Nitric Oxide Production In Rats Research Articles

Content of nitric oxide and copper in the olfactory bulbs of the rats brain after modeling of cerebral stroke and intranasal administration of mesenchymal stem cells

Introduction. With a decrease in the oxygen content in the inhaled air, violations of the cerebral blood flow, brain ischemia occurs, which can end in an ischemic stroke. Aim. Comparative analysis of the intensity of nitric oxide (NO) production and the copper content in the olfactory bulb tissues of the brain of male Wistar rats after modeling an ischemic stroke. Materials and methods. Modeling of ischemic stroke by ligation at the bifurcation level of both common carotid arteries and measuring the content of NO and copper by EPR spectroscopy. Results. The relative changes in the number of NO-containing complexes and the copper content were estimated from the integrated signal intensity of the complexes (DETC)2-Fe2+-NO and (DETC)2- Cu. A significant decrease by 47 % after 1 and 57 % after 2 days, respectively, in the NO content in the olfactory bulb of the rat brain was found after the ischemia modeling. The level of NO production in rats that underwent ischemia simulation with simultaneous intranasal administration of mesenchymal stem cells (MSCs) was also reduced by 51 % after 1 and 70 % after 2 days, respectively, after ischemia modeling. There was no significant difference in the NO content in the rats after ischemia modeling with simultaneous intranasal administration of MSCs compared to the ischemic rats. The copper content, which corresponds to the level of superoxide dismutase 1 and 3, in the rat’s olfactory bulb tended to increase after ischemia modeling and it persisted for two days of observation (an increase of 50 % in both cases). Intranasal administration of MSCs was accompanied by a significant increase in the Cu content (by 89 %) 1 day after the ischemia modeling, and 2 days later – by a decrease in its content by 36 % (compared to the control). In the control animals that were not subjected to surgical operations, no changes in the content of NO or copper were observed. Conclusion. The experiments showed a 2-fold decrease in the NO content in the olfactory bulb of the rat brain 1 and 2 days after the ischemia modeling, and demonstrated that the intranasal administration of MSCs did not affect the intensity of NO production on the 1st and 2nd days after the brain ischemia modeling, but was accompanied by an increase in the antioxidant protection of the nervous tissue one day after ischemia.

Angiotensin-(1\u20137) treatment blocks lipopolysaccharide-induced organ damage, platelet dysfunction, and IL-6 and nitric oxide production in rats

Sepsis can lead to shock, multiple organ failure, and even death. Platelets play an active role in the pathogenesis of sepsis-induced multiple organ failure. Angiotensin (Ang)-(1–7), a biologically active peptide, counteracts various effects of Ang II and attenuates inflammatory responses, reactive oxygen species production, and apoptosis. We evaluated the effects of Ang-(1–7) on organ injury and platelet dysfunction in rats with endotoxaemia. We treated male Wistar rats with saline or lipopolysaccharide (LPS, 10 mg, intravenously) then Ang-(1–7) (1 mg/kg, intravenous infusion for 3 h beginning 30 min after LPS administration). We analysed several haemodynamic, biochemical, and inflammatory parameters, as well as platelet counts and aggregation. Ang-(1–7) improved hypotension and organ dysfunction, and attenuated plasma interleukin-6, chemokines and nitric oxide production in rats after LPS administration. The LPS-induced reduction in platelet aggregation, but not the decreased platelet count, was restored after Ang-(1–7) treatment. The protein expression of iNOS and IκB, but not phosphorylated ERK1/2 and p38, was diminished in Ang-(1–7)-treated LPS rats. The histological changes in liver and lung were significantly attenuated in Ang-(1–7)-treated LPS rats. Our results suggest that Ang-(1–7) ameliorates endotoxaemic-induced organ injury and platelet dysfunction, likely through the inhibition of the inflammatory response and nitric oxide production.

Hydrocortisone decreases lethality and inflammatory cytokine and nitric oxide production in rats challenged with B. anthracis cell wall peptidoglycan

BackgroundLethal B. anthracis infection produces high proinflammatory peptidoglycan (PGN) burdens in hosts. We investigated whether the lethality and inflammation anthrax PGN can produce are related.MethodsAt 6 h before and the start of 24 h anthrax PGN infusions, rats (n = 198) were treated with diluent (controls) or one of three IV-doses of either hydrocortisone (125, 12.5 or 1.25 mg/kg) or TNF-soluble receptor (TNFsr; 2000, 1000 or 333 μg/kg), non-selective and selective anti-inflammatory agents, respectively.ResultsCompared to controls, hydrocortisone 125 and 12.5 mg/kg each decreased 7-day lethality (p ≤ 0.004). Hydrocortisone 125 mg/kg decreased IL-1β, IL-6, TNFα, MCP, MIP-1α, MIP-2, RANTES and nitric oxide (NO) blood levels at 4 and 24 h after starting PGN (except MCP at 24 h). Each decrease was significant at 4 h (except MIP-1α that was significant at 24 h) (p ≤ 0.05). Similarly, hydrocortisone 12.5 mg/kg decreased each measure at 4, 24 and 48 h (except TNFα at 24 h and MIP-1α at 24 and 48 h and NO at 48 h). Decreases were significant for IL-6 and NO at 4 h and RANTES at 48 h (p ≤ 0.05). Hydrocortisone 1.25 mg/kg had non-significant effects. Each TNFsr dose decreased lethality but non-significantly. However, when doses were analyzed together, TNFsr decreased lethality in a potential trend (p = 0.16) and IL-6 and NO significantly at 4 h (p = 0.05).ConclusionsPeptidoglycan-stimulated host inflammation may contribute to B. anthracis lethality.

Fluoride-induced hepatotoxicity is prevented by L-Arginine supplementation via suppression of oxidative stress and stimulation of nitric oxide production in rats

Concerns over fluoride toxicity have increased in recent times due to high exposures from various anthropogenic sources such as industrial sites, fluoride-containing pesticides, drugs, dental products, refridgerants and fire extinguishers. There is, therefore, continued search for agents that could ameliorate the toxicity of this chemical in various body organs. In this study, we sought to investigate the protective effects of L-Arginine (L-Arg), a nitric oxide donor, on liver toxicity induced by sodium fluoride (NaF) in rats. Rats received NaF (300 mg L−1) in drinking water alone or in co-treatment with L-Arg at two different doses, 100 and 200 mg kg−1, by oral gavage, for 7 days. Markers of hepatotoxicity, oxidative stress and antioxidant status were thereafter assessed. NaF caused marked increase in serum transaminases: alanine aminotransferase, Aspartate aminotransferase and Alkaline phosphatase, along with atrophy of the centri-lobular hepatic cords and dilatation of the sinusoids. Moreover, NaF stimulated increases in hepatic contents of hydrogen peroxide (H2O2), nitric oxide (NO), protein carbonyls, malondialdehyde and advanced oxidation protein products. NaF also inhibited the activities of antioxidant enzymes, Glutathione peroxidase and Superoxide dismutase. However, L-Arg supplementation caused significant alleviation of NaF hepatotoxicity by reducing lipid and protein oxidation indices, stimulation of antioxidant systems along with increased production of NO. L-Arg showed promise as a potential protective agent against NaF-induced hepatotoxicity via restoration of oxidant-antioxidant balance. Further studies are required to understand the involvement of NO signaling in the protective effects of L-Arg against fluoride toxicity.

Система образования оксида азота у крыс, перенесших пренатальный стресс

Система образования оксида азота у крыс, перенесших пренатальный стресс

P1534Short time and short term of high-intensity intermittent exercise training reduces arterial stiffness via upregulation of endothelial nitric oxide signalling

Abstract Introduction Conventionally, as an exercise mode which leads to reduction of arterial stiffness, it is well used that moderate-intensity continuous exercise training (MICT). High-intensity interval training (HIIT), such as HIIT program with a total exercise time of 15–30 min is highly time-effective as an exercise mode for which reduces risks of cardiovascular disease. Recent study showed that even shorter HIIT leads to an effective reduction in arterial stiffness. Therefore, HIIT is an effectively exercise therapy which can use in patients with cardiovascular diseases. Although MICT induces vasodilation by acceleration of nitric oxide (NO) production via upregulating arterial endothelial NO synthase (eNOS)/protein kinase B (Akt) signalling pathway, an underlying mechanism of HIIT effects remains unclear. Purpose This study aimed to clarify the effects of short HIIT on arterial stiffness and arterial NO production in rats. Methods Forty 10-week-old male Sprague-Dawley rats were randomly divided into four groups; CON: 8-week sedentary control, MICT: treadmill running for 60 min at 30m/min, 5 days/wk for 8weeks, HIIT: fourteen 20 sec swimming sessions with a weight equivalent to 14–16% of each body weight and 10 sec pause was allowed between exercise sessions, 4 days/wk for 6 weeks from 12-week-old, and RT: ladder climbing, 8–10sets/day, 3 days/wk for 8 weeks groups (n=10 each group). After training session, we measured aortic pulse wave velocity (aortic PWV) as an index of arterial stiffness and plasma nitrite/nitrate (NOx) concentrations and phosphorylation of eNOS and Akt in the aorta. Results Aortic PWV was significantly reduced in both MICT and HIIT groups as compared to CON and RT groups (P<0.05), whereas there was no difference between RT and CON groups. Additionally, arterial phosphorylations of eNOS and Akt and plasma NOx levels were significantly elevated in both MICT and HIIT groups as compared to CON and RT groups (P<0.05), whereas there was no difference between RT and CON groups. Moreover, HIIT-induced reduction of aortic PWV and increase in eNOS and Akt phosphorylations and plasma NOx levels were equal to these MICT effects. Arterial eNOS phosphorylation was negatively correlated with aortic PWV in all groups (r=−0.38, P<0.05). Further study was conducted whether a single-bout high-intensity intermittent exercise accelerates NO production. After acute high-intensity intermittent exercise, plasma NOx levels were significantly elevated (P<0.05). Conclusion These results suggest that HIIT increases NO production via the upregulation of arterial Akt/eNOS signalling pathway, resulting in the reduction of arterial stiffness, despite a reduction in total exercise volume as compared with MICT. Acknowledgement/Funding JSPS KAKENHI (#17H02182 and #16K13059 for M. Iemitsu; #18H06423 for N. Hasegawa)

Effect of spinal cord stimulation on expression of neuronal nitric oxide synthase in rats with diabetic neuropathic pain

Objective To evaluate the effect of spinal cord stimulation on the expression of neuronal nitric oxide synthase(nNOS)in the rats with diabetic neuropathic pain. Methods Forty-eight pathogen-free healthy male Sprague-Dawley rats, aged 2 months, weighing 250-300 g, were divided into 4 groups(n=12 each)using a random number table: control group(group C), diabetes mellitus group(group DM), sham operation group(group S)and spinal cord stimulation group(group SCS). Diabetic neuropathic pain was produced by intraperitoneal injection of 1% streptozocin 75 mg/kg and confirmed by blood glucose level>16.7 mmol/L on day 2 after streptozocin injection.Electrodes were implanted into the epidural space at 19 days after successful establishment of the model in S and SCS groups, and in addition spinal cord stimulation(frequency 50 Hz, pulse width 0.2 ms, intensity=2/3 of the lowest intensity)was performed for 30 min once a day at 26-28 days after successful establishment of the model in group SCS.The mechanical paw withdrawal threshold(MWT)was measured at 1 day before establishment of the model(T1)and 2, 7, 14 and 28 days after successful establishment of the model(T2-5). The rats were sacrificed after the last measurement of MWT at T5, and the lumbar segment of the spinal cord was removed for determination of nitric oxide(NO)content and nNOS expression in spinal cord tissues. Results Compared with group C, the MWT was significantly decreased at T4, 5, and the NO content and nNOS expression in the spinal cord were increased in DM, S and SCS groups(P<0.05). Compared with group DM, the MWT was significantly increased at T5, and the NO content and nNOS expression in the spinal cord were decreased in group SCS(P<0.05). Conclusion The mechanism by which spinal cord stimulation attenuates diabetic neuropathic pain is related to inhibiting nNOS expression and reducing NO production in rats. Key words: Spinal cord; Electrical stimulation therapy; Diabetic mellitus; Neuralgia; Nitric oxide synthase

Tocotrienol alleviates inflammation and oxidative stress in a rat model of spinal cord injury via suppression of transforming growth factor-β.

In recent years accumulating evidence has indicated that tocotrienol exhibits an oxidation resistance function, decreased cholesterol function, inhibits cancer function and has unique physiological functions, including anti-inflammatory, anti-apoptotic and anti-oxidative properties. The present study investigated the effect of tocotrienols on spinal cord injury (SCI) by evaluating oxidative stress, inflammation and inducible nitric oxide synthase (iNOS) in rats. A rat model of SCI was induced by operation. SCI rats were treated with 120 mg/kg/day tocotrienol once a day for eight consecutive weeks. Functional recovery following SCI was measured by using the Basso Beattie Bresnahan (BBB) locomotor rating scale. Then the volume of spinal cord contusions was measured following induction of SCI in the rats. In SCI rats, serum malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase, nuclear factor-κB p65 unit, tumor necrosis factor-α, interleukin (IL)-1β and IL-6 levels were analyzed using respective commercial immunoassay kits. Firstly, iNOS, transforming growth factor (TGF)-β, collagen type IV and fibronectin protein expression levels, in addition to iNOS activity and plasma nitric oxide (NO) production in SCI rats was analyzed using western blot analysis, commercial kits and Griess reagent, respectively. Tocotrienol treatment elevated BBB scores and contused volume in the SCI rats. Tocotrienol protected against SCI with reduced oxidative stress and inflammation, and inhibited iNOS protein expression iNOS activity and plasma NO production in rats. In addition, treatment with tocotrienols suppressed TGF-β, collagen type IV and fibronectin protein expression levels in SCI rats. These results suggest that tocotrienols protect SCI, and suppress oxidative stress, inflammation and iNOS in this model of SCI through TGF-β, collagen type IV and fibronectin signaling pathways.

Spectral analysis of cooling induced hemodynamic perturbations indicates involvement of sympathetic activation and nitric oxide production in rats.

Oscillations in arterial pressure and heart period in response to cold stress are poorly understood. We used a telemetric device with spectral and cross-spectral analyses to assess variabilities in the heart rate (HRV) and blood pressure (BPV) of conscious rats receiving a cooling stimulus (CS) (rapid immersion of palms and soles into 4°C water) at ambient thermoneutral conditions (TC), in a cold room (CC), and when under pentobarbital anesthesia (UA). Power spectra of very low, low, and high frequencies (VLF: 0.02 to 0.2Hz, LF: 0.2 to 0.6Hz, and HF: 0.6 to 3.0Hz), dicrotic notch (Dn) and plasma nitric oxide (NO) levels were measured for statistical comparisons. When compared to resting rats (PreCS), CS evoked in rats the following hemodynamic perturbations: 1) pressor and tachycardia; 2) increases in VLFBPV, LFBPV, HFBPV, and TPBPV but decreases in VLFHRV, LFHRV, and TPHRV; 3) a positive correlation between LFBPV and VLFBPV but an inverse correlation between VLFHRV and VLFBPV and LFHRV and LFBPV; 4) high coherence value at frequency region of LF between BPV and HRV; and 5) increase of NO production and disappearance of Dn. Additionally, CS of CC and UA rats compared with TC rats evoked different patterns of hemodynamic perturbations; CC rats were activated but UA rats were inactivated. Our findings indicate that changes in VLFBPV are related to the myogenic vascular responsiveness to CS. Power spectra changes to CS are highly relevant to sympathetic activation and NO production.

Stimulation of nitric oxide production contributes to the antiplatelet and antithrombotic effect of new peptide pENW (pGlu-Asn-Trp)

IntroductionNew peptide pGlu–Asn–Trp (pENW), initially extracted from snake venom, significantly attenuates the formation of arterial and venous thrombi in vivo, and has modest in-vitro antiplatelet activity. This study was designed to investigate the underlying mechanisms. MethodsThe rat carotid thrombosis model induced by FeCl3 was established to evaluate the antithrombotic activity of pENW. The effects of pENW on the production of nitric oxide (NO), as well as the expression and activity of endothelial nitric oxide synthase (eNOS), were determined. The vasorelaxant effect of pENW was evaluated using isolated rat aortic rings in the absence or presence of NG-nitro-L-arginine methyl ester (L-NAME, eNOS inhibitor). Furthermore, the in-vitro antiplatelet activity of pENW was investigated with the addition of sodium nitroprusside (SNP, NO donor) and/or L-NAME to further prove the role of NO and eNOS in the inhibitory effect of pENW on platelet aggregation. ResultsIn vivo, pENW inhibited thrombus formation induced by endothelial injury in a dose-dependent manner, with a significantly prolonged time to the occurrence of arterial occlusion. It was shown that pENW offered protection for blood vessels from oxidative injury. pENW significantly increased NO production in rats treated with pENW at 4 or 2mg/kg body weight. Furthermore, the production of NO from the cultured vascular endothelial cells was increased with the treatment of 10–4M and 10–5M pENW; pENW also enhanced eNOS expression and activity both in vivo and in vitro, and elicited a concentration-dependent vasorelaxation which was significantly inhibited by L-NAME. Notably, pENW inhibited ADP-induced platelet aggregation, and the inhibition was more significant in the presence of NO. The inhibition of platelet aggregation by pENW was significantly abolished by L-NAME. ConclusionsThe in-vivo antiplatelet and antithrombotic effects of pENW are at least partly mediated by the increased production of endogenous NO via up-regulation and stimulation of eNOS. The findings suggest that pENW could potentially be developed as a novel therapeutic agent in the treatment of platelet-driven disorders.

Combined Effect of Low Magnesium and High Sucrose Diet on Magnesium Status and Nitric Oxide Production in Rats

Dietary magnesium deficiency as well as excess sucrose has been shown to be associated with the generation of reactive oxygen species (ROS). Nitric oxide (NO) and induction of nitric oxide synthase (NOS) are two important markers of nitrosative stress. The present study was planned to investigate the effect of low magnesium diet on magnesium status and nitric oxide production in sucrose fed rats. Male Wistar rats were divided into two groups: a control group (C); and high sucrose low magnesium diet group (HSLM). These animals were studied longitudinally over a period of three months. The urine magnesium excretion exhibited a significant decline in HSLM group. Tissue magnesium profile of various organs revealed that whereas, the magnesium content of liver, muscle and heart showed a significant decrease in the HSLM group, the magnesium content of kidneys, however, exhibit a reverse trend by showing an increase in the HSLM groups. The biochemical analysis showed a significant increase in the plasma nitrite as well as citrulline levels in the HSLM groups. These findings suggest that high sucrose and low magnesium diet may cause nitrosative stress in rats as reflected by increased production of nitric oxide and nitric oxide synthase activity.

Effects of Kaempferol and Myricetin on Inducible Nitric Oxide Synthase Expression and Nitric Oxide Production in Rats

When administered as drugs or consumed as food components, polyphenolic compounds synthesized in plants interfere with intracellular signal transduction pathways, including pathways of nitric oxide synthase expression. However, effects of these compounds in vivo do not always correlate with nitric oxide synthase-inhibiting activities revealed in experiments with cultured cells. The initial goal of this work was to compare effects of flavonoids kaempferol and myricetin on inducible nitric oxide synthase mRNA and protein expression monitored by real-time RT-PCR and immunohistochemistry and to evaluate the impact of these effects on nitric oxide production in rat organs measured by means of electron paramagnetic resonance spectroscopy. Kaempferol and myricetin attenuated the lipopolysaccharide-induced outburst of inducible nitric oxide synthase gene expression; kaempferol also significantly decreased the lipopolysaccharide-induced outburst of inducible nitric oxide synthase protein expression in the liver. Myricetin decreased nitric oxide production in intact rat liver. Kaempferol did not decrease nitric oxide production neither in intact rats nor in the lipopolysaccharide-treated animals. Kaempferol even enhanced the lipopolysaccharide-induced increase of nitric oxide production in blood. Myricetin did not interfere with lipopolysaccharide effects. As both kaempferol and myricetin are known as inhibitors of inducible nitric oxide synthase expression, our results suggest that modifications of nitric oxide level in tissues by these compounds cannot be predicted from data about its effects on nitric oxide synthase expression or activity.

Neonatal administration of N-omega-nitro-l-arginine induces permanent decrease in NO levels and hyperresponsiveness to locomotor activity by d-amphetamine in postpubertal rats

Nitric oxide (NO) is associated with dopamine (DA) release. Previously, we demonstrated that rats treated with a non-selective nitric oxide synthase inhibitor, N-omega-nitro-l-arginine (l-NNA) at postnatal days 4–6 (PD4–6) show increased locomotion and disrupt neuronal cytoarchitecture after puberty (PD60). Here, we investigate whether the modulation of NO production in rats at PD4–6 causes long term changes of NO system, its impact on DA innervation, and schizophrenia-like behaviors. NO levels were measured in seven brain areas at PD35, PD60, PD90, and PD120. Autoradiographic studies explored the effect of l-NNA on the expression of D1 and D2 receptors in the caudate–putamen (CPu) and nucleus accumbens (NAcc) at PD60. Locomotor activity was assessed at PD60 using the non-selective DA agonists, amphetamine and apomorphine, and the selective DA receptor agonist [D2, quinpirole; D3, 7-hydroxy-N,N-di-n-propylaminotetralin ((±)-7-OH-DPAT)]. l-NNA treatment produced decreases in NO levels in the frontal cortex, striatum, brainstem and cerebellum, while in the occipital cortex changes were observed at PD120. Hippocampus and temporoparietal cortex showed differential levels of NO. Receptor autoradiography revealed increases in D1 receptor levels in the NAcc (shell), while decreases in D2 receptor binding were observed in the CPu and NAcc (core). Amphetamine and quinpirole treatments resulted in increases in locomotion. In contrast, treatment with 7-OH-DPAT produced hypolocomotion at low doses, while increased locomotion was seen at the highest dose. These results show that modulation of NO levels early postnatally (PD4–6) produces long term alteration in NO levels, with possible consequences on DA transmission, and related behaviors relevant to schizophrenia.

CAFFEINE DOES NOT MODULATE NUTRITIVE BLOOD FLOW TO RAT GASTRIC SUBMUCOSA - A MICRODIALYSIS STUDY

Coffee irritates the gastric mucosa disrupting its barrier and increasing the risk of peptic ulcers. However, caffeine's contribution to these effects has not yet been elucidated. In this study we looked at the local effect of caffeine on the microcirculation and nitric oxide production in rats together with systemic marker of oxidative stress malondialdehyde as possible mechanisms whereby caffeine might participate in mucosal barrier impairment. Four groups of rats were anesthetized and administered as a bolus four different intraperitoneal doses of caffeine (0, 1, 10 and 50 mg kg(-1) b.wt.). The gastric submucosal microcirculation and nitric oxide production were then recorded for 2.5 hours by in situ microdialysis using the flow marker ethanol. At the completion of the experiments, plasma caffeine and malondialdehyde levels as well as morphological mucosal injury were determined. There were no major differences in the macro- or microscopic pictures of the mucosa among the groups. Local microcirculatory (ethanol out/in ratio) and nitric oxide monitoring failed to demonstrate statistically significant changes as did measurement of plasma malondialdehyde in response to caffeine injections. Caffeine per se seems unlikely to contribute to the gastric mucosal barrier injury associated with coffee consumption by alterations in nutritive blood flow, nitric oxide production or aggravation of systemic oxidative stress. This information is relevant for better understanding of the mechanisms involved in caffeine-mediated influences on gastric physiology in relation to the irritant effects of coffee.

Electron paramagnetic resonance study of nitric oxide production during 5-HT2 receptor blockade in the blood, heart, and liver of rats with myocardial infarction

The effect of serotonin 5-HT2 receptor blockade on nitric oxide production in rats with myocardial infarction was evaluated by the method of electron paramagnetic resonance. The spectra were recorded in samples of the heart tissue (left and right chambers), liver, and blood. 5-HT2 receptor blockade during myocardial infarction was followed by a decrease in the total content of nitrosyl complexes in the spin trap and R and T conformers of Hb-NO. The percent of T conformers increased in the remaining complexes of Hb-NO. These changes were observed in the heart and, particularly, in the blood. The amount of spin-trap complexes was lower in the liver. Hence, nitric oxide molecules were primarily associated with the spin trap in liver tissue. The decrease in the number of Hb-NO complexes in the blood probably reflects the decrease in the severity of hypoxia due to myocardial infarction. A correlation was found between these changes and physiological state of rats. 5-HT2 receptor antagonist improved general state of rats with infarction and increased survival rate.

Inhibition of extracellular signal-regulated kinase (ERK1/2) activity reverses endotoxin-induced hypotension via decreased nitric oxide production in rats

Overproduction of reactive oxygen and nitrogen species leads to oxidative stress and decreased total antioxidant capacity, which is responsible for high mortality from several inflammatory diseases such as endotoxic shock. Among reactive nitrogen species, nitric oxide (NO) produced by inducible NO synthase (iNOS) during endotoxemia is the major cause of vascular hyporeactivity, hypotension and multiple organ failure. This study was conducted to determine if mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK1/2) contributes to endotoxin-induced hypotension as well as vascular inflammation and oxidative stress via NO production. In conscious male Wistar rats, injection of endotoxin (10 mg kg −1, i.p.) caused a decrease in mean arterial pressure (MAP) for 4 h and increased levels of nitrite in serum, aorta and mesenteric artery. These effects of endotoxin were prevented by selective inhibition of ERK1/2 phosphorylation by MAPK kinase (MEK1/2) with U0126 (5 mg kg −1, i.p.; 1 h after endotoxin). Endotoxin also caused an increase in protein levels of phosphorylated ERK1/2 in aorta which was abolished by U0126. Selective inhibition of iNOS with phenylene-1,3-bis[ethane-2-isothiourea] dihydrobromide (1,3-PBIT) (10 mg kg −1, i.p.; 1 h after endotoxin) did not change the endotoxin-induced increase in ERK1/2 activity. Myeloperoxidase activity was increased in aorta and decreased in mesenteric artery by endotoxin, which was reversed by U0126. Endotoxin-induced decrease in one of the products of lipid peroxidation, malonedialdehyde (MDA) was prevented by U0126 in mesenteric artery; however, U0126 caused a further decrease in the levels of MDA in aorta. These data suggest that increased phosphorylation of ERK1/2 by MEK1/2 contributes to the endotoxin-induced hypotension via NO production rat aorta and mesenteric artery. It is likely that ERK1/2 mediates the effect of endotoxin on MPO activity in a different degree in the tissues suggesting possible involvement of any mediator and/or mechanism which also causes neutrophil infiltration during inflammatory response at least in mesenteric artery. Moreover, ERK1/2 seems to be involved in the endotoxin-induced increase in total antioxidant capacity in mesenteric artery.

Alteration of Nitric Oxide Production in Rats Exposed to a Prolonged, Extremely Low-Frequency Magnetic Field

The purpose of this study is to investigate the possible effect of an extremely low-frequency magnetic field (ELF-MF) on nitric oxide (NO) level. In this study, 27 male Sprague-Dawley rats were used. The rats were divided into three groups: two experimental and one control (sham-exposed). The first and second experimental group (n = 10) were exposed to 100 µT and 500 µT ELF-MF during 10 months, 2 h a day, respectively, and the third (n = 7) group was treated like an experimental group except for ELF-MF exposure in methacrylate boxes. After ELF-MF and sham exposure, serum nitrite levels were measured by Griess reaction. A significant reduction was observed in nitrite levels among the first and second experimental groups of rats and sham-exposed rats after exposure for 10 months, 2 h a day, to ELF-MF of 100 and 500 µT (p < 0.01). These results suggest that prolonged ELF-MF exposure at intensities of exposure limits, determined by ICNIRP for public and occupational, may reduce NO production probably affected by NO generation pathways.

Role of inducible nitric oxide synthase expressed by alveolar macrophages in High Mobility Group Box 1- induced acute lung injury

The role of inducible nitric oxide synthase (iNOS) expressed by alveolar macrophages in acute lung injury induced by high mobility group box 1 (HMGB1) was explored. Primary rat alveolar macrophages (PRAMs) were stimulated with HMGB1 to analyze iNOS expression. Alveolar macrophages and iNOS were inhibited by gadolinium chloride and 1400W in rats challenged by HMGB1 intratracheally. Western Blot was applied to assay iNOS expression in PRAMs. Indices for acute lung injury in rats were measured. Immunocytochemistry was used to localize iNOS in squarebronchoalveolar lavage (BAL) cells. The enzyme activities of iNOS and constitutive nitric oxide synthase (cNOS) for BAL cells were determined. A time- and concentration-dependent response of iNOS expression in PRAMs to HMGB1 induction was observed. Intratracheal instillation of HMGB1 produced persistently exacerbated acute lung inflammation, induction of iNOS in alveolar macrophages and increased lung nitric oxide production in rats. Abrogation of iNOS or macrophages attenuated lung inflammation, nitric oxide in BAL fluid, and iNOS activity of BAL cells, but had no significant effect on cNOS activity of BAL cells in rats challenged by HMGB1. Inducible nitric oxide synthase expressed by alveolar macrophages facilitates the development of HMGB1-induced acute lung injury.

Blood Pressure Relationship to Nitric Oxide, Lipid Peroxidation, Renal Function, and Renal Blood Flow in Rats Exposed to Low Lead Levels

The results of experiments designed to show that inhibition of nitric oxide production in rats exposed to low lead levels increases vascular resistance, decreases renal blood flow and glomerular function, and enhances oxidative stress. Forty-five adult male Sprague-Dawley rats were divided into four groups. Group A was used as controls and consisted of rats that received no treatment; group B acted as NO-inhibited controls by receiving L-NAME (N(G)-nitro-l-arginine methyl ester) as the NO inhibitor; group C was injected intraperitoneally with 8 mg/kg lead acetate for 2 wk; and group D receiving lead acetate plus L-NAME. Compared to healthy controls, significant elevation of the mean (p<0.01), systolic (p<0.04), and diastolic (p<0.01) blood pressures was found in the lead-treated rats. The renal blood flow was 1550+/-468 blood per unit (bpu) in the controls, 488+/-220 bpu in the L-NAME controls, 1050+/-458 bpu in the lead-treated group, and 878+/-487 bpu in the Pb plus L-NAME group. Low-level lead exposure did not change the urinary flow rate, creatinine clearance, and the creatinine, potassium, phosphorus, glucose, and protein excretion in 24-h urine. In the lead plus NO-inhibited rats, a significant decrease in sodium ion excretion was observed (p<0.01). The NO levels of the lead exposed, L-NAME-treated controls, and L-NAME plus lead-exposed groups are significantly lower compared to untreated controls: p<0.002, p<0.001, and p<0.01, respectively. When compared to untreated controls, the plasma malondialdehyde levels were not significantly different in the lead exposed, lead plus L-NAME, and L-NAME control groups. These results suggest that lead-induced hypertension might be related to a decrease of NO and consequent vasoconstriction, rather than to a decrease of renal blood flow or to decreases in renal sodium.

FK506 abrogates delayed neuronal death via suppression of nitric oxide production in rats

Background and purpose: The mechanism of the neuroprotective effect of FK506 in relation to nitric oxide (NO) production has not been clarified in vivo. We have investigated the effect of FK506 on ischemia-induced NO production in association with the pathogenesis of delayed neuronal death (DND) in rats. Methods: In vivo microdialysis was performed in the hippocampus of male Sprague–Dawley rats (250–350 g). Dialysate samples were collected every 3 min. In the ischemia group ( n=16), global ischemia was induced for 21 min and reperfusion was achieved. In the FK506 treatment group ( n=25), FK506 (1 mg/kg, i.v.) was administered 21 min prior to the onset of global ischemia. Sham operations were done ( n=15). The levels of NO 2 − in the dialysate samples were determined by the Griess reaction. The animals were decapitated 7 days after ischemia. Coronal brain sections were stained with hematoxylin and eosin. Results: In the ischemia group, the NO 2 − level significantly increased during ischemia. In the FK506 treatment group, there was no significant change in the NO 2 − level during ischemia. In histological examinations, FK506 treatment showed a neuroprotective effect against DND. Conclusions: The effect of FK506 inhibiting NO production contributes to the neuro-protective effect of FK506 on DND in the hippocampus.