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PubMed1979

Death associated with nitrite ingestion: report of a case.

The tissue concentrations of nitrite and nitrate found at autopsy of a case of intentional ingestion of nitrite salts have been reported. The percentage of methemoglobin and the serum nitrite concentrations are consistent with those reported for acute overdoses. We conclude that noth nitrite and nitrate salts may be identified in tissues from persons ingesting only nitrite salts and that a significant conversion to nitrate may result from oxidation of nitrite during the conversion of heme iron to Fe3+.

Adult↗

PubMed1984

Animal feeding study with nitrite-treated meat.

In order to detect possible formation of carcinogenic N-nitroso compounds from nitrite and nitrosatable compounds in meat, studies were carried out with 70 male and 140 female F0 rats, divided into six groups, and 60, 100, 70, 60, 60 and 66 of their male and female offspring. One control group received casein and other groups chopped pork as the sole protein source (45%, mass/mass) on a fresh basis, either salted (sodium chloride) or not. For test groups, nitrite was also added to the meat before autoclaving and storing the diet and represented mass fractions of 200, 1 000 and 4 000 mg/kg, as sodium nitrite. The results do not demonstrate any effect on reproduction and no significant carcinogenic effect was revealed. However, an observed tendency toward an increased number of tumour-bearing rats in the highest dose group, plus the possible formation of carcinogenic N-nitroso compounds in nitrite-treated meat products, led to a recommendation to reduce the use of nitrite. Results from a concomitant study demonstrate that it is possible to produce many cured-meat products with the addition of only 50 mg/kg nitrite.

Animal Feed↗

PubMed1984

Formation of nitrite in gastric juice of patients with various gastric disorders after ingestion of a standard dose of nitrate--a possible risk factor in gastric carcinogenesis.

Samples of fasting gastric juice (12-h fasting period) from patients with various upper gastrointestinal complaints and from healthy controls were collected by aspiration immediately before and 30, 90, and 240 min after ingestion of 200 mg nitrate in water. Nitrite concentration in the gastric juice of healthy controls remained essentially in a low concentration range throughout the whole sampling period (median values at various time points, 0.1-1.7 mg/L). Patients with gastric and duodenal ulcers and patients who had undergone proximal-gastral vagotomy did not show significant increases in gastric nitrite at any time when compared with healthy controls, using the Wilcoxon rank sum test. Patients with chronic atrophic gastritis and those who had undergone Billroth I or Billroth II gastric resection, however, showed significant increases in gastric nitrite, sometimes with high individual peaks: 80 mg/L in one patient with chronic atrophic gastritis, 50 mg/L in a Billroth I patient and 200 mg/L in a Billroth II patient. The results show that patients with chronic atrophic gastritis and patients who have undergone Billroth I and Billroth II gastrotomy not only have higher basal nitrite values in their gastric juice (12-h fasting) but also react with significantly higher increases in gastric nitrite to an oral dose of 200 mg nitrate, compared with healthy controls, ulcer patients and patients who have undergone proximal-gastral vagotomy. Higher nitrite levels might lead to an enhanced intragastric formation of N-nitroso compounds, and this might be relevant to the increased gastric cancer risk of these groups of patients.

Duodenal Ulcer↗

PubMed1983

[Endogenous synthesis of carcinogenic N-nitroso compounds: bacterial flora and nitrite formation in the healthy human stomach].

The endogenous synthesis of cancerogenic N-nitroso compounds: Bacterial flora and nitrite formation in the human stomach. In the discussion of the endogenous nitrosamine synthesis, nitrites play a decisive role. Since in a healthy stomach the acidity important for the nitrosamine formation is present, but since this acid environment is hostile to the bacterial growth and thus counteracts bacterial endogenous nitrite formation, the oral cavity has so far been regarded as the main site of endogenous nitrite formation. An analysis of 130 gastric secretions taken from empty stomachs has demonstrated that also in a healthy stomach considerable germ counts may be obtained in part when acidity is lowered physiologically (e.g. at night). Nitrite concentrations, which are six times as high as the quantities supplied with the saliva at the same time, are also produced in the acid pH range from 4 to 6. Consequently, in a healthy stomach as well the quantity of nitrite available for an endogenous nitrosamine synthesis is by far higher than has been assumed previously. This physiological risk should be allowed for in evaluating the pathophysiological or therapeutic changes in the gastric environment.

Bacteria↗

PubMed1980

[Effect of sample storage conditions and treatment on "free nitrite" in meat products].

The aim of the work presented here is to study the effect of different factors on the amount of "free" nitrite in meat products. Two kinds of factors are involved: --factors modifying the amount of "free" nitrite in the product; --factors modifying the amount of nitrite determined as "free". The former are mainly depending on the storage conditions of the products, for instance: low pH, light exposure, high temperature, increase the nitrite losses. The latter are depending on the analysis methodology. A strong physical treatment of the samples, a high temperature during extraction, a long time of extraction, the repetition of the extraction, increase the amount of nitrite determined as "free" by releasing a part of the bound fraction. So, it is very important, for the significance of results in "free" nitrite determination, to know very precisely storage and treatment conditions of the samples.

Animals↗

PubMed1998

[Studies for measuring nitrates and nitrites in food served to patients in hospitals from the province of Białystok].

The aim of this study was determination of daily level intake of nitrates and nitrites in the individual meals in the daily food rations of patients from the hospitals from the province of Białystok. The studied material were meals and total diets, with regard to selected food products, which were taken to preparing the dishes. The investigation materials were taken from February to June 1996. Analysis of nitrates and nitrites contents was realized by the commonly method based on the reaction of Griess. Nitrate was reduced to nitrite on a cadmium column whereupon, it was determined colorimetrically. The daily dose of nitrates for patients of 70 kg weight to the level on 350 mg KNO3/person and nitrites on 14 mg NaNO2/person, was established according to the Expert Committee FAO/WHO recommendations that acceptable daily intake level of nitrates on 5 mg and nitrites--0.2 mg to 1 kg body weight. In the light of these investigations it was found that main nitrates source in daily food rations were dinners containing red beet, while the great amount of nitrates was supplied in breakfasts and suppers with rennet maturing cheeses and sausages. From among all evaluated daily diets, 1/3 exceeded the admissible daily intake levels of nitrates and nitrites.

Animals↗

PubMed2002

Optimum conditions for effective use of the terminating ion in transient isotachophoresis for capillary zone electrophoretic determination of nitrite and nitrate in seawater, with artificial seawater as background electrolyte.

We have examined transient isotachophoresis (ITP) conditions, e.g. the nature of the terminating ion, its concentration, and the injection procedure, to improve the limit of detection (LOD) for determination of nitrite and nitrate in seawater by capillary zone electrophoresis (CZE). Artificial seawater containing 3.0 mmol L(-1) cetyltrimethylammonium chloride (CTAC) was used as background electrolyte (BGE). After sample injection 600 mmol L(-1) acetate was separately injected into the capillary as the terminating ion for transient ITP. The LOD for nitrite and nitrate, obtained at a signal-to-noise ratio (S/N) of 3, were 15 and 7.0 microg L(-1) (as nitrogen), respectively. Relative standard deviations (RSD) of peak area for nitrite and nitrate were 7.3 and 0.8%, respectively, and the RSD of peak height were 5.7 and 1.2%, respectively, when the concentrations of nitrite and nitrate were 0.05 and 0.25 mg L(-1). The RSD of migration time for these ions was 0.2%. The proposed method was applied to the determination of nitrite and nitrate in seawater samples. The results for nitrite were nearly in agreement with those obtained by naphthylethylenediamine spectrophotometric analysis (SPA; correlation coefficient 0.9041).

Journal Article↗

PubMed2003

Effects of shock wave lithotripsy on plasma and urinary levels of nitrite and adrenomedullin.

PURPOSE: In this prospective clinical study, we aimed to determine whether shockwave lithotripsy (SWL) has any specific effect on plasma as well as urinary nitrite, a stabile metabolite of nitric oxide (NO) and adrenomedullin (AM) concentrations, and to investigate whether these variables can be used as a marker for detecting shockwave-induced impairment of renal tubular and glomerular cells. MATERIAL AND METHODS: A total of 20 patients with renal pelvic or caliceal stones < or =2 cm undergoing anesthesia-free SWL without auxiliary measures and a control group of ten patients without any urological symptoms were included in this study. The plasma and urinary concentrations of nitrite and AM were measured before, 24 h, and 7 days after SWL. Nitrite levels were measured by Griess reaction. Reverse-phase high-performance liquid chromatography (HPLC) was used to determine AM levels. RESULTS: Application of high-energy shock waves (HESW) in our study caused a statistically significant increase in plasma levels of both NO and AM, which reflected an organized response of the kidney to this type of trauma in an attempt to maintain normal renal hemodynamics. Mean plasma nitrite concentration before SWL application was 29.9+/-7.6 micromol/l and this value was found to be 39.02+/-8.45 micromol/l at 24-h follow-up. Comparative evaluation of the plasma concentrations of AM revealed a significant increase at the 24-h examination: 20.51+/-3.0 pmol/ml and 32.54+/-4.3 pmol/l, respectively. On the other hand, comparative evaluation of urinary levels of both nitrite and AM levels before as well as 24 h after SWL application revealed a statistically significant increase related to markers. CONCLUSION: This first clinical study on plasma-urinary nitrite and AM levels in patients undergoing the SWL procedure indicated that plasma and urine levels of both peptides were increased. Our findings in turn suggested that SWL application to kidney can stimulate the NO-cGMP signalling pathway to increase NO production in the kidney. Our findings also indicated that the increased levels of NO and AM secretion during renal parenchymal ischemia may be protective enough for renal pathological alterations resulting from SWL-induced renal trauma. We suggest that this increase may be a compensatory response to SWL induced injury.

Adrenomedullin↗

PubMed1989

Determination of nitrite in drinking water and environmental samples by ion exclusion chromatography with electrochemical detection.

An extremely sensitive determination of nitrite in drinking water (tap water and underground water) and environmental samples (rain, lake water, and soil) was achieved by ion exclusion chromatography (IEC) with electrochemical (EC) detection. Potential interferences in the determination of nitrite by the standard spectrophotometric method or by the ion exchange chromatographic method with either conductivity detection or UV detection were eliminated. The detection limit was 0.1 ppb without preconcentration. No nitrite was observed from tap water or underground drinking water. The recoveries of nitrite added to tap water at 0.02, 0.1, and 1 ppm levels were between 96 and 104.5%. The average coefficient of variation was 4.7%. The recovery results were in good agreement with those obtained by the standard spectrophotometric method. Nitrite concentrations between 0.068 and 0.19 ppm were observed in rain within a week period. A greater variation, between 0.015 and 0.26 ppm, was observed in lake water. Amounts of 19.1 ppm and 0.50 ppm nitrite were observed from fertilized and unfertilized soil, respectively.

Chromatography, Liquid↗

PubMed2003

Kinetics and mechanism of the cobalt phthalocyanine catalyzed reduction of nitrite and nitrate by dithionite in aqueous solution.

The reaction of sodium nitrite with sodium dithionite was studied in the presence of cobalt(II) tetrasulfophthalocyanine, COII(TSPc)4-, in aqueous alkaline solution. The overall mechanism comprises the reduction of CoII(TSPc)4- by dithionite, followed by the formation of an intermediate complex between COI(TSPc)5- and nitrite, which undergoes two parallel subsequent reactions with and without nitrite as a reagent. Kinetic parameters for the different reaction steps of the catalytic process were determined. The final product of the reaction was found to be ammonia. Contrary to those found for the catalytic reduction of nitrite, the products of the catalytic reduction of nitrate were found to be dinitrogen and nitrous oxide. The possible catalytic reduction of nitrous oxide was confirmed by independent experiments. The striking differences in the reduction products of nitrite and nitrate are explained in terms of different structures of the intermediate complex between CoI(TSPc)5- and substrate, in which nitrite and nitrate are suggested to coordinate via nitrogen and oxygen, respectively.

Journal Article↗

PubMed1996

Selective Oxygen Transfers with Iron(III) Porphyrin Nitrite.

The reaction of octaethylporphyrin iron(III) chloride with potassium crown ether (18-crown-6) nitrite in N-methylpyrrolidone-1% acetic acid under argon generates the iron(III) nitrite salt (PFeNO(2)). The latter is a unique and selective oxygen atom transfer reagent. The reaction of a broad range of substrates (S) proceeds quantitatively to yield the oxidized substrate and the iron(II) porphyrin-nitrosyl adduct: PFeNO(2) + S --> PFeNO + SO. Diatomic molecules to which oxygen is directly transferred from PFeNO(2) are NO, CO, and O(2). The conversion NO to NO(2) is shown via (15)NO(2)(-) labeling experiments to proceed exclusively by the O atom transfer process. The ozone, generated from dioxygen, was trapped with nitrite ion and the two olefins 2-methyl-2 butene and 2,3-dimethyl-2 butene. These substances are inert to PFeNO(2) under argon. However, in an oxygen-saturated reaction mixture, nitrite produced nitrate. The olefins, following reduction of the reaction mixture with Zn/HOAc, yielded 1 mol of acetone and acetaldehyde and 2 mol of acetone, respectively. Other simple O atom transfers under argon were observed with dimethyl sulfide and triphenylphosphine. The PFeNO(2) reagent shows a preference for O insertion into allylic, benzylic, and aldehydic C-H bonds. Thus, no olefin containing these moieties is epoxidized. However, styrene and cis-stilbene are converted to styrene oxide and cis-stilbene oxide, respectively. The double oxidation of allylbenzene to trans-cinnamaldehyde entails an allylic rearrangement that suggests radical character to the O insertion process. However, no kinetic evidence for this was obtained. The reaction is an overall third-order process, rate = k(PFe(III))(NO(2)(-))(S). There was no correlation of observed rates with relevant C-H bond dissociation energies of substrates. The fastest reacting substrate was nitric oxide (k(22) degrees = 52 M(-)(2) s(-)(1)) and the slowest was toluene (k(50) degrees = 6.3 x 10(-)(4) M(-)(2) s(-)(1)). The range and selectivity of these O atom transfers sets them apart from the catalytic oxidations brought about by reactions of iron(III) porphyrins with peroxides, iodosoaryls, hypochlorite, and other oxidants. The driving force for the relatively mild oxidations with PFeNO(2) resides in the thermodynamic stability of the heme-NO adduct. Given the broad presence of nitrite in the environment and the ubiquity of porphyrins in the biosphere, the activation of nitrite by iron porphyrins has both an environmental and biochemical significance.

Journal Article↗

PubMed2007

Conformers and photochemistry of propyl nitrites: a matrix isolation study.

The infrared spectra of both constitutional isomers (n and i) of propyl nitrite have been recorded in an Ar matrix. Conformational analysis and assignments of the vibrational transitions have been carried out on the basis of quantum chemical calculations. Assignment of spectral lines to different conformers was also aided experimentally, by utilizing the different rate of photodecomposition of the conformers, as well as by employing conformational cooling using a supersonic jet as the inlet source for matrix deposition. The rate of photodecomposition is primarily determined by the steric alignment of the nitrite group, whereas jet cooling affects mainly the conformation of the alkyl tail. On the basis of these experimental observations and computational predictions two to three conformers of isopropyl nitrite and eight conformers of n-propyl nitrite were identified. After broadband ultraviolet-visible (UV-vis) photolysis of isopropyl nitrite in the matrix, HNO, acetone, HNO.acetone complex, acetaldehyde, and nitrosomethane were identified as the main products. Furthermore, in a small amount, NO and possibly the isopropoxy radical were also present in the matrix. Photolysis of n-propyl nitrite yielded HNO, propanal, and their 1:1 complex as the main products together with a small amount of NO and cis-1-nitrosopropanol.

Journal Article↗

PubMed1966

Hydrogenase mediated nitrite reduction in chlorella.

The assay of the hydrogenase of glucose-grown cells of Chlorella pyrenoidosa, strain 7-11-05 by means of nitrite reduction with molecular hydrogen is described. The hydrogenase of Chlorella shows maximum activity immediately after equilibration in the hydrogen atmosphere. The hydrogenase mediated reduction of nitrite to ammonia requires the presence of CO(2). However, at pH 6.4. when the reaction proceeds optimally, there is apparently sufficient retention of metabolic CO(2) to support the reaction, which goes to completion, at near maximum rates.Reduction of nitrite in the hydrogenase system when CO(2) is present results in the uptake of 3 moles of H(2) per mole of nitrite and ammonia is the product. When CO(2) is absent or limiting, ammonia is also formed from nitrite but with the uptake of less than the stoichiometric amount of H(2). It is concluded that CO(2) is essential for the uptake of H(2), and that in the absence of CO(2) internal hydrogen donors support nitrite reduction.The possibility that CO(2) exerts a catalytic effect in all reductions mediated by hydrogenase in algae is considered, and a further hypothesis, that hydrogenase arises from that portion of the photosynthetic machinery which also shows a catalytic requirement for CO(2), is proposed.

Journal Article↗

PubMed1983

Nitrate and Nitrite Reduction in Relation to Nitrogenase Activity in Soybean Nodules and Rhizobium japonicum Bacteroids.

Soybean (Glycine max L. cv Williams) seeds were sown in pots containing a 1:1 perlite-vermiculite mixture and grown under greenhouse conditions. Nodules were initiated with a nitrate reductase expressing strain of Rhizobium japonicum, USDA 110, or with nitrate reductase nonexpressing mutants (NR(-) 108, NR(-) 303) derived from USDA 110. Nodules initiated with either type of strain were normal in appearance and demonstrated nitrogenase activity (acetylene reduction). The in vivo nitrate reductase activity of N(2)-grown nodules initiated with nitrate reductase-negative mutant strains was less than 10% of the activity shown by nodules initiated with the wild-type strain. Regardless of the bacterial strain used for inoculation, the nodule cytosol and the cell-free extracts of the leaves contained both nitrate reductase and nitrite reductase activities. The wild-type bacteroids contained nitrate reductase but not nitrite reductase activity while the bacteroids of strains NR(-) 108 and NR(-) 303 contained neither nitrate reductase nor nitrite reductase activities.Addition of 20 millimolar KNO(3) to bacteroids of the wild-type strain caused a decrease in nitrogenase activity by more than 50%, but the nitrate reductase-negative strains were insensitive to nitrate. The nitrogenase activity of detached nodules initiated with the nitrate reductase-negative mutant strains was less affected by the KNO(3) treatment as compared to the wild-type strain; however, the results were less conclusive than those obtained with the isolated bacteroids.The addition of either KNO(3) or KNO(2) to detached nodules (wild type) suspended in a semisolid agar nutrient medium caused an inhibition of nitrogenase activity of 50% and 65% as compared to the minus N controls, and provided direct evidence for a localized effect of nitrate and nitrite at the nodule level. Addition of 0.1 millimolar sucrose stimulated nitrogenase activity in the presence or absence of nitrate or nitrite. The sucrose treatment also helped to decrease the level of nitrite accumulated within the nodules.

Journal Article↗

PubMed1988

Action spectra for nitrate and nitrite assimilation in blue-green algae.

Action spectra for the assimilation of nitrate and nitrite have been obtained for several blue-green algae (cyanobacteria) with different accessory pigment composition. The action spectra for both nitrate and nitrite utilization by nitrate-grown Anacystis nidulans L-1402-1 cells exhibited a clear peak at about 620 nanometers, corresponding to photosystem II (PSII) C-phycocyanin absorption, the contribution of chlorophyll a (Chl a) being barely detectable. The action spectrum for nitrate reduction by a nitrite reductase mutant of A. nidulans R2 was very similar. All these action spectra resemble the fluorescence excitation spectrum of cell suspensions of the microalgae monitored at 685 nanometers-the fluorescence band of Chl a in PSII. In contrast, the action spectrum for nitrite utilization by nitrogen-starved A. nidulans cells, which are depleted of C-phycocyanin, showed a maximum near 680 nanometers, attributable to Chl a absorption. The action spectrum for nitrite utilization by Calothrix sp. PCC 7601 cells, which contain both C-phycoerythrin and C-phycocyanin as PSII accessory pigments, presented a plateau in the region from 550 to 630 nanometers. In this case, there was also a clear parallelism between the action spectrum and the fluorescence excitation spectrum, which showed two overlapped peaks with maxima at 562 and 633 nanometers. The correlation observed between the action spectra for both nitrate and nitrite assimilation and the light-harvesting pigment content of the blue-green algae studied strongly suggests that phycobiliproteins perform a direct and active role in these photosynthetic processes.

Journal Article↗

PubMed1991

Blue Light, a Positive Switch Signal for Nitrate and Nitrite Uptake by the Green Alga Monoraphidium braunii.

Blue light was shown to regulate the utilization of oxidized nitrogen sources by green algae, both by activating nitrate reductase and promoting nitrite reductase biosysnthesis (MA Quiñones, PJ Aparicio [1990] Inorganic Nitrogen in Plants and Microorganisms, Springer-Verlag, Berlin, pp 171-177; MA Quiñones, PJ Aparicio [1990] Photochem Photobiol 51: 681-692). The data reported herein show that, when cells of Monoraphidium braunii at pH 8, containing both active nitrate reductase and nitrite reductase, were sparged with CO(2)-free air and irradiated with strong background red light, they took up oxidized nitrogen sources only when PAR comprised blue light. The activation of the transport system(s) of either both nitrate and nitrite was very quick and elicited by low irradiance blue light. In fact, blue light appears to act as a switch signal from the environment, since the uptake of these anions immediately ceased when this radiation was turned off. The requirement of blue light for nitrate uptake was independent of the availability of CO(2) to cells. However, cells under high CO(2) tensions, although they showed an absolute blue light requirement to initially establish the uptake of nitrite, as they gained carbon skeletons to allocate ammonia, gradually increased their nitrite uptake rates in the subsequent red light intervals. Under CO(2)-free atmosphere, cells irradiated with strong background red light of 660 nanometers only evolved oxygen when they were additionally irradiated with low irradiance blue light and either nitrate or nitrite was present in the media to provide electron acceptors for the photosynthetic reaction.

Journal Article↗

PubMed1984

Synthesis of wheat leaf nitrite reductase de novo following induction with nitrate and light.

Nitrite reductase has been purified almost 3000-fold, in 35% yield, to a specific activity of 77 units (mg protein)-1 from wheat leaves using a multi-step procedure with affinity chromatography on ferredoxin-Sepharose as the final step. The purified enzyme, although not homogeneous, exhibited absorption maxima at 278, 390, 568 and 687 nm. Minor contaminants were removed by gel filtration in the presence of sodium dodecyl sulphate to yield a single polypeptide of Mr 60 500 as judged by polyacrylamide gel electrophoresis. Antibodies raised against this polypeptide were shown to cross-react with native nitrite reductase and were used to study the synthesis of nitrite reductase in vivo and in vitro. The increase in nitrite reductase activity following exposure of dark-grown plants to nitrate and light was shown by immunodecoration of Western blots to be due to synthesis de novo. Poly(A)-rich RNA isolated from plants actively synthesising nitrite reductase was shown to direct the synthesis in a rabbit reticulocyte lysate of a polypeptide of Mr 64000 which was immunoprecipitated by antibodies to nitrite reductase.

Cell-Free System↗

PubMed2004

Fluorometric determination of sulfite and nitrite in aqueous samples using a novel detection unit of a microfluidic device.

On-chip fluorescence determination of sulfite and nitrite with N-(9-acridinyl)maleimide (NAM) and 2,3-diaminonaphthalene (DAN) has been developed using a novel fluorescence detection unit for microchip analysis. Usually, these fluorescence reagents are derivatized and detected separately in microchip analysis because different fluorescence wavelengths are emitted. The proposed fluorescence detection unit has optical fibers with no optical filter, and plural wavelengths of fluorescence were detected sensitively, even in the microchip. In this study, the simultaneous determination of sulfite and nitrite in environmental samples was performed with a polymer microchip analysis system. The calibration curves of sulfite and nitrite showed linear relations (R2 = 0.998 (sulfite) and R2 = 0.990 (nitrite)), and the relative standard deviations (RSD) for 4 runs were 2.1% (20 microM sulfite) and 1.3% (20 microM nitrite), respectively. The proposed method was applied to the recovery test of sulfite and nitrite in environmental samples.

Journal Article↗