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PubMed1976

[Effect of nitrites and nitrates on various aspects of vitamin nutritional status].

Nitrites--and sometimes nitrates--decrease the biological availability of dietary vitamins in several animal species. 1. Numerous studies show that ingested nitrites decrease the stock of liver vitamin A in nonruminants (Rat, Pig, Chicken); the effect of nitrates is less pronounced even lacking. In vitro, experiments allow to think that vitamin A and beta-carotene can be destroyed by nitrites in the diet and/or in the gastrointestinal tract. 2. Some recent works--those of Lhuissier particularly--show that nitrites can affect some vitamins of B group and their metabolism. Thiamine and vitamin B6 contents of several tissues decrease when nitrites are fed to the Rat. In the case of thiamine, the result could be partially explained by destruction of the vitamin in the diet and may be in the gastrointestinal tract. No such explanation seems to be possible in the case of vitamin B6.

Animals↗

PubMed1979

Identification of the iron-sulfur center of spinach ferredoxin-nitrite reductase as a tetranuclear center, and preliminary EPR studies of mechanism.

EPR spectroscopic and chemical analyses of spinach nitrite reductase show that the enzyme contains one reducible iron-sulfur center, and one site for binding either cyanide or nitrite, per siroheme. The heme is nearly all in the high spin ferric state in the enzyme as isolated. The extinction coefficient of the enzyme has been revised to E386 = 7.6 X 10(4) cm-1 (M heme)-1. The iron-sulfur center is reduced with difficulty by agents such as reduced methyl viologen (equilibrated with 1 atm of H2 at pH 7.7 in the presence of hydrogenase) or dithionite. Complexation of the enzyme with CO (a known ligand for nitrite reductase heme) markedly increases the reducibility of the iron-sulfur center. New chemical analyses and reinterpretation of previous data show that the enzyme contains 6 mol of iron and 4 mol of acid-labile S2-/mol of siroheme. The EPR spectrum of reduced nitrite reductase in 80% dimethyl sulfoxide establishes clearly that the enzyme contains a tetranuclear iron-sulfur (Fe4S4) center. The ferriheme and Fe4S4 centers are reduced at similar rates (k = 3 to 4 s-1) by dithionite. The dithionite-reduced Fe4S4 center is rapidly (k = 100 s-1) reoxidized by nitrite. These results indicate a role for the Fe4S4 center in catalysis.

Dithionite↗

PubMed1985

Denitrification of high concentrations of nitrites and nitrates in synthetic medium with different sources of organic carbon. III. Methanol.

The denitrification of nitrites and nitrates (1000 mg N/l) in medium containing methanol as a source of organic carbon was studied. Continuous cultures of mixed population of autochtonic microflora from bottom sludge of nitrogenous wastewater reservoir were set up in a chemostat-type column and packed bed reactor. The efficiency of denitrification of nitrates in packed bed reactor was 506.7 mg N/l/h whereas denitrification of nitrites was from 8.7 to 16.0 mg N/l/h depending on the granulation of the filing material. In the latter case 83% nitrogen was removed from the medium. One of the factors causing low efficiency of denitrification of nitrites is excessive alkalization of the medium in the bed. The use of a three-step bed with adjusted pH resulted in complete denitrification of nitrites with efficiency 60 mg N/l/h. The bacteria inside the bed were dominated by Paracoccus denitrificans and by Pseudomonas aeruginosa when nitrates were present. The sensitivity of P. denitrificans to high concentrations of nitrites seems to be the second factor contributing to low efficiency of denitrification with methanol as organic substrate.

Culture Media↗

PubMedDate not supplied

[Contamination of human milk with nitrates and nitrites].

Human milk nitrates and nitrites were assayed colorimetrically. Colostrum samples were collected on the 3rd postpartum day from 59 women inhabiting Puławy region and being potentially exposed to nitrogen compounds emitted from the industrial sources. Thirty five Lublin inhabitants serving as a control group were matched in age, parity and duration of pregnancy. Geometric mean value of nitrates and nitrites concentration in the human milk being 2.83 mg/L and 0.46 mg/L, respectively were higher in the examined group than those in the control group /2.76 mg/L and 0.32 mg/L/ but difference was statistically insignificant. Ratio of nitrates and nitrites in the examined samples was 7.38 on the average and the concentration of those compounds was related statistically significantly /p less than 0.001/. The average daily intake of nitrates and nitrites by the breast-fed neonates was 0.12 mg/kg body weight and 0.02 mg/kg body weight, respectively. These values did not exceed corresponding ADI recommended by the Joint Expert Committee of FAO/WHO in none case. Significantly positive correlation of examined mothers' age and parity with nitrates content in their colostrum was seen. In view of the obtained results is may be assumed that the examined colostrum samples contain low amounts of both nitrates and nitrites.

Breast Feeding↗

PubMed1989

[Nitrate and nitrite in the urine, saliva and blood of urologic patients].

Nitrate and nitrite contents were determined in urine, saliva, and blood of 298 patients suffering from urological diseases. Crude values of nitrate and nitrite in morning urine without any correction due to density and creatinine are sufficient for epidemiological purposes. Significant correlations exist with vegetables intake and bacteriuria, but not with age, sex, disease, smoking, and medicaments. Neither nitrate nor nitrite may be considered to be general indicators of inflammatory processes in the urogenital tract. According to recent investigations nitrite formation during bacterial infections must be seen in connection with simultaneously occurring macrophage activation, as the latter one is catalyzing the formation of carcinogenic N-nitroso compounds from nitrite and secondary amines.

Escherichia coli Infections↗

PubMed1989

Nitric oxide and nitrous oxide production and cycling during dissimilatory nitrite reduction by Pseudomonas perfectomarina.

The denitrifier Pseudomonas perfectomarina reduced nitrite under conditions of kinetic competition between cells and gas sparging for extracellular dissolved nitric and nitrous oxides, NOaq and N2Oaq, in a chemically defined marine medium. Time courses of nitrite reduction and NOg and N2Og alpha removal were integrated to give NOg and N2Og yields. At high sparging rates, the NOg yield was greater than 50% of nitrite-N reduced, and the yield of NOg + N2Og was approximately 75%. Hence interrupted denitrification yields NOaq and N2Oaq as major products. The yields varied with sparging rates in agreement with a quantitative model of denitrification (Betlach, M. P., and Tiedje, J.M. (1981) Appl. Environ. Microbiol. 42, 1074-1084) that applies simplified Michaelis-Menten kinetics to NO2-----NOaq----N2Oaq----N2. The fit gave an estimate of the maximum scavengeable NOaq yield of 73 +/- 8% of nitrite-N. Thus a minor path independent of NOaq is also required. The fit of the model to data at lower sparging rates, where normal denitrification products predominate, implies that the extracellular NOaq pool yield is independent of gas sparging rate. Thus in P. perfectomarina NOaq and N2Oaq are intermediates, or facilely equilibrate with true intermediates, during complete denitrification. The recovery of most nitrite-N as NO and/or N2O under perturbed conditions is not an artifact of irreversible product removal, but an attribute of denitrification in this species, and most probably it is characteristic of denitrification in other species as well.

Kinetics↗

PubMed1979

Gastric cancer in Colombia. IV. Nitrite and other ions in gastric contents of residents from a high-risk region.

Samples of gastric contents from 2 groups of patients from a region of high risk for gastric cancer were analyzed for pH, nitrite, nitrate, thiocyanate, and chloride. In each group, the patients could be divided into 2 subgroups: those with a gastric pH of less than 5 and those with a gastric pH of greater than 5. Above pH 5, nitrite was correlated with nitrate. The pH greater than 5 subgroups had significantly higher (P less than 0.01) nitrite content (20- to 100-fold). Some high- and low-nitrite samples were also analyzed for macro and trace metal ions, but differences were not significant. This is the first report in which patients with diagnosed gastric pathology related to a precancerous state were shown to have high levels of a putative carcinogen precursor. The results were compatible with our original hypothesis of intragastric nitrite formation by bacterial reduction of nitrate and concomitant synthesis of carcinogenic N-nitroso compounds.

Aged↗

PubMed1988

The nitrite and leukocyte esterase tests for the evaluation of asymptomatic bacteriuria in obstetric patients.

The purpose of this investigation was to compare the reliability of a urine dipstick evaluation for nitrites and leukocyte esterase activity with that of a urine culture in diagnosing asymptomatic bacteriuria in obstetric patients. A clean-catch midstream urine specimen was obtained from 750 consecutive obstetric patients presenting for initial evaluation. One portion of the specimen was tested for nitrites and leukocyte esterase activity with Chemstrip LN dipsticks. A second aliquot of urine was plated on blood and MacConkey agar and incubated aerobically. The cost of the nitrite and leukocyte esterase test was $0.35. The per patient charge for the urine cultures would have been $28. Sixty-two women (8.3%) had urine cultures of 100,000 or more colony-forming units of a uropathogen per milliliter. The sensitivities of the nitrite and leukocyte esterase test in identifying patients with positive cultures were 43 and 77%, respectively, and the specificities were 99 and 96%, respectively. The sensitivity and specificity for the two tests combined (either test abnormal) were 92 and 95%, respectively. Five patients had negative screening tests but positive urine cultures; all five isolates were gram-positive organisms, three group B streptococci and two enterococci. We conclude that neither the nitrite test nor the leukocyte esterase test alone is a sensitive enough screening test to detect asymptomatic bacteriuria in obstetric patients. The combination of the two tests, however, may provide an acceptable cost-effective alternative to screening all asymptomatic obstetric patients with urine cultures.

Bacteriuria↗

PubMed1986

Catalysis of intermolecular oxygen atom transfer by nitrite dehydrogenase of Nitrobacter agilis.

Nitrobacter agilis, which contains a very active nitrite dehydrogenase, was studied in vivo under anaerobic conditions by the 15N NMR technique. When incubated with equimolar 15NO3- and unlabeled nitrite (or 15NO2- and unlabeled nitrate) the bacterium catalyzed an isotope exchange reaction at rates about 10% those observed in the nitrite oxidase assay. When incubated with 18O-labeled 15NO2- and 18O-labeled 15NO3-, the 18O was observed to exchange at similar rates from both species into water. Finally, when incubated with equimolar [18O]nitrate and 15NO2-, intermolecular 18O transfer was observed to result in formation of double labeled nitrate and nitrite at similar rates. 18O was transferred from nitrate to a 15N species or to water at approximately equal rates under the conditions of the experiments. It is argued that the enzyme responsible for these exchange reactions is nitrite dehydrogenase and not nitrate reductase. This work and the related experiments of DiSpirito and Hooper (DiSpirito, A.A., and Hooper, A.B. (1986) J. Biol. Chem. 261, 10534-10537) represent the first demonstrations of intermolecular oxygen atom transfer among oxotransferases. Mechanistic implications are discussed.

Kinetics↗

PubMed1977

Action of Nitroglycerin and amyl nitrite in labile and essential hypertension: hemodynamic differences.

Seventeen patients with labile hypertension received nitroglycerin and 18 received amyl nitrite. Twelve patients with established essential hypertension received nitroglycerin and 12 received amyl nitrite. Nitroglycerin reduced the systolic and mean arterial pressures and cardiac output in both groups, but had no effect on diastolic pressure and total peripheral resistance. Amyl nitrite decreased systolic, diastolic, and mean arterial pressures and peripheral vascular resistance and increased heart rate and cardiac output in labile hypertensives. In established hypertensive patients, amyl nitrite decreased systolic, diastolic, and mean arterial pressures and cardiac output, and had little effect on peripheral vascular resistance. Nitroglycerin reduced arterial pressure in labile and established hypertensives through venodilation and peripheral venous pooling. Amyl nitrite and effects similar to nitroglycerin in established hypertensives; in labile hypertensives it reduced arterial pressure through arterial dilation and a decrease in peripheral vascular resistance.

Adult↗

PubMed1979

Acute toxicology of butyl nitrites and butyl alcohols.

Commercially available isobutyl nitrite (iBN), n-butyl nitrite (nBN), sec-butyl nitrite (sBN) and tert-butyl nitrite (tBN) were found to be 63%, 79%, 44% and 96% pure, respectively, by GLC analysis. Pure samples of each compound were synthesized by the action of nitrous acid on each of the corresponding butyl alcohols; GLC analysis indicated greater than 99% purity for each nitrite. In determining LD50 values (mice, i.p.) for each compound, no deaths were observed after 30 min post-administration of sBN or tBN. Gross post-mortem examination suggests the delayed lethality may be due to liver damage. Administration of isobutyl, n-butyl, sec-butyl or tert-butyl alcohols to mice produced similar hepatotoxicity, suggesting that butyl alcohols may play a role in the hepatotoxicity observed after sBN or tBN administration.

Animals↗

PubMed1980

[Effect of mercuric chloride on the analysis of nitrites in pork products].

The effect of HgCl2 on nitrite determination was studied. 0,184 mmol/l to 184 mmol/l Hg Cl2 were added during the defecation or only at the time of analysis with an autoanalyser. Hg Cl2 was added to salami, bacon, dry sausage at different time of ripening and cooked ham. An effect was noted only when Hg Cl2 was added at the defecation time. After cold water extraction, the more the added Hg Cl2, the more "titrated" nitrite. After hot extraction with water and borate, the effect of Hg Cl2 was weaker but significant. The role of Hg Cl2 was important for the accurate determination of nitrites during the ripening of some products: in 16 hours old dry sausage the effect was weak (+40%), but became large (+600%) after 2 weeks of ripening. It is proposed to use Hg Cl2 at the concentration of 4 mmol/l for the determination of total nitrites. The free nitrites should be analysed separately without Hg Cl2.

Animals↗

PubMed1982

Interaction between sample preparation techniques and three methods of nitrite determination.

Meat samples containing nitrite and varying concentrations of ascorbate, cysteine, and sodium chloride were prepared for nitrite analysis. The methods used were the AOAC method of dilution and heating; the addition of mercuric chloride, charcoal, and Carrez reagents at 2 different pH values; and direct analysis of sample supernatants with no treatment (control). The effect of these initial conditions and preparation methods on measured nitrite was determined by using 3 different Griess reagent combinations and chemiluminescent and differential pulse polarographic techniques. Systematic variations were observed in samples treated with mercuric chloride, while the addition of Carrez reagents had little or no effect. Best results were obtained by the AOAC dilution/heating method under alkaline conditions, or by charcoal addition followed by chemiluminescent or colorimetric nitrite determination. Statistical analysis of the nitrite concentrations determined in the several samples showed that these 3 procedures were precise to about 5-6% CV, which was not significantly different from the CV value of 4% determined from replicate analyses.

Indicators and Reagents↗

PubMed1978

Comparison of sample preparation procedures for colorimetric analysis of nitrite in frankfurters.

Three groups of methods for analyzing nitrite in meat are compared. All methods consist of a sequence of steps, grouped according to initial extraction procedures. In Group 1, the sample is treated with borate followed by HgCl2 or Carrez I, and then Carrez II. In Group 2, the sample is diluted with water, heated at 80 degrees C, and analyzed immediately (AOAC) or after addition of either Na2CO3 and FeCl3 or HgCl2. In Group 3, the sample is made alkaline with NH4Cl buffer and then treated with one of the following: activated carbon plus Carrez I and II, alumina cream, or AIK(SO4)2. At each step when the method involved the addition of a chemical, supernates and precipitates (if formed) were analyzed for nitrite by Griess reagent both before and after AOAC digestion. The normally discarded precipitates formed after addition of HgCl2 and Carrez I and II contained bound nitrite that could be detected by AOAC analysis. Except in the AOAC method, HgCl2 improved nitrite analysis. Results by AOAC analysis were 3 to 300% higher than those determined after addition of any chemical or combination of chemicals. Spiked meat samples could not be used in comparing nitrite analysis methods because results were misleading. Acid meat samples, such as fermented sausages, required neutralization before AOAC analysis.

Animals↗

PubMed1995

The production of nitrating species by the reaction between nitrite and hypochlorous acid.

Nitrite inhibited the killing of Escherichia coli by hypochlorous acid. The protection curve was sigmoid. Complete protection occurred at nitrite concentrations greater than that of hypochlorous acid. Hypochlorous acid reacts rapidly with nitrite, as shown by phenolic nitration, using 4-hydroxyphenylacetic acid. The nitration was biphasic. Amines and amino acids inhibited the nitration, but metal chelators and hydroxyl radical scavengers except for dimethylsulfoxide did not. The reaction between hypochlorous acid and nitrite yields nitrating species such as nitrogen dioxide or nitronium ion. Nitrite could protect E. coli by removing toxic nitrating species by hypochlorous acid.

Amines↗

PubMed1994

[The content of nitrates and nitrites in fruits, vegetables and other foodstuffs].

There are presented the results of the investigation of many popular fresh and frozen vegetables as well as in fresh and frozen fruits, such as different kind of apples, strawberries, currants, raspberries and many other tender fruits mainly from market and few from own allotment-cottages performed in the year 1989-1992. The nitrate and nitrite was determined according to the Griess reaction. High levels of nitrate was encountered in lettuce, frozen spinach, fennel, radishes, parsley. Many of this samples contained more than 1000 mg of KNO3/kg of fresh product, but the highest level, over the 3500 mg/kg was found in lettuce. The remaining vegetables like carrots, celery, leeks and frozen French bean contained from several dozen to more than 800 mg KNO3/kg. The level of nitrite in all samples of the investigated vegetables and fruits was very low from zero to decimal part of milligram per kg. Very low level of nitrate was found in 7 species of investigated apples (from 1.3 to 9.7 mg KNO3/kg). A little higher level of this compound was ascertained in currants, gooseberries, raspberries, cherries (from 0.0 to 36.0 mg KNO3/kg product). The highest levels of nitrate occurred in samples of strawberries (maximum to 322.3 mg KNO3/kg) but mean level amounted 58.7 mg KNO3/kg. The encountered levels of nitrate in frozen vegetables and fruits as well as in jams and stewed fruits was only little less than in fresh products. Very high level (from 355.30 to 584.53 mg KNO3/kg) was ascertained in the fruit-vegetable juice named "Rinberen" and "Malberen" to which red beet extract was used for their production. It should be pointed out that when the containers of these juice was opened and stored at the room temperature (+20 degrees C) during 30 days, no changes was observed in the level of nitrate and nitrite. In the juice prepared from blanched carrot, the rate of the reduction of nitrate to nitrite has not been lowered, when this product was storage of this juice at room temperature, the mean level of nitrite increased significantly (from 0.14 to 82.89 mg NaNO2/kg) and the level of nitrate lowered from 261.0 to 46.4 mg KNO3/kg. It should be strongly recommended for consumption the juices from carrot only fresh prepared. There are also presented the results of investigation of nitrate in fermented cheeses.(ABSTRACT TRUNCATED AT 400 WORDS)

Cheese↗

PubMed1994

[Content of nitrates and nitrites in early vegetables and potatoes sold in the marketplace of Białystok in the year 1992].

Nitrate and nitrite were determined in early vegetables and potatoes sold in Białystok in 1992. The levels of nitrates and nitrites were determined in 248 samples. Nitrate and nitrite were evaluated spectrophotometrically by the method of the Griess reaction, after reduction of the nitrates to nitrites, with cadmium dust. High values of nitrate were found in the early vegetables: lettuce, young red beets, radishes, dills, parsley, carrots, cucumbers and potatoes. The results were higher than the suggested limit in Poland. The nitrite contents, except for carrots, were determined in selected vegetables and potatoes.

Environmental Monitoring↗

PubMed1977

Nitrites, nitrosamines, and meat.

Food additive regulations are frequently misunderstood and are often the basis for widely disparate views. The US Department of Agriculture (USDA) does not accept the concept that zero health risk with food additives is a humanly attainable goal; however, if the USDA is to accept that zero health risk is not attainable, then the department must propose, through regulations, a socially acceptable level of risk. Nitrite is an example. On one hand, nitrite is toxic at high levels and can combine with amines to form nitrosamines, which have been shown to cause cancer in animals. On the other hand, nitrite has been shown to provide the necessary protection, in many products, against Clostridium botulinum. The USDA, however, is not content to accept this position as a final one; they will continue to urge additional studies designed to further refine and decrease nitrite usage or replace it with a safe substitute. Given adequate information as to the relative risks involved in the use of nitrite or a substitute, society itself should be in a position to make the determination as to its willingness to accept potential risks in its daily life.

Animals↗