypertensive effects observed in the LHR model (p < 0.05). Additionally, SG extract also improved vascular responses to acetylcholine and decreased vascular remodeling in LHR (p < 0.05). Enhancements of eNOS expression and plasma nitric oxide metabolite levels, and attenuation of angiotensin converting enzyme (ACE) activity and plasma angiotensin II levels were observed in the LHR group treated with SG. Moreover, SG exhibited strong antioxidant activities by reducing vascular superoxide generation and systemic malondialdehyde in LHRs. Captopril suppressed high blood pressure and alleviated vascular changes and ACE activity in LHRs, similar to those of the SG extract (p < 0.05). Conclusion: Our results suggest that the SG extract exhibited antihypertensive effects, which is relevant to alleviation of vascular dysfunction and vascular remodeling of LHRs. These effects might be mediated by phenolic compounds to inhibit ACE activity and scavenge reactive oxygen species in LHR.

Carthamus tinctorius L. extract improves hemodynamic and vascular alterations in a rat model of renovascular hypertension through Ang II-AT1R-NADPH oxidase pathway

Carthamus tinctorius L. (CT) is widely used in Asian countries as a beverage and in folk medicine. The effects of CT extract on hemodynamics, vascular remodeling, the renin-angiotensin system (RAS) and oxidative stress in the two-kidney, one clip (2K-1C) hypertensive rat model were investigated. Renovascular hypertension was induced in male Sprague-Dawley rats and were treated with CT extract (500mg/kg/day) or captopril (5mg/kg/day) or vehicle for four weeks. CT extract or captopril reduced blood pressure, hindlimb vascular resistance, and increased hindlimb blood flow in 2K-1C hypertensive rats (p<0.05). Increases in aortic wall thickness, cross-sectional area and collagen deposition in 2K-1C rats were alleviated with CT extract or captopril treatment (p<0.05). CT extract or captopril suppressed RAS activation, including elevated serum ACE activity, and plasma Ang II level and up-regulated aortic AT1R protein expression in 2K-1C rats (p<0.05). Furthermore, CT extract or captopril reduced vascular superoxide production, aortic NADPH oxidase subunit gp91phox expression and increased plasma nitric oxide metabolite levels in 2K-1C rats (p<0.05). These findings suggest that CT extract ameliorated hemodynamic alteration and vascular remodeling in 2K-1C hypertensive rats. Possible mechanisms may involve RAS inhibitor effects and potent antioxidant activity.

Nitric oxide mediates effects of acute, not chronic, naltrexone on LPS-induced hepatic encephalopathy in cirrhotic rats.

Recent studies suggest endogenous opioids and nitric oxide (NO) are involved in the pathophysiology of hepatic encephalopathy (HE). In this study, the interaction between the opioid receptor antagonist and NO was investigated on lipopolysaccharide (LPS)-induced HE in cirrhotic rats. Male rats were divided in the sham- and bile duct ligation (BDL)-operated groups. Animals were treated with saline; naltrexone (10 mg/kg, i.p.); or L-NAME (3 mg/kg, i.p.), alone or in combination with naltrexone. To induce HE, LPS (1 mg/kg, i.p.) was injected 1 h after the final drug treatment. HE scoring, hepatic histology, and plasma NO metabolites levels and mortality rate were recorded. Deteriorated level of consciousness and mortality after LPS administration significantly ameliorated following both acute and chronic treatment with naltrexone in cirrhotic rats. However, acute and chronic administration of L-NAME did not change HE scores in cirrhotic rats. The effects of acute but not chronic treatment of naltrexone on HE parameters were reversed by L-NAME. Plasma NOx concentrations elevated in BDL rats, which were decreased after acute and chronic treatment by naltrexone or L-NAME, significantly. We suggest both acute and chronic treatment with naltrexone improved LPS-induced HE. But, only acute treatment with naltrexone may affect through NO pathway.

Elevated circulating endothelial cell-derived microparticle levels in patients with liver cirrhosis: a preliminary report.

Aim of the studyTo determine plausible associations between liver cirrhosis and circulating endothelial cell-derived microparticles (EMPs), vascular endothelial growth factor (VEGF) levels and plasma nitric oxide (NO) metabolites.Material and methodsSixty patients with cirrhosis and 20 healthy control subjects were enrolled in the study. Circulating EMPs from platelet-poor plasma samples were examined by flow cytometry. These microparticles were categorized into endothelial cell-derived activated MPs (EMP-ac) (CD31+ CD42b– AN-V–) and endothelial cell-derived apoptotic MPs (EMP-ap) (CD31+ CD42b– AN-V+). Plasma VEGF levels were measured by enzyme-linked immunosorbent assay. Plasma NO metabolites (NOx–) levels were determined using a Greiss reaction method.ResultsCompared with the healthy control subjects, the patients with cirrhosis showed a significant increase in plasma levels of both phenotypes of EMPs. When the presence of ascites was considered, the plasma levels of EMP-ap were higher (p < 0.01), as well as NOx– (p < 0.05). EMP-ap positively correlated with VEGF level in all cirrhotic patients and this correlation was stronger in decompensated cirrhotic patients. In multivariate logistic regression analysis, the independent factors associated with the presence of ascites were high EMP-ap levels and elevated VEGF levels.ConclusionsElevated plasma levels of EMP-ap in addition to high levels of VEGF might be considered as valuable parameters for predicting the occurrence of ascites in cirrhotic patients.

Role of T Regulatory Lymphocytes in the Pathogenesis of High-Fructose Diet–Induced Metabolic Syndrome

We recently showed that T regulatory lymphocytes (Treg), which are immune suppressors of inflammatory responses, play a role blunting the development of hypertension-induced injury. Treg are unchanged or decreased in children with metabolic syndrome, and therefore, their role in metabolic syndrome remains unclear. We hypothesized that Treg number or function would be depressed in a high-fructose diet-induced metabolic syndrome-like model in rats. Sprague-Dawley rats were fed normal chow or a high-fructose diet for 5 weeks. The high-fructose diet-induced a 3.8-fold increase in plasma triglycerides and a 14% reduction in high-density lipoprotein cholesterol (P<0.001). The high-fructose diet increased reactive oxygen species in aorta and periaortic adipose tissue 2.8-fold (P<0.05), and reduced nicotinamide adenine dinucleotide phosphate oxidase activity 1.9-fold in aorta, and 2.5-fold in the heart (P<0.05). It also increased plasma nitric oxide metabolite levels 6.4-fold (P<0.001). Western blots showed that the high-fructose diet increased ≥2.3-fold vascular and in platelet endothelial cell adhesion molecule 1 in aorta (P<0.01). It did not affect monocyte/macrophage aortic infiltration but caused a 2.4-fold increase in collagen deposition in the aortic media (P<0.01). No change in plasma interleukin-10 was detected. The percentage of spleen CD4+ CD25- and Treg (CD4+ CD25(high)) cells was unaltered by the high-fructose diet. However, cultured Treg from high-fructose diet-fed rats secreted 62% less interleukin-10 than control cells (P<0.05), suggesting a decreased Treg function, which could play a role in the development of cardiovascular complications of the metabolic syndrome.

Protective Effect of Fetal Hemoglobin On Inflammation-Induced Expression of Hypoxia-Inducible Factor-1α (HIF-1α) in Sickle Mice: Microvascular Implications

AbstractAbstract 3250Chronic inflammation is a salient feature of human sickle cell disease (SCD) and transgenic-knockout sickle (BERK) mouse model. Although tissue ischemia is the primary instigator of hypoxia-inducible factor (HIF) activation, a number of inflammatory factors/pathways and oxidative stress can potentially induce expression of HIF-1α. Increased oxidative stress and inflammation are implicated in the activation of HIF-1α under normoxic conditions. HIF can trigger transcription of genes for vasoactive molecules such as vascular endothelial growth factor (VEGF), heme oxygenase-1 (HO-1) and endothelin, which are implicated in the pathophysiology of SCD. We hypothesize that, in SCD, inflammation coupled with nitric oxide (NO) depletion will induce expression of HIF-1α. To this end, we have examined the expression of HIF-1α in normoxic BERK mice expressing exclusively human α- and βS- globins, and evaluated the effect of HbF in BERK mice (i.e., <1.0%, 20% and 40% HbF). We have previously shown that HbF exerts anti-sickling and anti-inflammatory effects (Kaul et al. J Clin Invest, 2004; Dasgupta et al. Am J Physiol, 2010). Here, we show that HIF-1α is expressed in BERK mice under normoxic conditions (i.e., normal hemoglobin oxygen saturation levels). In BERK mice expressing HbF, HIF-1α expression decreased concomitantly with increasing HbF, commensurately with increased NO bioavailability, and showed a strong inverse correlation with plasma NO metabolites (NOx) levels. Reduced HIF-1α expression in BERK mice expressing HbF was associated with decreased HO-1 and VEGF expression, and reduced serum endothelin-1 (ET-1) levels, which are among the target vasoactive molecules of HIF-1α. Furthermore, the commensurate decrease in HIF-1α expression with increase in HbF levels in BERK mice was accompanied by a distinct decrease in soluble (s) forms of endothelial activation markers such as sP-selectin and vascular cell adhesion molecule-1 (sVCAM-1). Notably, arteriolar dilation, enhanced volumetric blood flow and low blood pressure in normoxic BERK mice all showed a trend toward normalization with the introduction of HbF. Also, arginine treatment reduced HIF-1α expression as well as ET-1 levels in normoxic BERK mice, supporting a role of decreased NO bioavailability in HIF-1α activation. The present in vivo studies show that reduced inflammation and increased NO production in normoxic BERK mice (expressing HbF or treated with arginine) are distinctly associated with suppression of HIF-1α activation and inhibition of vasodilators, resulting in improved microvascular and hemodynamic parameters in the BERK model of sickle cell disease. The unique feature of inflammation in SCD is that it can be ameliorated by increased HbF, thereby coupling HbS polymerization/sickling to NO depletion, HIF-1α expression and inflammation in this disease. Disclosures:No relevant conflicts of interest to declare.

Antisickling fetal hemoglobin reduces hypoxia-inducible factor-1α expression in normoxic sickle mice: microvascular implications

Chronic inflammation is a salient feature of sickle cell disease (SCD) and transgenic-knockout sickle (BERK) mice. Inflammation is implicated in the activation of hypoxia-inducible factor-1α (HIF-1α) under normoxic conditions. We hypothesize that, in SCD, inflammation coupled with nitric oxide (NO) depletion will induce expression of HIF-1α, a transcription factor with wide-ranging effects including activation of genes for vasoactive molecules. To this end, we have examined the expression of HIF-1α in normoxic BERK mice expressing exclusively human α- and β(S)- globins, and evaluated the effect of fetal hemoglobin (HbF) in BERK mice (i.e., <1.0%, 20%, and 40% HbF). HbF exerts antisickling and anti-inflammatory effects. Here, we show that HIF-1α is expressed in BERK mice under normoxic conditions, accompanied by increased expression of its vasoactive biomarkers such as VEGF, heme oxygenase-1 (HO-1), and serum ET-1 levels. In BERK mice expressing HbF, HIF-1α expression decreases concomitantly with increasing HbF, commensurately with increased NO bioavailability, and shows a strong inverse correlation with plasma NO metabolites (NOx) levels. Reduced HIF-1α expression is associated with decreased HO-1, VEGF, and ET-1. Notably, arteriolar dilation, enhanced volumetric blood flow, and low blood pressure in normoxic BERK mice all show a trend toward normalization with the introduction of HbF. Also, arginine treatment reduced HIF-1α, as well as VEGF expression in normoxic BERK mice, supporting a role of NO bioavailability in HIF-1α activation. Thus HIF-1α expression in normoxic sickle mice is likely a consequence of chronic inflammation, and HbF exerts an ameliorating effect by decreasing sickling, increasing NO bioavailability, and reducing inflammation.

Inducible nitric oxide synthase plays important roles in allergic reactions of pollinosis in mice sensitized with pollen allergy

To elucidate the possible involvement of nitric oxide (NO) derived from inducible NO-synthase (iNOS) in the pathogenesis of patients with allergic rhinitis, we analyzed changes in the frequency of sneezing, plasma levels of NO metabolites, α-melanocyte-stimulating hormone (MSH) and immunoglobulin E and tracheal expression of IgA and mast cell tryptase in control and iNOS−/− mice. Eight-week-old control and iNOS−/− male C57BL/6j mice were sensitized with Cry j I antigen. After the last intranasal challenge of antigen, changes in the frequency of sneezing and plasma levels of IgE, α-MSH and NO metabolites and tracheal expression of iNOS, IgA and mast cell tryptase were analyzed by ELISA and immunohistochemistry using specific antibodies. The sensitization of mice with Cry j I antigen increased plasma levels of NO metabolites, α-MSH and IgE and tracheal expression of iNOS, IgA and mast cell tryptase in control not but in iNOS−/− mice. Administration of NG-nitro-L-arginine methyl ester strongly inhibited all these changes occurred in control mice. These results indicate that the symptom of pollinosis including sneezing is enhanced by iNOS derived NO through activation of α-MSH-receptor containing mast cells enriched with tryptase.

Quercetin restores plasma nitrite and nitroso species levels in renovascular hypertension

Quercetin has antioxidants properties which may increase nitric oxide (NO) bioavailability. However, the effects of quercetin on NO status have been poorly studied. We evaluated whether quercetin improves the plasma levels of NO metabolites in two-kidney one-clip (2K1C) hypertensive rats and assessed its effect on endothelial function. Sham-operated and 2K1C rats were treated with quercetin (10mg(-1) kg(-1) day(-1) by gavage) or vehicle for 3weeks. Systolic blood pressure (SBP) was monitored weekly. Vascular responses to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in hindquarter vascular bed. Plasma nitrate levels were assessed by Griess reagent and plasma nitrite and nitroso species (S, N-nitroso species) were assessed by ozone- based chemiluminescence. Aortic NADPH oxidase activity and superoxide production were evaluated. While quercetin had no effects in control normotensive rats (P > 0.05), it significantly reduced SBP in 2K1C rats (P < 0.05). At the end of treatment, plasma nitrate levels were similar in all experimental groups (P > 0.05). However, plasma nitrite and the nitroso species levels were significantly lower in 2K1C rats when compared with controls (P < 0.05). Quercetin treatment restored plasma nitrite and nitroso species levels to those found in the sham-vehicle group (P < 0.05). While quercetin treatment induced no significant changes in responses to SNP (P > 0.05), it restored the vascular responses to Ach. Quercetin significantly attenuated 2K1C-hypertension-induced increases in NADPH oxidase activity and vascular superoxide production (P < 0.05). These results suggest that the antihypertensive effects of quercetin were associated with increased NO formation and improved endothelial function, which probably result from its antioxidant effects.

Association between plasma nitric oxide metabolites levels and negative symptoms of schizophrenia: a pilot study

Nitric oxide (NO) is involved in pathophysiology of psychiatric disorders such as depression and schizophrenia. We hypothesize that plasma levels of NO and its metabolites (NO(x)) are decreased in patients with schizophrenia. To examine the hypothesis, we compared plasma NO(x) levels between 30 schizophrenic patients (M/F: 18/12, age: 38 +/- 15 years) and age- and sex-matched 30 healthy controls (M/F: 18/12, age: 41 +/- 19 years), and we also examined the effects of risperidone on plasma NO(x) levels in schizophrenic patients. The baseline plasma NO(x) levels were significantly lower in the schizophrenia group (1.85 +/- 0.70 microM) than those in control group (3.37 +/- 2.27 microM). A significantly negative correlation was found between plasma NO(x) levels and PANSS-N scores before risperidone administration (rho = -0.385, p = 0.0416). Treatment with risperidone significantly increased the plasma NO(x) levels by 8 weeks (before; 1.85 +/- 0.70 microM, after; 2.25 +/- 1.00 microM, p = 0.0491). These results suggest that NO might be one of the candidates factors which are associated with the pathophysiology of negative symptoms of schizophrenia.

Nitric oxide contributes to learning and memory deficits observed in hypothyroid rats during neonatal and juvenile growth

INTRODUCTION:Severe cognitive impairment follows thyroid hormone deficiency during the neonatal period. The role of nitric oxide (NO) in learning and memory has been widely investigated.METHODS:This study aimed to investigate the effect of hypothyroidism during neonatal and juvenile periods on NO metabolites in the hippocampi of rats and on learning and memory. Animals were divided into two groups and treated for 60 days from the first day of lactation. The control group received regular water, whereas animals in a separate group were given water supplemented with 0.03% methimazole to induce hypothyroidism. Male offspring were selected and tested in the Morris water maze. Samples of blood were collected to measure the metabolites of NO, NO2, NO3 and thyroxine. The animals were then sacrificed, and their hippocampi were removed to measure the tissue concentrations of NO2 and NO3.DISCUSSION:Compared to the control group's offspring, serum thyroxine levels in the methimazole group's offspring were significantly lower (P<0.01). In addition, the swim distance and time latency were significantly higher in the methimazole group (P<0.001), and the time spent by this group in the target quadrant (Q1) during the probe trial was significantly lower (P<0.001). There was no significant difference in the plasma levels of NO metabolites between the two groups; however, significantly higher NO metabolite levels in the hippocampi of the methimazole group were observed compared to controls (P<0.05).CONCLUSION:These results suggest that the increased NO level in the hippocampus may play a role in the learning and memory deficits observed in childhood hypothyroidism; however, the precise underlying mechanism(s) remains to be elucidated.

Behaviour of nitric oxide metabolites in unprofessional athletes before and after a cardiopulmonary test

Physical training causes an increase in nitric oxide (NO) production [2, 3, 8, 9] and this datum explains the link between exercise and endothelium and seems to demonstrate how regular training upregulates eNOS expression, although it is not sure if this upregulation is due to shear stress or metabolic factors [3]. However, it must be underlined that besides to be directly influenced by exogenous NO, erythrocytes express a functional NOS [5, 6, 11, 13] that raises the circulation NO pool. The literature data describe that an 8-week exercise training induced an increase in plasma levels of NO metabolites (NOx), that persisted four weeks after interruption of training [8]. A similar trend was also found after a 12-week physical training [9]. Other authors noted instead that at baseline the NOx level was higher in sedentary young subjects compared to the older ones while this difference was not present between younger and older athletes; this difference was eliminated in sedentary subjects by physical training [2]. Now we evaluated the NOx level before and after a cardio-pulmonary test in unprofessional athletes who practised different kinds of sports, in comparison with sedentary controls (SC).

Liposome-Encapsulated Hemoglobin Transfusion Rescues Rats Undergoing Progressive Hemodilution From Lethal Organ Hypoxia Without Scavenging Nitric Oxide

To investigate the efficacy of liposome-encapsulated hemoglobin (LHb) transfusion in rats undergoing lethal progressive hemodilution. Unlike other acellular hemoglobin-based oxygen carriers, LHb has lipid bilayer membranes that are similar to mammalian red blood cells (RBCs), which prevent hemoglobin from having any direct contact with the blood components and the endothelium. Acellular hemoglobin has a high affinity for nitric oxide (NO), and because they are reported to behave as NO scavengers, acellular hemoglobin-based oxygen carriers could have pressor effects on the peripheral vessels. During a massive hemorrhage, acellular hemoglobin caused vasoconstriction could decrease peripheral perfusion, thereby leading to diminished oxygen delivery. Rats were subjected to blood withdrawal (0.2 mL/min) with a simultaneous resuscitation using an isovolemic fluid transfusion that contained LHb, 5% albumin, or washed rat RBCs for 150 minutes (n = 15 in each group). All rats transfused with LHb or RBCs were rescued from lethal progressive hemodilution, whereas none of the albumin-transfused rats survived. LHb did not affect the plasma NO metabolite levels, suggesting it was not a potent NO scavenger. LHb also improved hemodilution-induced metabolic acidosis, and reduced exaggerated neuroendocrine responses and injuries to the heart, liver, and kidney. It suppressed expression of hypoxia-inducible factor-1alpha in the liver and kidney, suggesting improvement of hypoxia at molecular response levels. However, neither transfused LHb nor RBCs improved the acute lung injury that occurs after progressive hemodilution. LHb transfusion is effective in rescuing rats undergoing progressive hemodilution from lethal organ hypoxia without scavenging NO.

Electron paramagnetic resonance investigation on modulatory effect of benidipine on membrane fluidity of erythrocytes in essential hypertension

It has been shown that benidipine, a long-lasting calcium (Ca) channel blocker, may exert its protective effect against vascular disorders by increasing nitric oxide (NO) production. The purpose of the present study was to investigate whether orally administered benidipine might influence the membrane function in patients with essential hypertension. We measured the membrane fluidity of erythrocytes by using an electron paramagnetic resonance (EPR) and spin-labeling method. In the preliminary study using erythrocytes obtained from healthy volunteers, benidipine decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-NS in the EPR spectra in vitro. The finding indicated that benidipine increased the membrane fluidity and improved the microviscosity of erythrocytes. In addition, it was demonstrated that the effect of benidipine on membrane fluidity of erythrocytes was significantly potentiated by the NO-substrate, L-arginine. In the separate series of the study, we observed that orally administered benidipine for 4 weeks significantly increased the membrane fluidity of erythrocytes with a concomitant increase in plasma NO metabolite levels in hypertensive subjects. The results of the present study demonstrated that benidipine might increase the membrane fluidity and improve the microviscosity of erythrocytes both in vitro and in vivo, to some extent, by the NO-dependent mechanism. Furthermore, it is strongly suggested that orally administered benidipine might have a beneficial effect on the rheologic behavior of erythrocytes and the improvement of the microcirculation in hypertensive subjects.

Copper deficient rats exhibit no alterations in plasma or brain NO metabolites, 3‐nitrotyrosine peptide abundance, or NOS mRNA expression

Others have reported that copper deficient (Cu−) rodents have alterations in nitric oxide (NO) biology including: higher nitric oxide synthase (NOS) activity and expression, and higher 3‐nitrotyrosine abundance (a marker of peroxynitrite production predicted to be higher because of higher NO and superoxide). Altered NO could impact brain development and metabolism. Holtzman rat dams were fed a Cu− diet and given either Cu supplemented (Cu+) or deionized water starting on gestation day 7. Cu− dams at weaning and their male pups at P26 had near zero plasma ceruloplasmin activity. Compared to Cu+ P26 male rats Cu− rats had heart/body weight values more than twice as high. However, plasma levels of NO metabolites (nitrite and nitrate) were not altered by Cu deficiency in dams or pups. Mean values in all groups were approximately 60 μM. Cerebellar extracts of P24 Cu− and Cu+ rats contained equivalent NO metabolite levels; furthermore, a 30kD 3‐nitrotyrosine containing peptide was detected in equal amounts in P24 Cu− and Cu+ cerebellar extracts. However, levels of CCS were markedly higher and CCO subunit IV nearly absent in Cu− lanes confirming severe Cu deficiency. Abundance of brain nNOS and eNOS mRNA, detected by real time qPCR, was not different between Cu− and Cu+ rat pups. We conclude perturbation in NO biology is unlikely to impact the altered development and metabolism of Cu− rat brain.Supported in part by NIH HD‐39708.

ADIPONECTIN AND NITRIC OXIDE PRODUCTION IN NORMOTENSIVE AND HYPERTENSIVE MEN

SUMMARY 1 In the present study, we examined the possible relationship between circulating adiponectin and plasma levels of nitric oxide (NO) metabolites (nitrite and nitrate) in normotensive and hypertensive men. 2 The concentration of circulating adiponectin was significantly lower in hypertensive men compared with normotensive men. Plasma levels of NO metabolites were also reduced in hypertensive men compared with normotensive men. 3 Circulating adiponectin was significantly correlated with plasma levels of NO metabolites (nitrite and nitrate) in the overall analysis of normotensive and hypertensive men (r = 0.377; n = 52; P < 0.01). When analysis of the correlation for normotensive and hypertensive men was performed separately, there was a significant correlation between circulating adiponectin and plasma levels of NO metabolites in normotensive men, but not in hypertensive men. 4 The results of the present study are consistent with the hypothesis that adiponectin-mediated production of NO may be altered in hypertensive men.

HYPERHOMOCYSTEINAEMIA AND MEMBRANE FLUIDITY OF RED BLOOD CELLS IN NORMOTENSIVE AND HYPERTENSIVE MEN: AN ELECTRON PARAMAGNETIC RESONANCE INVESTIGATION

SUMMARY 1 The purpose of the present study was to assess the possible link between plasma homocysteine and membrane fluidity in normotensive and hypertensive men. 2 The membrane fluidity (a reciprocal value of membrane microviscosity) of red blood cells (RBC) was measured using an electron paramagnetic resonance and spin-labelling method. The membrane fluidity of RBC was decreased in hypertensive compared with normotensive men. 3 Total plasma homocysteine levels were significantly higher in hypertensive men than normotensive men. In contrast, plasma levels of nitric oxide (NO) metabolites were significantly lower in hypertensive men than in normotensive men. The decreased membrane fluidity of RBC was associated with hyperhomocysteinaemia and reduced plasma levels of NO metabolites. 4 The results of the present study suggest that hyperhomocysteinaemia may have a role in modulating the rheological behaviour of RBC and microcirculation in men by, at least in part, reducing NO bioavailability.

Adiponectin and Membrane Fluidity of Erythrocytes in Normotensive and Hypertensive Men

Abnormalities in physicochemical properties of the cell membranes may underlie the defects that are strongly linked to hypertension. Recent evidence indicates that adiponectin may have protective effects against cardiovascular diseases. The purpose of the present study was to assess the possible link between plasma adiponectin and membrane fluidity in normotensive (NT) and hypertensive (HT) men. We measured the membrane fluidity (a reciprocal value of membrane microviscosity) of erythrocytes in NT and HT men by using an electron paramagnetic resonance and spin-labeling method. The order parameter (S) for the spin label agent (5-nitroxide stearate) and the peak height ratio (h0/h(-1)) for 16-nitroxide stearate in the electron paramagnetic resonance spectra of erythrocytes were significantly higher in HT men than in NT men, indicating that membrane fluidity of erythrocytes was decreased in HT men compared with NT men. Both of plasma adiponectin and nitric oxide (NO) metabolite levels were significantly lower in HT men than in NT men. The plasma adiponectin levels were correlated with plasma NO metabolites. The S and the h0/h(-1) of erythrocytes were inversely correlated with the plasma adiponectin and NO metabolite levels, indicating that the decreased membrane fluidity of erythrocytes was associated with hypoadiponectinemia and reduced plasma NO metabolites. The results of the present study demonstrated that plasma adiponectin levels were lower in HT men than in NT men and that hypoadiponectinemia was associated with decreased membrane fluidity of erythrocytes. The finding suggests that adiponectin may be linked to the rheologic behavior of the erythrocytes and the microcirculation in men, at least in part, by the NO-dependent mechanism.