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PubMed1984

Effect of dietary vitamin E on nitrite-treated rats.

The effect of dietary vitamin E on cellular responses to nitrite was studied in rats. One-month-old male Sprague-Dawley rats were fed a basal vitamin E-deficient diet with or without 100 ppm vitamin E and 1000 ppm sodium nitrite (NaNO2) for 9 weeks. In addition to a high mortality rate, nitrite-fed rats maintained on a vitamin E-deficient diet exhibited a marked increase in liver necrosis, tubular nephrosis and myodegeneration, as well as greater biochemical and hematological alterations when compared to the control animals. No animal mortality or histopathologic lesions in any tissues were observed in rats receiving a vitamin E-supplemented diet with or without nitrite. The results suggest that depletion of vitamin E renders rats more susceptible to the adverse effect of nitrite, and that nitrite administration potentiates deficiency of vitamin E in rats.

Animals↗

PubMed2004

Decreased adrenomedullin and total nitrite levels in breast milk of preeclamptic women.

OBJECTIVE: To observe the adrenomedullin (AM) and total nitrite levels in the milk of preeclamptic and normal pregnant women. DESIGN AND METHODS: Fifteen women with preeclampsia and 15 normal pregnant women were included in the study. Total nitrite was quantitated by Griess reaction, while AM was measured by HPLC. RESULTS: The levels of AM and total nitrite in colostrum and 30th-day breast milk were decreased in preeclamptics. Total nitrite levels (micromol/l) were 56.09 +/- 11.18 vs. 82.20 +/- 12.01, P < 0.05, in colostrum of preeclamptics and controls, respectively. The level of total nitrite was 37.75 +/- 12.10 vs. 53.28 +/- 10.25, P < 0.05, in 30th-day milk of same patients. AM levels (pg/ml) were 11.18 +/- 1.11 vs. 16.59 +/- 1.24, P < 0.0001, in colostrum of preeclamptics and controls, respectively. In 30th-day milk of same patients, AM levels were 8.41 +/- 1.39 vs. 12.18 +/- 1.48, P < 0.005, respectively. CONCLUSION: This report shows for the first time that human milk has decreased levels of AM and total nitrite in preeclampsia.

Adrenomedullin↗

PubMed2006

Analysis of nitrite and nitrate in biological samples using high-performance liquid chromatography.

Various analytical techniques have been developed to determine nitrite and nitrate, oxidation metabolites of nitric oxide (NO), in biological samples. HPLC is a widely used method to quantify these two anions in plasma, serum, urine, saliva, cerebrospinal fluid, tissue extracts, and fetal fluids, as well as meats and cell culture medium. The detection principles include UV and VIS absorbance, electrochemistry, chemiluminescence, and fluorescence. UV or VIS absorbance and electrochemistry allow simultaneous detection of nitrite and nitrate but are vulnerable to the severe interference from chloride present in biological samples. Chemiluminescence and fluorescence detection improve the assay sensitivity and are unaffected by chloride but cannot be applied to a simultaneous analysis of nitrite and nitrate. The choice of a detection method largely depends on sample type and facility availability. The recently developed fluorometric HPLC method, which involves pre-column derivatization of nitrite with 2,3-diaminonaphthalene (DAN) and the enzymatic conversion of nitrate into nitrite, offers the advantages of easy sample preparation, simple derivatization, stable fluorescent derivatives, rapid analysis, high sensitivity and specificity, lack of interferences, and easy automation for determining nitrite and nitrate in all biological samples including cell culture medium. To ensure accurate analysis, care should be taken in sample collection, processing, and derivatization as well as preparation of reagent solutions and mobile phases, to prevent environmental contamination. HPLC methods provide a useful research tool for studying NO biochemistry, physiology and pharmacology.

Animals↗

PubMed2005

Urine nitrite not correlated with bacterial resistance to cephalosporins.

Previous research has failed to identify urine nitrite as a useful marker for bacterial resistance to trimethorprim/sulfamethoxazole (TMP/SMX). Evolving resistance to TMP/SMX has encouraged the use of alternate antibiotics, including first-generation cephalosporins. The objective of this study was to reanalyze the relationship between urine nitrite results and bacterial resistance, focusing on first-generation cephalosporins. This was a retrospective review of consecutive culture positive urinalyses collected from December 2002 to July 2003. The majority of the 642 cultures reviewed contained Esherichia coli (74%). Thirty-six percent (233/642) were nitrite positive. Ten percent (24/233) of the nitrite positive urines were resistance to first-generation cephalosporin (cefazolin). In the nitrite-negative group 15.0% (62/409) were resistant. This difference was not statistically significant. We conclude that the detection of urine nitrites should not influence the use of first-generation cephalosporins for urinary tract infection.

Cephalosporins↗

PubMed2006

Crystal structures of the nitrite and nitric oxide complexes of horse heart myoglobin.

Nitrite is an important species in the global nitrogen cycle, and the nitrite reductase enzymes convert nitrite to nitric oxide (NO). Recently, it has been shown that hemoglobin and myoglobin catalyze the reduction of nitrite to NO under hypoxic conditions. We have determined the 1.20 A resolution crystal structure of the nitrite adduct of ferric horse heart myoglobin (hh Mb). The ligand is bound to iron in the nitrito form, and the complex is formulated as MbIII(ONO-). The Fe-ONO bond length is 1.94 A, and the O-N-O angle is 113 degrees . In addition, the nitrite ligand is stabilized by hydrogen bonding with the distal His64 residue. We have also determined the 1.30 A resolution crystal structures of hh MbIINO. When hh MbIINO is prepared from the reaction of metMbIII with nitrite/dithionite, the FeNO angle is 144 degrees with a Fe-NO bond length of 1.87 A. However, when prepared from the reaction of NO with reduced MbII, the FeNO angle is 120 degrees with a Fe-NO bond length of 2.13 A. This difference in FeNO conformations as a function of preparative method is reproducible, and suggests a role of the distal pocket in hh MbIINO in stabilizing local FeNO conformational minima.

Animals↗

PubMed2005

Gastrointestinal bacteria generate nitric oxide from nitrate and nitrite.

Denitrifying bacteria in soil generate nitric oxide (NO) from nitrite as a part of the nitrogen cycle, but little is known about NO production by commensal bacteria. We used a chemiluminescence assay to explore if human faeces and different representative gut bacteria are able to generate NO. Bacteria were incubated anaerobically in gas-tight bags, with or without nitrate or nitrite in the growth medium. In addition, luminal NO levels were measured in vivo in the intestines in germ-free and conventional rats, and in rats mono-associated with lactobacilli. We show that human faeces can generate NO after nitrate or nitrite supplementation. Lactobacilli and bifidobacteria generated much NO from nitrite, but only a few of the tested strains produced NO from nitrate and at much lower levels. In contrast, Escherichia coli, Bacteroides thetaiotaomicron, and Clostridium difficile did not produce significant amounts of NO either with nitrate or nitrite. NO generation in the gut lumen was also observed in vivo in conventional rats but not in germ-free rats or in rats mono-associated with lactobacilli. We conclude that NO can be generated by the anaerobic gut flora in the presence of nitrate or nitrite. Future studies will reveal its biological significance in regulation of gastrointestinal integrity.

Adult↗

PubMed2006

Nitrite regulates distribution of excitation energy between the two photosystems by causing state transition.

The mechanism of distribution of absorbed excitation energy between the two photosystems in the presence of nitrite has been investigated in spinach (Spinacia oleracea L.) thylakoid membranes. Nitrite inhibited PS II activity (H(2)O --> DCPIP reaction) and enhanced PS I activity (DCPIPH(2) --> MV reaction). Nitrite decreased the F(v)/F(m) ratio measured at room temperature and increased the F(730)/F(685) ratio measured at low temperature (77 K). These results suggested that nitrite caused a decrease in the excitation energy available to PS II and transferred more energy to PS I by the mechanism of state transition. Measurement of fluorescence excitation spectra at 77 K showed that nitrite increased the absorption cross-section of PS I antenna at the expense of chlorophyll b and LHC II. Based on these observations we have suggested a role of nitrite in causing state transition.

Chlorophyll↗

PubMed2004

Reaction of phenol with nitrite ion: pathways of formation of nitrophenols in environmental waters.

When sodium nitrite is spiked into phenolic waters, 2-nitrophenol is produced immediately while 4-nitrophenol forms in minor yield after an induction period. The reaction occurs at ambient temperature under acidic, neutral and alkaline conditions. The reaction also occurs in the dark. The nature and yield of the products formed in the dark are analogous to that obtained under ordinary light. Results show that the formation of 2-nitrophenol is first order in nitrite, however, within a narrow range of concentrations. No such order of reaction could be determined for 4-nitrophenol, the yield of which increases in presence of excess nitrite ions and at high nitrite to phenol ratios. Results of this study indicate that NO(2)(-) is the active species in the reaction, attacking the phenol ring at the ortho position and at the same time undergoing a para-substitution in excess nitrite atmosphere. Neither any photo-induced oxidation nor any nitronium ion, NO(2)(+) formation is involved as active species in the nitration of phenol. Our study indicates that in environmental waters a simple contact of nitrite ion with phenolic wastewaters under ambient conditions may form mononitrophenols, which are toxic to aquatic species.

Disinfectants↗

PubMed2004

Effect of nitrite on phosphate uptake by phosphate accumulating organisms.

In biological nitrogen removal processes, nitrite can be formed and accumulated through both nitrification and denitrification. Despite the fact that, in practice, biological phosphate removal (BPR) is often combined with biological nitrogen removal, there are only a few publications reporting the effect of nitrite on BPR. In this study, phosphate-accumulating organisms (PAO) were cultivated in an anaerobic-anoxic-aerobic sequencing batch reactor (SBR). The effect of nitrite on the enrichment of the sludge with PAO, the phosphate uptake rates and the sludge respiration was investigated. The results indicate that (1) presence of nitrite inhibits both aerobic and anoxic (denitrifying) phosphate uptake, (2) aerobic phosphate uptake was more affected than anoxic phosphate uptake, (3) presence of nitrite could be one of the factors enhancing the presence of glycogen accumulating organisms (GAO)--competitors to PAO for substrate in the anaerobic phase, and (4) it is required to monitor and control nitrite accumulation in a full-scale wastewater treatment plants.

Bacteria, Anaerobic↗

PubMed1999

Neuropeptide Y and nitrite levels in preeclamptic and normotensive gravid women.

OBJECTIVES: Vascular tone is controlled largely by the sympathetic nervous system and is modulated by neuropeptide Y. Preeclampsia is linked to sympathetic overactivity. Nitric oxide can cause vasorelaxation of vessels or decrease sympathetic outflow by activating the baroreceptor reflex. Our purpose in this study was to compare serum levels of neuropeptide Y and nitrite levels in normotensive and preeclamptic gravid women. STUDY DESIGN: Twelve preeclamptic and 12 normotensive women matched for race, body mass index, parity, and gestational age were studied. Neuropeptide Y was measured by using a commercial radioimmunoassay. Nitric oxide was converted to nitrite by using metallic cadmium, and nitrite levels were determined spectrophotometrically by using a colorimetric assay. Data are presented as mean +/- SEM and were compared by using a t test. RESULTS: Neuropeptide Y levels were similar among preeclamptic and normotensive gravid women (33.8 +/- 3.0 and 32.2 +/- 3 pg/mL, respectively). Similarly, there were no differences in nitrite concentrations between preeclamptic and normotensive patients (11.6 +/- 0.8 vs 11.2 +/- 0.4 micromol/L, respectively). We also examined the ratios of neuropeptide Y and nitrite and found no correlation between preeclamptic and normotensive women. CONCLUSION: Peripheral levels of neuropeptide Y or nitrite do not correlate with preeclampsia. Assessment of sympathetic overactivity in preeclampsia requires an alternate model.

Adult↗

PubMed2001

The concentration of nitrite in seminal plasma does not correlate with sperm concentration, sperm motility, leukocytospermia, or sperm culture.

OBJECTIVE: To correlate the concentration of nitrite (the stable metabolite of nitric oxide) in seminal plasma with sperm number and motility, leukocytospermia, and sperm culture. DESIGN: Prospective study. SETTING: Academic research institution. PATIENT(S): Seventy normozoospermic or dyspermic men enrolled in an artificial insemination/in vitro fertilization program. INTERVENTION(S): Semen samples (n = 70) were checked for sperm concentration, total sperm count, sperm motility, seminal leukocyte concentration, and sperm culture; similarly, the concentration of nitrite in seminal plasma was measured by Griess reaction. MAIN OUTCOME MEASURE(S): Measurement of nitrite concentration in seminal plasma and its correlation with sperm concentration, total sperm count, sperm motility, leukocytospermia, and sperm culture. RESULT(S): The concentration of nitrite in seminal plasma does not correlate with sperm concentration, total sperm count, or with the proportion of immotile or rapid-forward motile spermatozoa. Moreover, the concentration of nitrite in seminal plasma is not significantly increased when sperm culture is positive, nor does it correlate with leukocyte concentration in semen. CONCLUSION(S): Our results do not support the hypothesis that in vivo nitric oxide synthesis affects sperm function; alternatively, our results could suggest that nitrite in the seminal plasma is not a sensitive marker of in vivo nitric oxide synthesis.

Fertilization in Vitro↗

PubMed2001

Influence of sediment and pore-water composition on nitrite accumulation in a nitrate-perfused freshwater sediment.

Anaerobic nitrate consumption was accompanied by the accumulation of nitrite in the range of 3-52 micromoll(-1) in laboratory sediment cores continuously perfused with nitrate from below. Highest interstitial nitrite concentrations were observed in organically poor sediment cores with a low extractable protein content. Supplemented with an additional source of fixed nitrogen (ammonium), the nitrate-perfused sediments exhibited considerably lower nitrite concentrations than the respective control treatments. The simultaneous addition of ammonium and chloramphenicol, however, resulted in high nitrite concentrations. This suggests that in the absence of chloramphenicol an ammonium-fuelled bacterial protein de novo synthesis prevented the accumulation of nitrite in the course of anaerobic nitrate consumption. Additional DOC (glucose, methanol) generally increased the anaerobic nitrate consumption rate and the interstitial nitrite concentrations. The different scales of these increases were probably related to the degradability of the respective DOC compound and to the taxonomic composition of the microbial community evolving under different feeding regimes.

Anaerobiosis↗

PubMed1998

Augmenting effect of opioids on nitrite production by stimulated murine macrophages.

The effects of methionine-enkephalin and the selective agonists of mu-, delta- and kappa-opioid receptor subtypes [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin, [D-Pen(2,5)]enkephalin U-50488 on the production of nitrite by activated peritoneal murine macrophages were studied. Macrophages were activated with interferon-gamma plus lipopolysaccharide in the presence or absence of graded concentrations of opioids. Methionine-enkephalin and mu-; delta- and kappa-agonists combined with interferon-gamma plus lipopolysaccharide caused an increase in nitrite release from cultured macrophages. Only 10 mM U-50488 led to a decrease in nitrite release from interferon-gamma and LPS-stimulated macrophages. This effect was not produced in a naloxone-sensitive manner. The opioids added to the fresh culture 8 h after the stimulation of macrophages by interferon-gamma plus lipopolysaccharide--when an inducible form of nitric oxide synthase activity is presumably expressed--did not alter the rate of nitrite production. This suggests that the effect of opioids on nitric oxide synthase is produced at the transcriptional level. The opioid receptor antagonist naloxone reduced the stimulatory effect of opioids on nitrite production by stimulated macrophages. Opioids added to the culture of resting macrophages did not change nitrite release from macrophages which were later induced with interferon-gamma plus lipopolysaccharide. The results of this study suggest that methionine-enkephalin can modulate the immune response by controlling, via opioid receptors, the production of nitric oxide.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1996

Mutagenicity of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid treated with nitrite in the presence of alcohols.

The mutagenicity of a product produced from 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCCA), which is a component in soy sauce, after treatment with 50 mM nitrite at pH 3, 37 degrees C, for 60 min in the presence of 7.5% ethanol was much higher than that in the absence of ethanol during the nitrite treatment. The enhancement of the mutagenicity of nitrite-treated MTCCA by ethanol required simultaneous treatment of MTCCA with nitrite and ethanol. The mutagenicity of MTCCA treated with nitrite in the presence and absence of ethanol was detected in the same fractions on HPLC and was highest for Salmonella typhimurium strain YG1029 possessing elevated O-acetyltransferase activity among the several Salmonella test strains, suggesting that the same mutagen belonging to aromatic compounds was produced both in the presence and absence of ethanol. Methanol, n-propanol and isopropanol as well as ethanol were also observed to have an augmenting effect. However, the sugars glucose and sucrose had no effect. When MTCCA was treated with nitrite in the presence of commercial alcoholic beverages equivalent to 1.25-10% ethanol, Japanese 'sake' and 'shochu' were demonstrated to have a highly augmenting effect and beer, wine, whisky and brandy to have a mildly augmenting effect.

Alcoholic Beverages↗

PubMed2003

Reliability of serum iron, ferritin, nitrite, and association with risk of renal cancer in women.

Reliability of serum levels of iron, ferritin and nitrite (NO(2)(-)) over a 2-year period were evaluated in 40 healthy women (20 pre-menopausal and 20 post-menopausal), ages 39-65 years, from the New York University Women's Health Study (NYUWHS). Three blood samples per woman collected at yearly intervals were analyzed. Reliability coefficients (RCs) of serum iron, ferritin, and nitrite were 0.03 (95% confidence interval (CI), 0-0.33), 0.90 (95% CI, 0.79-0.95), and 0.72 (95% CI, 0.50-0.86), respectively, for pre-menopausal women, and 0.26 (95% CI, 0-0.56), 0.77 (95% CI, 0.59-0.89), and 0.55 (95% CI, 0.30-0.77), respectively, for post-menopausal women. In a case-control study nested within NYUWHS cohort, serum levels of nitrite, ferritin, and iron were measured in women apparently healthy at the time of blood donation but diagnosed with renal cancer 1.8-12.2 years later (n=24) and in individually matched controls (two per case). The results suggest that high serum levels of ferritin and nitrite may be associated with a decreased risk of renal cancer (odds ratio (OR), 0.55, 95% CI, 0.15-2.01 for ferritin, and OR, 0.52, 95% CI, 0.17-1.60 for nitrite in women with above median level as compared to women with below median level). The possible role of ferritin and nitrite in renal cancer is discussed.

Adult↗

PubMed2002

Cytotoxicity by nitrite inhalants is not related to peroxynitrite formation.

Nitrite inhalant abuse has been correlated with HIV and Kaposi's sarcoma. Mouse models of inhalant exposure show immunosuppression and loss of immune cells. In the present study, isobutyl nitrite caused a dose-dependent loss of viability of a macrophage cell line. In the absence of cells, isobutyl nitrite reacted with hydrogen peroxide to form peroxynitrite. However, assays of mitochondrial respiration and nitration that detect peroxynitrite indicated that very little was present in cell cultures following exposure to the inhalants. Isobutyl, isoamyl, and butyl nitrites inhibited mitochondrial respiration, but only at high concentrations. Similarly, the nitrating activity of isobutyl nitrite occurred only at high concentrations and was not affected by the presence of hydrogen peroxide. Western blots showed that the inhalant did not increase nitrotyrosine formation in RAW cells or in peritoneal exudate macrophages (PEM) from exposed mice. Thus, the toxicity induced by isobutyl nitrite was probably not due to peroxynitrite formation.

Administration, Inhalation↗

PubMed2002

Nifurtimox biotransformation to reactive metabolites or nitrite in liver subcellular fractions and model systems.

Liver microsomal (mic); nuclei (N) and mitochondria (mit) anaerobically nitroreduce Nifurtimox (Nfx) in the presence of NADPH generating system. Simultaneous formation of small amounts of nitrite was observed in microsomes and nuclei but not in mitochondria. The microsomal nitroreductase activity was enhanced by the presence of flavine-adenine-dinucleotide disodium salt (FAD), was not inhibited by CO and was significantly inhibited by diphenyleneiodonium (DPI). In the microsomal NADPH-dependent fraction nitrite formation was null in the presence of FAD, DPI and under air and was partially inhibited by pure CO. Pure human cytochrome P450 reductase in the presence of NADPH significantly nitroreduced Nfx and produced small amounts of nitrite. The nitroreductive process was significantly enhanced by FAD but the nitrite formation became null. FAD itself was able to chemically nitroreduce Nfx without production of nitrite. NADPH generating system enhanced the FAD nitroreductive effect and led to small production of nitrite. Formation of reactive metabolites and nitric oxide during Nfx metabolism might contribute to its toxicity.

Anaerobiosis↗

PubMed2000

Ion chromatographic method for simultaneous determination of nitrate and nitrite in human saliva.

A simple, rapid, accurate and sensitive method is proposed for the simultaneous determination of nitrite and nitrate in human saliva. Nitrite and nitrate present in the human saliva were determined after 10- to 100-fold dilution with ion chromatography (IC) using suppressed conductivity detection. Recoveries of nitrite and nitrate were found to be ranged between 95% and 101%. The method was linear (r2=0.9991) over the concentration working range. The detection limits were found to be 15.0 microg/l and 33.5 microg/l, for nitrite and nitrate, respectively. Ions that are present in human saliva and several other ions that are suspected to affect nitrite and nitrate determination were checked. It was found that most of the ions did not cause any interference in the determination. The method allows simultaneous determination of nitrite and nitrate in human saliva.

Chromatography, Liquid↗