SEARCH · PubMed Health

Results for “Nitrites”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources

PubMed1996

Determination of nitrite in human blood by combination of a specific sample preparation with high-performance anion-exchange chromatography and electrochemical detection.

All photometric or HPLC methods described to date have been unable to detect nitrite, a reliable marker of NO synthase activity, in human blood because of its rapid metabolism within the erythrocytes. We now elaborate on method to prevent nitrite degradation during sample preparation which in combination with high-performance anion-exchange chromatography and electrochemical detection allows a sensitive measurement of nitrite. A linear current response in the concentration range of 10-1000 nmol/l nitrite was observed yielding a correlation coefficient of 0.99. In addition, the combination of the electrochemical with a UV detector allowed us to simultaneously quantify nitrate within one analytical run, which is the end product of NO/nitrite metabolism. Basal levels for nitrate and nitrite in human blood were determined with 25 +/- 4 mumol/l and 578 +/- 116 nmol/l (n = 8), respectively and thus were in the same concentration range as expected from NO measurement in saline perfused isolated organs or cultured endothelial cells. Therefore, the presented method may be used to assess activity of endothelial constitutive NO synthase in humans under physiological and pathophysiological conditions.

Biomarkers↗

PubMedDate not supplied

Can urinary nitrite results be used to guide antimicrobial choice for urinary tract infection?

Enterococcus is unable to reduce nitrates and is also considered clinically resistant to trimethoprim/sulfamethoxazole (TMP/SMX), the drug of choice for uncomplicated urinary tract infection (UTI). The purpose of this study was to determine whether urinalysis nitrite results can be used to guide antimicrobial therapy when treating UTI in the emergency department (ED). A retrospective chart review examined 159 university hospital ED outpatients who had signs or symptoms of UTI and had a urinalysis with positive culture. Patients were categorized into two groups based on nitrite results. The proportion of isolates sensitive to TMP/SMX in each group was compared by using a two-sample z-test. Eighty-six urinalyses were nitrite positive: 67 (78%) contained TMP/SMX-sensitive isolates. Seventy-three urinalyses were nitrite negative; 60 (82%) contained sensitive isolates. There was no statistically significant difference in the proportion of isolates sensitive to TMP/SMX. Thus, we conclude that emergency physicians should not adjust antibiotic therapy for UTI based on nitrite results.

Adult↗

PubMed2000

Nitrite generation and antioxidant effects during neutrophil apoptosis.

Neutrophil apoptosis is important for the resolution of airway inflammation in a number of lung diseases. Inflammatory mediators, endogenous reactive oxygen and nitrogen species, and intracellular and extracellular antioxidants may all influence neutrophil apoptosis. This study investigated the involvement of these factors during apoptosis of neutrophils cultured in vitro. Neutrophils undergoing spontaneous apoptosis in culture as assessed by annexin V binding generated significant amounts of nitrite. Incubation with agonistic anti-Fas monoclonal antibody or tumor necrosis factor-alpha (TNF-alpha) enhanced neutrophil apoptosis at 6 h, although it decreased nitrite accumulation. Although granulocyte-macrophage colony-stimulating factor significantly reduced neutrophil apoptosis, this was also associated with decreased nitrite accumulation. In contrast, inhibition of apoptosis at 16 h by dibutyryl cyclic adenosine monophosphate was associated with increased nitrite accumulation. Exogenous glutathione (GSH) or N-acetylcysteine significantly enhanced neutrophil apoptosis at 6 h and stimulated the production of H(2)O(2), which may mediate apoptosis through intracellular hydroxyl radical production. Intracellular GSH concentrations decreased in neutrophils undergoing apoptosis, and this was more marked in neutrophils treated with anti-Fas or TNF-alpha. These results suggest a causal association between reduced endogenous nitric oxide production, reduced intracellular GSH, and Fas- and TNF-alpha-mediated neutrophil apoptosis, whereas enhanced neutrophil survival mediated by dibutyryl cyclic adenosine monophosphate is associated with increased nitrite generation and maintenance of intracellular GSH. The interaction of endogenous reactive oxygen species with extracellular antioxidants such as GSH could also contribute to the complex processes regulating neutrophil apoptosis and hence the resolution of inflammation in the lung.

Acetylcysteine↗

PubMed1998

Lactoperoxidase-catalyzed oxidation of melanin by reactive nitrogen species derived from nitrite (NO2-): an EPR study.

The reaction of synthetic DOPA melanin (DM) with lactoperoxidase (LPO), hydrogen peroxide, and nitrite (NO2-) has been investigated using EPR. We observed that in the presence of nitrite LPO/H2O2 generated large amount of melanin radicals, as evidenced by a strong, up to 11-fold, increase in the intensity of the melanin EPR signal. In contrast, when nitrite was omitted the increase was much less, ca. 30%, which, nevertheless, indicates that DM can be metabolized directly by LPO/H2O2. When the nitrite was present, the concentration of melanin radicals was linearly dependent on [NO2-] (for [NO2-] <5 mM), and increased when [LPO] and [H2O2] increased (at constant [NO2-]). We propose that the mechanism for the generation of melanin radicals by the LPO/H2O2/nitrite system involves oxidation of NO2- by LPO/H2O2 to a reactive metabolite, most likely the nitrogen dioxide radical (.NO2), which subsequently reacts with melanin 5,6-dihydroxyindole subunits producing the respective semiquinone radicals. Because melanin and .NO2 generating systems (nitrite, peroxidase enzymes, hydrogen peroxide) may coexist in cells in vivo, our results suggest that melanin could function as a natural scavenger of this highly reactive nitrogen species. This property may be relevant to the physiological functions of the melanin pigments in vivo.

Catalysis↗

PubMed1998

Specific S-nitrosothiol (thionitrite) quantification as solution nitrite after vanadium(III) reduction and ozone-chemiluminescent detection.

Increasing evidence suggests that S-nitrosothiols (thionitrites) might represent naturally occurring nitric oxide surrogates and function as intermediates in nitrogen monoxide metabolism. A facile, sensitive, and selective micromethod has been developed and validated for quantification of S-nitrosothiols as their mercury-displaceable nitrogen monoxide content. In this method, brief (5-min), room-temperature pretreatment of S-nitrosothiol with a molar excess of aqueous mercuric chloride was used to liberate into solution, quantitatively, the nitrogen monoxide moiety, which rapidly and quantitatively converted to its stable solution end-product, nitrite. Solution nitrite was reduced back to nitric oxide with vanadium(III), and the nitric oxide was detected by gas-phase chemiluminescence after reaction with ozone in a commercial nitric oxide analyzer. A linear relationship was observed between S-nitrosothiol-bound nitrogen monoxide and ozone-chemiluminescent detector response over a wide range (16.3-3500 pmol) of nitric oxide, as generated by reaction of vanadium(III) with either nitrite standard or mercury-treated S-nitrosothiol. Assay response was quantitatively identical for equivalent amounts of nitrite and S-nitrosothiol-bound nitrogen monoxide. The method displayed 96% selectivity for nitrite vs. nitrate and negligible (<2%) interference by nitrosated compounds bearing nitrogen monoxide moieties bound to either nitrogen or carbon. The lower limits of quantitative sensitivity and qualitative detection were below 50 and 20 pmol S-nitrosothiol-bound nitrogen monoxide-equivalents, respectively. The intraday and interday coefficients of variation did not exceed 8%. This technique has been applied to quantify structurally diverse natural and synthetic S-nitrosothiols with quantitative recovery from complex biological samples such as culture media and plasma at levels of nitrogen monoxide-equivalents undetectable by the popular Saville colorimetric method.

Humans↗

PubMed1998

Inhibitory effects of citrus fruits on the mutagenicity of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid treated with nitrite in the presence of ethanol.

It has been shown that the mutagenicity of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCCA), a mutagen precursor in soy sauce treated with nitrite, was strongly increased when it was treated with nitrite in the presence of alcohols. We found that the mutagenicity of MTCCA treated with 50 mM nitrite at pH 3, 37 degrees C for 60 min in the presence of 7.5% ethanol was reduced by the addition of citrus fruits sudachi (Citrus sudachi), lemon (C. limon) and yuzu (C. junos), to the reaction mixture. The mutagenicity-reducing activity per weight of flavedos (outer colored portions of peel) of the citrus fruits was considerably higher than that of the juices. The juices of the other citrus fruits commercially available in Japan also had mutagenicity-reducing activity against the nitrite-treated MTCCA. Among the many components of citrus fruits, dietary fibers lignin and pectin showed strong antimutagenic activity in the reaction mixture, suggesting that the mixed fractions of these components including lignin, pectin, D-limonene, naringin, hesperidin, ascorbic acid and citric acid reduce the mutagenicity of MTCCA in the reaction mixture containing nitrite and ethanol.

Animals↗

PubMed2002

Effect of acetaminophen on the myeloperoxidase-hydrogen peroxide-nitrite mediated oxidation of LDL.

Myeloperoxidase, in the presence of hydrogen peroxide and nitrite, promotes the lipid peroxidation of low density lipoprotein (LDL); the modified lipoprotein is then capable of being readily endocytosed by macrophages. Since acetaminophen has been shown to inhibit the leukocyte myeloperoxidase antimicrobial system and is, under certain experimental conditions, an antioxidant, the effect of acetaminophen on the myeloperoxidase-hydrogen peroxide-nitrite mediated oxidation of LDL was examined. The content of LDL lipid hydroperoxides after incubation with 50 nM myeloperoxidase, 100 microM nitrite and a hydrogen peroxide generating system for 6 h was reduced by approx. 80% in the presence of 25-250 microM acetaminophen. The production of thiobarbituric acid-reactive substances was also inhibited by acetaminophen to a similar extent. Acetylsalicylic acid (25-100 microM) did not inhibit LDL lipid peroxidation mediated by the myeloperoxidase enzyme system. LDL, treated with myeloperoxidase, hydrogen peroxide and nitrite for 14 h, was metabolized by macrophages to a much greater extent than native LDL. The presence of acetaminophen prevented the modification of LDL; the lipoprotein was metabolized by macrophages to the same extent as was native LDL. These results demonstrate that acetaminophen is a potent inhibitor of the myeloperoxidase-hydrogen peroxide-nitrite mediated modification of LDL.

Acetaminophen↗

PubMed2002

Measurement of S-nitrosoalbumin by gas chromatography--mass spectrometry. III. Quantitative determination in human plasma after specific conversion of the S-nitroso group to nitrite by cysteine and Cu(2+) via intermediate formation of S-nitrosocysteine and nitric oxide.

Highly contradictory data exist on the normal plasma basal levels in humans of S-nitrosoproteins, in particular of S-nitrosoalbumin (SNALB), the most abundant nitric oxide (.NO) transport form in the human circulation with a range of three orders of magnitude (i.e., 10 nM-10 microM). In previous work we reported on a GC-MS method for the quantitative determination of SNALB in human plasma. This method is based on selective extraction of SNALB and its 15N-labeled SNALB analog (S(15)NALB) used as internal standard on HiTrapBlue Sepharose affinity columns, HgCl(2)-catalysed conversion of the S-nitroso groups to nitrite and [15N]nitrite, respectively, their derivatization to the pentafluorobenzyl derivatives and quantification by GC-MS. By this method we had measured SNALB basal plasma levels of 181 nM in healthy humans. It is generally accepted that HgCl(2)-catalysed conversion of S-nitroso groups into nitrite is specific. In consideration of the highly divergent SNALB plasma levels in humans reported so far, we were interested in an additional method that would allow specific conversion of S-nitroso groups into nitrite. We found that treatment with cysteine plus CuSO(4) is as effective and specific as treatment with HgCl(2). The principle of the cysteine/CuSO(4) procedure is based on the transfer of the S-nitroso group from SNALB to cysteine yielding S-nitrosocysteine, and its subsequent highly Cu(2+)-sensitive conversion into nitrite via intermediate.NO formation. Similar SNALB concentrations in the plasma of 10 healthy humans were measured by GC-MS using HgCl(2) (156+/-64 nM) and cysteine/CuSO(4) (205+/-96 nM). Our results strongly suggest that SNALB is an endogenous constituent in human plasma and that its concentration is of the order of 150-200 nM under physiological conditions.

Animals↗

PubMed2002

Determination of nitrate and nitrite by high-performance liquid chromatography in human plasma.

A new, accurate, fast and simple method has been implemented by which nitrite and nitrate ions, as stable forms of nitric oxide production were studied. A study of these two ions was carried out by a sensitive and accurate HPLC method with two detectors. The most important advantages of the reported method are: short time of analysis, minimal sample pre-treatment, long life of the analytical column and stable eluent solution. The photodiode array UV-Vis detector detected nitrite and nitrate ions at an absorbance of 212 nm. Much more sensitive electrochemical detection with a WE (glassy carbon) electrode was used for the detection of nitrite ions. An analytical chromatographic column was formed by a sorbent, containing strong base anion-exchange groups bound in Cl(-) form in the hydrophilic hydroxyethyl methacrylate matrix. The anions were analysed in human plasma without deproteinization using 0.02 M sodium perchlorate monohydrate as eluent solution at pH 3.9. At this pH organic substances do not affect the analysis. The retention times for nitrite and nitrate were 3.62 and 3.72 min (by electrochemical detection) and 4.44 min, respectively. The method was linear (r=0.9992, 0.9998, 0.996) within a 1-100 (nitrate), 1-20 micro mol/l (nitrite) concentration range.

Adult↗

PubMedDate not supplied

Nitrite inhibition of Vitreoscilla hemoglobin (VHb) in recombinant E. coli: direct evidence that VHb enhances recombinant protein production.

Bacteria engineered with the gene (vgb) encoding Vitreoscilla hemoglobin (VHb) typically produce more protein than unengineered cells, and it has generally been assumed that VHb is responsible for this effect. Here, using matched strains of E. coli that bear a recombinant alpha-amylase gene (MK57) or the alpha-amylase gene and vgb (MK79), we provide evidence supporting this assumption. Sodium nitrite (which is known to inhibit heme proteins) was tested over a range of concentrations regarding effects on growth, alpha-amylase production, respiration, and VHb function in MK57 and MK79. Nitrite concentrations were identified at which respiration of cell membranes was inhibited only slightly and to approximately equal degrees in both strains, while whole cell respiration was inhibited to a greater extent and about twice as much in MK79 as MK57. This suggests that these concentrations inhibit VHb while having a much smaller effect on cytochrome oxidase. Direct measurements of VHb showed, in fact, that the same nitrite concentrations greatly decreased the levels of active (ferrous) and, to a somewhat lesser extent, total (ferrous plus ferric) VHb in MK79. Finally, these same nitrite concentrations reversed the advantage regarding alpha-amylase production of MK79 over MK57 seen at 0 mM nitrite, linking the presence of active VHb with the increase in alpha-amylase production.

Escherichia coli↗

PubMed2007

Redox-state-dependent complex formation between pseudoazurin and nitrite reductase.

Bacterial copper-containing nitrite reductase catalyzes the reduction of nitrite to nitric oxide as part of the denitrification process. Pseudoazurin interacts with nitrite reductase in a transient fashion to supply the necessary electrons. The redox-state dependence of complex formation between pseudoazurin and nitrite reductase was studied by nuclear magnetic resonance spectroscopy and isothermal titration calorimetry. Binding of pseudoazurin in the reduced state is characterized by the presence of two binding modes, a slow and a fast exchange mode, with a K(d)(app) of 100 microM. In the oxidized state of pseudoazurin, binding occurs in a single fast exchange mode with a similar affinity. Metal-substituted proteins have been used to show that the mode of binding of pseudoazurin is independent of the metal charge of nitrite reductase. Contrary to what was found for other cupredoxins, protonation of the exposed His ligand to the copper of pseudoazurin, His81, does not appear to be involved directly in the dual binding mode of the reduced form. A model assuming the presence of a minor form of pseudoazurin is proposed to explain the behavior of the complex in the reduced state.

Alcaligenes faecalis↗

PubMed2006

Biogenic amine formation and nitrite reactions in meat batter as affected by high-pressure processing and chilled storage.

Changes in biogenic amine formation and nitrite depletion in meat batters as affected by pressure-temperature combinations (300 MPa/30 min/7, 20, and 40 degrees C), cooking process (70 degrees C/30 min), and storage (54 days/2 degrees C) were studied. Changes in residual nitrite concentration in raw meat batters were conditioned by the temperature and not by the pressure applied. Cooking process decreased (P < 0.05) the residual nitrite concentration in all samples. High-pressure processing and cooking treatment increased (P < 0.05) the nitrate content. Whereas protein-bound nitrite concentration decreased with pressure processing, no effect was observed with the heating process of meat batters. High-pressure processing conditions had no effect on the rate of residual nitrite loss throughout the storage. The application of high pressure decreased (P < 0.05) the concentration of some biogenic amines (tyramine, agmatine, and spermine). Irrespective of the high processing conditions, generally, throughout storage biogenic amine levels did not change or increased, although quantitatively this effect was not very important.

Animals↗

PubMed2005

The acid-promoted reaction of the green tea polyphenol epigallocatechin gallate with nitrite ions.

Exposure of 400 microM (-)-epigallocatechin-3-O-gallate (EGCG), the main polyphenolic constituent of green tea, to equimolar concentrations of nitrite ions in 0.5 M HCl at 37 degrees C resulted in the formation of a distinct pattern of products that were trapped as phenazine derivatives by treatment with o-phenylenediamine. Repeated chromatographic fractionation eventually allowed isolation of four main species, which were identified by 2D NMR and MS analysis as 1b, derived from EGCG quinone 1a, the isomeric oximes 2b,c, arising from nitrosation of EGCG on the pyrogallol B-ring, and the dioxime 4b in which the A-ring was doubly substituted. At lower EGCG concentrations (e.g., 25 microM) and at pH 3, reaction with equimolar amounts of nitrite gave 1b as the first formed species, whereas nitrosation products 2b,c and 4b became detectable only with excess nitrite. Similar reaction of chemically prepared 1a with acidic nitrite led to the formation of 2b,c and 4b, suggesting that this quinone may be an intermediate in the nitrosation of EGCG. Exposure of green tea extracts to acidic nitrite ions resulted in the conversion of EGCG to 1a, detected as 1b. Overall these results substantiate literature reports suggesting that the protective effects of EGCG against nitrosation involve mainly an initial redox exchange process and hint at a hitherto unrecognized property of quinone 1a as a potential scavenger of nitrosating species.

Catechin↗

PubMed2002

Does serum nitrite concentration reflect gastric carcinogenesis in Japanese Helicobacter pylori-infected patients?

This study investigated whether the serum nitrite concentration reflects Helicobacter pylori-induced inflammation and atrophic changes of gastric mucosa. Ninety-seven patients underwent biopsy of both antrum and fundus. Samples were analyzed by the rapid urease test and histopathological examination according to the updated Sydney system. Fasting serum samples from each subject were analyzed for specific IgG Helicobacter pylori antibodies, pepsinogen I and II concentrations, and NO2-/NO3- content. Eleven patients had H. pylori eradicated with proton pump-based triple therapy. There was a strong positive correlation between the Helicobacter pylori density in the gastric mucosa and the serum nitrite concentration, but a negative correlation existed between the atrophic grade of the gastric mucosa and both serum nitrite concentration and Helicobacter pylori density in the gastric mucosa. Serum nitrite concentrations decreased significantly after successful eradication of Helicobacter pylori. Therefore, serum nitrite concentration may be a useful marker for oxidative DNA damage and apoptosis associated with Helicobacter pylori infection.

Antibodies, Bacterial↗

PubMed2003

Monitoring the impact of dissolved oxygen and nitrite on anoxic biofilm in continuous denitrification process.

An anoxic biofilm involved in continuous denitrification process was monitored to investigate the effect of different concentrations of influent dissolved oxygen (DO) or nitrite on the biofilm. Microelectrode measurements evidenced nitrate removal activity of biofilm. When different concentrations of DO were applied to the reactor, generally decreased concentrations of DO were observed as bed depth increased from the bottom of the reactor. Greatest decrease of the DO was observed in the lower 20% of the bed depth. Nitrate removal efficiency was inversely proportional to influent DO concentrations (8.3-11.9 DO mg L(-1)) or nitrite loading rates (0-5.5 N-NO2- kg m(-3) day(-1)) employed in this study. Nitrite loading rates to achieve more than 90% of nitrate removal efficiency were 1.46 N-NO2- kg m(-3) day(-1) or less at pH 7.5 and 0.34 N-NO2- kg m(-3) day(-1) or less at pH 6.8. Nitrate removal efficiency was 63% or more within the lower 20% of the bed depth at the nitrite loading rates that allowed more than 90% of nitrate removal efficiency of the reactor. The results of this study provide first quantitative data that nitrate removal performance of an anoxic biofilm is inhibited by DO or nitrite, reported to be a limiting factor in the suspended biological denitrification process.

Biofilms↗

PubMed2003

Does intragastric nitrite concentration reflect gastric carcinogenesis in Japanese Helicobacter pylori-infected patients?

Established risk factors for gastric cancer include a diet high in nitrate or nitrite and low in vitamin C and the presence of achlorhydria or hypochlorhydria. The aim of this study was to investigate the relationship between intragastric nitrite concentration and atrophic change of the stomach or gastric carcinogenesis in Japanese Helicobacter pylori-infected patients. Gastric juice pH, nitrite, and total vitamin C concentrations in gastric juice, serum pepsinogen I and II concentrations, and specific Helicobacter pylori antibody were analyzed. Intragastric total vitamin C concentration was decreased by Helicobacter pylori infection of the gastric mucosa and with progression of the atrophic grade. There was a significant positive correlation between atrophic grade and intragastric nitrite concentration. In conclusion, the levels of nitrite in gastric juice play a causal role in the development of cancer in Helicobacter pylori-associated atrophic gastric mucosa.

Adolescent↗

PubMed2003

Alterations of nitrate and nitrite content in saliva, serum, and urine in patients with salivary dysfunction.

BACKGROUND: The role of the salivary glands in the maintenance of nitrate and nitrite in saliva is poorly understood. The aim was to study alterations of nitrate and nitrite metabolisms in patients with Sjogren's syndrome (SS) or sialosis. METHODS: Saliva, serum, and urine samples were collected from healthy volunteers (n = 29), patients with SS (n = 31), and patients with sialosis (n = 30). Concentrations of nitrate and nitrite were determined by high-performance liquid chromatography (HPLC). RESULTS: In the healthy group, the highest concentration of nitrate was found in parotid saliva (172 mg/l), followed by urine (160 mg/l), whole saliva (97 mg/l), and serum (33 mg/l). In the SS group, concentration of nitrate was decreased in parotid saliva and whole saliva, and increased significantly in urine. Concentration of nitrite in whole saliva was significantly decreased in the SS group and increased in the sialosis group. CONCLUSION: Hypofunction of the salivary glands is associated with significant changes of nitrate and nitrite levels in the saliva and urine.

Adolescent↗

PubMed1999

Structure of cytochrome c nitrite reductase.

The enzyme cytochrome c nitrite reductase catalyses the six-electron reduction of nitrite to ammonia as one of the key steps in the biological nitrogen cycle, where it participates in the anaerobic energy metabolism of dissimilatory nitrate ammonification. Here we report on the crystal structure of this enzyme from the microorganism Sulfurospirillum deleyianum, which we solved by multiwavelength anomalous dispersion methods. We propose a reaction scheme for the transformation of nitrite based on structural and spectroscopic information. Cytochrome c nitrite reductase is a functional dimer, with 10 close-packed haem groups of type c and an unusual lysine-coordinated high-spin haem at the active site. By comparing the haem arrangement of this nitrite reductase with that of other multihaem cytochromes, we have been able to identify a family of proteins in which the orientation of haem groups is conserved whereas structure and function are not.

Crystallography, X-Ray↗