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PubMed1997

Changes in nitric oxide generated by the oxidation of oxymyoglobin by nitrite.

We found that nitric oxide (NO) was produced during the oxidation of oxymyoglobin by nitrite, by using a NO-selective electrode system, which enabled us to measure NO in phosphate solution, continuously and quantitatively. When 500 microM nitrite was added in the solution of oxymyoglobin (65 microM in heme), oxymyoglobin was oxidized to metmyoglobin in a sigmoidal manner. During the reaction, NO was generated quickly at the initial lag phase, and reached its peak (NO approximated to 30 microM), before the burst oxidation of oxymyoglobin occurred. Then, NO content was gradually decreased. By the addition of the increased concentration of nitrite (1 mM or 2 mM) to oxymyoglobin solution (65 microM in heme), the production rate of NO was much accelerated and the amounts of NO were increased, in good accordance with the accelerated oxidation of oxymyoglobin by nitrite. These results suggest that NO is involved in the oxidation of oxymyoglobin by nitrite.

Animals↗

PubMed1981

Studies on nitrosamine formation by the interaction between drugs and nitrite. I. Measurement of the amount of nitrosamine formed in rat and guinea pig stomachs.

The amounts of nitrosamine formed by the interaction of several drugs and nitrite in rat and guinea pig stomachs were estimated. The nitrosamine formation from aminopyrine and nitrite was much more in guinea pig stomachs than in rat stomachs. It seemed that this result was due to the difference in gastric contents of these animals. As the nitrosamine formation was also indicated in the interaction of a clinically prescribed dose of aminopyrine and very low doses of nitrite in rat and guinea pig stomachs, there is a possibility that the nitrosation of aminopyrine takes place in human stomachs, too. Minocycline also interacted with nitrite and formed N-nitrosodimethylamine. However, the amount of nitrosamine formed was less in minocycline than in aminopyrine. Oxytetracycline was not found to form nitrosamine in the stomachs of these animals. The effects of several compounds on the nitrosamine formation by the interaction of aminopyrine and nitrite were also investigated. Ascorbic acid, sodium erythorbate, propyl gallate and butylated hydroxyanisole reduced the nitrosamine formation but the effect of alpha tocopherol, sorbic acid and butylated hydroxytoluene was not observed in the stomach.

Aminopyrine↗

PubMed2006

Controlling the nitrite:ammonium ratio in a SHARON reactor in view of its coupling with an Anammox process.

The combined SHARON-Anammox process for treating wastewater streams with high ammonia load is the focus of this paper. In particular, partial nitritation in the SHARON reactor should be performed to such an extent that a nitrite:ammonium ratio is generated which is optimal for full conversion in an Anammox process. In the simulation studies performed in this contribution, the nitrite:ammonium ratio produced in a SHARON process with fixed volume, as well as its effect on the subsequent Anammox process, is examined for realistic influent conditions and considering both direct and indirect pH effects on the SHARON process. Several possible operating modes for the SHARON reactor, differing in control strategies for O2, pH and the produced nitrite:ammonium ratio and based on regulating the air flow rate and/or acid/base addition, are systematically evaluated. The results are quantified through an operating cost index. Best results are obtained by means of cascade feedback control of the SHARON effluent nitrite:ammonium ratio through setting an O2 set-point that is tracked by adjusting the air flow rate, combined with single loop pH control through acid/base addition.

Air Movements↗

PubMed2006

Achieving biological nitrogen removal via nitrite by salt inhibition.

The principal aim of this paper is to develop and evaluate an approach to obtain nitrogen removal bypassing nitrate. The method is based on the addition of sodium chloride (NaCI), selective inhibitor of nitrite oxidizers, to influent. Validation of the new method was conducted on laboratory-scale experiments applying the SBR activated sludge process to domestic wastewater with low C/N ratio. With the aerobic-anoxic sequence, three parallel SBRs achieving complete nitrification-denitrification are dosed by a certain concentration of NaCI to influent. The high nitrite accumulation, depending on the salinity in the influent and the application duration of salt, was obtained in SBRs treating saline wastewater. Optimum dosage and application duration of salt, which interact to determine the performance and stabilization of nitrite accumulation, were determined by experiment. In order to evaluate the method, the response of the biological treatment system to salt concentration was also explored. The repeatability of the method was further verified under various operational conditions. Microbial population tests supported the presumption that nitrite oxidizers are inhibited by salt addition and washed out of the system. The presented method is valuable to offer a solution to realize nitrogen removal via nitrite under normal conditions.

Bacteria↗

PubMedDate not supplied

High nitrite buildup during nitrification in a rotating disk reactor.

Incomplete nitrification with high nitrite accumulation has three practical advantages: lower oxygen consumption, less need for organics for denitrification, and lower sludge production during denitrification. Nitrification leading to high nitrite formation was experimentally studied in a continuous single rotating disk reactor (RDR) and compared to a modeled continuous completely stirred tank reactor (CSTR). The results of this model show that to accumulate nitrite greater than 50% at oxygen levels higher than 3.5 mg O2/L, pH levels higher than 8.5 and 9.0 are required for a CSTR with and without cell washout, respectively. For a CSTR without cell washout at pH 7 and 1 mg O2/L, it was predicted that a nitrite accumulation less than 5% could be reached. Conversely, for a partially submerged continuous RDR without any additional aeration supply (already at pH 7 and 1.3 mg O2/L), high nitrite accumulation (more than 75%) was achieved and the influence of pH from 7 to 9 was not significant. This difference is believed to be caused by mass transfer. In addition, nitrification was observed to occur under oxygen transport limitation for a totally submerged continuous RDR.

Bioreactors↗

PubMed1997

Experimental studies of methemoglobinemia due to percutaneous absorption of sodium nitrite.

OBJECTIVE: Methemoglobin formation caused by a liniment solution containing sodium nitrite (30 g/L and 140 g/L) was studied in rats with normal or abraded skin, by measuring the methemoglobin concentration before and after application of liniment solutions with differing nitrite concentration. METHODS: Each liniment solution (120 microL) was applied. Methemoglobin was measured for 180 minutes using a hemoximeter. Simultaneously, arterial blood pressure and cutaneous blood flow was measured by laser Doppler flowmetry and a pressure transducer. RESULTS: After the application of each liniment solution to normal skin, the methemoglobin concentration was not significantly modified depending on the time after application. Application of liniment solution to abraded skin (140 g/L) resulted in a marked increase in methemoglobin concentration. A remarkable decrease in arterial blood pressure and subcutaneous blood flow were observed after application of liniment solution to abraded skin (140 g/L). CONCLUSIONS: Each of these findings are characteristic of nitrite and they imply the percutaneous absorption of nitrite. Regardless of the nitrite concentration, the methemoglobin concentration was consistently higher in abraded skin than in normal skin.

Administration, Cutaneous↗

PubMedDate not supplied

Hepatopulmonary syndrome induced by common bile duct ligation in a rabbit model: correlation between pulmonary vascular dilatation on thin-section CT and angiography and serum nitrite concentration or endothelial nitric oxide synthase (eNOS)1 expression.

OBJECTIVE: To investigate the correlation between radiologic vascular dilatation and serum nitrite concentration and eNOS expression in the endothelial cell and pneumocyte in a rabbit model of hepatopulmonary syndrome induced by common bile duct ligation (CBDL). MATERIALS AND METHODS: Thin-section CT scans of the lung and pulmonary angiography were obtained 3 weeks after CBDL (n = 6), or a sham operation (n = 4), and intrapulmonary vasodilatation was assessed. The diameter and tortuosity of peripheral vessels in the right lower lobe by thin-section CT and angiography at the same level of the right lower lobe in all subjects were correlated to serum nitrite concentration and eNOS (endothelial nitric oxide synthase) expression as determined by immunostaining. RESULTS: The diameters of pulmonary vessels on thin-section CT were well correlated with nitrite concentrations in serum (r = 0.92, p < 0.001). Dilated pulmonary vessels were significantly correlated with an increased eNOS expression (r = 0.94, p < 0.0001), and the severity of pulmonary vessel tortuosity was found to be well correlated with serum nitrite concentration (r = 0.90, p < 0.001). CONCLUSION: The peripheral pulmonary vasculature in hepatopulmonary syndrome induced by CBLD was dilated on thin-section CT and on angiographs. Our findings suggest that peripheral pulmonary vascular dilatations are correlated with serum nitrite concentrations and pulmonary eNOS expression.

Angiography↗

PubMed2001

[Daily intakes of nitrate and nitrite in middle-aged men by the duplicate portion method].

Daily intakes of nitrate and nitrite of middle-aged men (30-59 years of age, n = 100) in Hiroshima Prefecture were estimated directly by the duplicate portion method. The daily intake of nitrate was 190.8 +/- 128.5 mg. The daily intake of nitrate/kg body weight was 2.87 +/- 2.00 mg, which is about 78% of the acceptable daily intake (ADI). The daily intake of nitrate tended to increase with increasing age. The daily intake of nitrite was 3.837 +/- 3.647 mg. The daily intake of nitrite/kg body weight was 0.057 +/- 0.050 mg, which is about 95% of the ADI. In the case of nitrite, there was no age-related difference. The proportions of men, whose daily intakes of nitrate and nitrite were above the ADI, were 27% and 34%, respectively. The proportion of men above the ADI of both nitrate and nitrite was 10%.

Adult↗

PubMed2003

Nitrite-induced injury of Listeria monocytogenes and the effect of selective versus nonselective recovery procedures on its isolation from frankfurters.

Sodium nitrite (NaNO2) is used as a curing agent in frankfurters. Although previous studies have documented the bacteriostatic abilities of NaNO2 toward Listeria monocytogenes, few if any studies have been conducted that consider the possibility of sublethal injury to L. monocytogenes by exposure to NaNO2. The goals of this study were to determine whether NaNO2 has the ability to injure L. monocytogenes, to determine whether nitrite injury is reversible, and to compare the recovery of L. monocytogenes from frankfurters containing nitrite with Listeria repair broth (LRB) and University of Vermont modified Listeria enrichment broth (UVM). NaNO2, when used at concentrations of 100 and 200 ppm, was found to injure L. monocytogenes. The injury was completely reversible, or growth of uninjured Listeria occurred in LRB when injury was between 98.5 and 98.7%. However, total recovery was not observed in LRB when injury exceeded 99%. UVM was unable to reverse the effects of nitrite-injured L. monocytogenes. With respect to time, inoculum, and meat type, LRB was found to be consistently superior to UVM at recovering L. monocytogenes from frankfurters. Nitrite injury might be a factor influencing detection and recovery of L. monocytogenes from frankfurters.

Colony Count, Microbial↗

PubMed2005

Subtilisin QK, a fibrinolytic enzyme, inhibits the exogenous nitrite and hydrogen peroxide induced protein nitration, in vitro and in vivo.

Subtilisin QK, which is newly identified as a fibrinolytic enzyme from Bacillus subtilis QK02, has the ability of preventing nitrotyrosine formation in bovine serum albumin induced by nitrite, hydrogen peroxide and hemoglobin in vitro verified by ELISA, Western-blot and spectrophotometer assay. Subtilisin QK also attenuates the fluorescence emission spectra of bovine serum albumin in the course of oxidation caused by nitrite, hydrogen peroxide and hemoglobin. Furthermore, subtilisin QK could suppress the transformation of oxy-hemoglobin to met-hemoglobin caused by sodium nitrite, but not the heat-treated subtilisn QK. Compared with some other fibrinolytic enzymes and inactivated subtilisin QK treated by phenylmethylsulfonylfluoride, the ability of inhibiting met-hemoglobin formation of subtilisin QK reveals that the anti-oxidative ability of subtilisin QK is not concerned with its fibrinolytic function. Additionally, nitrotyrosine formation in proteins from brain, heart, liver, kidney, and muscle of mice that is intramuscular injected the mixture of nitrite, hydrogen peroxide and hemoglobin is attenuated by subtilisin QK. Subtilisin QK can also protect Human umbilical vein endothelial cell (ECV-304) from the damage caused by nitrite and hydrogen peroxide.

Animals↗

PubMed1976

[Methemoglobinemias caused by ingestion of nitrites and nitrates].

Nitrites and nitrates are often responsible for methemoglobinemy. Infants, on account of their greater sensibility to oxidizing agents, are particularly liable to poison by nitrates and nitrites. Sodium nitrite can be responsible for poisoning after accidental ingestion or owing to an overdose when preparing salt provisions, or because it has been mistaken for another product. Then it is often a case of collective poisoning. Nitrates generally produce methenoglobinemy when they are changed into nitrites under the influence of a bacterial proliferation or of a reductase held in plants. It happens with spinach and carrot soup. Nitrates can pollute municipal water supply and chiefly well water. As regards therapy, cases of methemoglobinemy have been noted after an overdose of potassium nitrate and especially of bismuth subnitrate. The treatment of methemoglobinemy caused by nitrates and nitrites is not specific: suppression of the oxidizing agents, oxygenation, prescription of reducing agents.

Adult↗

PubMed1976

[Various toxic effects of nitrates and nitrites].

The main features of the long-term toxicity of nitrates and/or nitrites in man and experimental animals are reviewed; the possible formation of carcinogenic nitrosamines is dealt with in another paper of this series. It appears that the allowable daily intake of nitrates and nitrites for the healthy adult man has been evaluated chiefly from the no-effect levels in rats. First, the no-effect levels in rats are questionable, since some experiments have pointed out adverse effects of nitrates and nitrites with dosages near, or lower than, the so-called no-effect levels. Second, there is a risk that the allowable daily intake is outpassed in the diet of a man. Third, nutritional conditions, such as the vitamin A or C, or the iodine content of the diet, as well as other factors which are discussed, might alter theno-effect levels. From the cell metabolism viewpoint, nitrites are inhibitors of oxidative phosphorylation and of microsomal enzymes. Our present lack of knowledge does not yet allow us to explain the long-term toxicity of nitrates and nitrites in terms of cell metabolic disturbances.

Adult↗

PubMed1999

Biochemical predetermination of the NO synthase and nitrite reductase components of the nitric oxide cycle.

This review presents some aspects of a concept of cellular evolution bearing a relationship to nitrate--nitrite respiration, the endosymbiosis theory, and the origin of NO synthase and nitrite reductase activity in heme-containing proteins. Analysis of structural and functional unity of the NO synthase and nitrite reductase systems suggests that these systems did not arise without any relation to evolutionarily ancient energetic systems of cells. The use of symmetry principles reveals commonalities among many electron transport chains which in the language of physics is called "invariance". This work also comparatively analyzes the nitric oxide cycle and the known nitrogen cycle. The ideas about evolution of the NO synthase and nitrite reductase systems developed here are clearly compatible with the endosymbiotic theory and the hypothesis that nitrate--nitrite respiration was a precursor of oxygen-dependent respiration.

Biological Evolution↗

PubMed1999

Nitrite plasma levels in normolipemic and hypercholesterolemic arteriopathics after vasoactive and lipid-lowering treatment.

BACKGROUND: The authors studied the plasmatic levels of nitrites, stable end-products of nitric oxide in arteriopathic patients before and after vasoactive and lipid-lowering treatment. METHODS: The series consisted of 63 subjects (mean age 64 +/- 9) suffering from peripheral arterial occlusive disease; 21 subjects with total cholesterol (TC) lower than 200 mg/dl were considered as normolipemic (group A); 24 subjects with TC ranging between 200 and 240 mg/dl were considered as mild hypercholesterolemic (group B); 18 subjects with TC higher than 240 mg/dl were consider as severe hypercholesterolemic (group C). All the patients were examined before and after 15 and 30 days of a vasoactive treatment (calciparine, aspirin, buflomedil and pentoxiphylline); group B after vasoactive and diet (NCEP phase 1) treatment and group C after vasoactive, diet and drug (simvastatin) treatment. Nitrite plasma levels were determined by the Gutman and Hollywood colorimetric method. RESULTS: In group A the basal value of nitrites was sharply (p < 0.05) lower than controls; after vasoactive treatment a significant increase (p < 0.05), was observed after 15 and 30 days; in group B the basal value was higher than controls; after 15 days a significant increase (p < 0.5) was noted, but a regression was found after 30 days. Also in group C the basal value of nitrites was higher (p < 0.05) than controls; after treatment significant changes were not found. CONCLUSIONS: The increase of nitrites in group A may be due to an improved endothelial function; this phenomenon, less appreciable in group B and no longer evident in group C may depend on the lipid-lowering treatment.

Aged↗

PubMed1999

[The evaluation of nitrate and nitrite contents in diets of preschool children].

The contents of nitrites and nitrates in whole day's food of children at preschool age have been examined. Meals consisted of three dishes were taken from one of the day nurseries in Lódź in January 1996. In the evaluation of the degree of exposure the highest permissible daily intake was considered of nitrites (0.2 mg NaNO2) and nitrates (5 mg KNO3) for kg of body weight and assumed average body weight was 20 kg for children. The contents of nitrites and nitrates were determined spectrophotometrically on the basis of Griess reaction. Nitrates were reduced to nitrites passing anaquelos extract of the studied sample through a column filled with cadium dust. The range of quality of collected nitrates in meals in wide and the quantity oscillate between 8.9 and 127, mg KNO3, the average quantity is 55.01 mg KNO3. The quantity of collected nitrites is between 0.5 and 3.8 mg NaNO2 and the average quantity is 1.58 mg NaNO2.

Child↗

PubMed1999

[The evaluation of nitrates and nitrites in daily food intake of adults].

During the research work the contents of nitrates and nitrites in whole day's food of adults were examined. The study were carried out in February 1996. In the evaluation of the degree of exposure highest permissible daily intake was considered of nitrites (0.2 mg NaNO2) and nitrates (5 mg KNO3) for one kg of body weight, and the assumed average body weight was 60 kg for adults. The contents of nitrites and nitrates were determined spectrophotometrically of the basis of Griess reaction. Nitrate was determined colorimetrically using sulphanic acid and N-1-naphtyl-ethylene-diamine. The quantity of collected nitrates and nitrites in whole day's food oscillates between 69.5 and 737.5 mg KNO3 and the average quantity is 304.55 mg KNO3. The quantity of collected nitrites is in the average 1.8-8.4 mg NaNO2, and the average quantity is 4.39 mg NaNO2.

Adult↗

PubMedDate not supplied

Sensitive spectrophotometric determination of nitrite in human saliva and rain water and of nitrogen dioxide in the atmosphere.

A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054-0.816 microg/mL. The molar absorptivity of the colored compound is 4.61 x 10(4) L/mol x cm). The detection limit is 12.1 microg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 microg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 microg/mL).

Air Pollutants↗

PubMed1975

Filter paper as a source of error in the determination of nitrite in meat.

Samples of filter paper were found which contain sufficient nitrite to cause significant error in determining the nitrite content of cured meat products by the official AOAC method. Six of 28 boxes of filter paper examined were contaminated with nitrite. All 6 contaminated boxes were the same brand and grade. These samples of filter paper could contribute from 4.6 to 18.4 ppm nitrite to the amount of nitrite analyzed for in meat.

Filtration↗