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PubMed1991

Urinary nitrate, nitrite and N-nitroso compounds in bladder cancer patients with schistosomiasis (bilharzia).

Urinary excretion of nitrite and of volatile and nonvolatile N-nitroso compounds is increased in schistosomiasis (bilharzia) patients with Schistosoma haematobium infection. This observation suggests that the formation of nitrite and N-nitroso compounds in vivo in the urinary bladder of bilharzial patients may be an important etiological factor in the induction of bladder cancer associated with S. haematobium infection.

Adult↗
PubMed1977

Biological interactions of N-nitroso compounds: a review.

There have been efforts to acquire information on the carcinogenic hazards of environmental materials to which humans are exposed since the earliest indications that chemicals can induce cancer in man. N-Nitroso compounds represent a major class of important chemical carcinogens and mutagens that have been implicated as hazardous substances in the environment. This review discusses the relevant chemistry and biotransformation of N-nitroso compounds. It also considers the interaction of these compounds with biological material. Nitrosamines and nitrosamides have been shown to be versatile tools for the study of mutagenic and carcinogenic processes and also lend themselves to structure/activity studies. Attention is drawn to recent developments concerning the relationship between mammalian metabolism of N-nitroso compounds and the relative susceptibility to carcinogenesis and mutagenesis. The usefulness of nitrosamines and nitrosamides in mutagenicity and carcinogenicity studies has been amply demonstrated, and continued work with these substances can lead to a better understanding and evaluation of the potential risks of chemicals in the environment.

Alkylating Agents↗
PubMed1991

Recent studies in Canada on the occurrence and formation of N-nitroso compounds in foods and food contact materials.

We present data on the levels of both volatile and nonvolatile N-nitroso compounds in various smoked meats, including bacon, and in food contact materials (e.g., baby bottle rubber nipples and pacifiers). Evidence presented suggests that the formation of N-nitrosothiazolidine and N-nitrosothiazolidine 4-carboxylic acid in smoked meats and bacon and that of N-nitroso-N-methylaniline in Icelandic smoked mutton, can be minimized by changing or modifying the smoking methods. The presence of two other nonvolatile N-nitroso compounds in these products is also reported.

Canada↗
PubMed1997

[Study of N-nitroso compounds which have NO-release ability].

Nitric oxide (NO), which plays an important role in the vital functions of organisms, is gaseous and labile molecule. Much attention has been paid to the stability and easily handling of NO donors, for careful handling of NO is required during experimental work. We synthesized a series of aromatic N-nitrosoureas and N-nitrosamides which efficiently liberates NO at room temperature. Generation of NO from the aromatic N-nitroso compounds was chemically confirmed by the trapping of NO as a nitrosyl complex of tetraphenylporphyrinatocobalt (II) and spectrophotometrically quantified by means of the Griess reaction using a newly designed test apparatus. 3,3-Dibenzyl-1-(4-tolyl)-1-nitrosourea showed the greatest NO-generating ability among the synthesized N-nitroso compounds. Further, the NO-generating ability was related to the reciprocal of the ID50 value for growth inhibition of cultured L-5178Y cell by the aromatic N-nitroso compounds.

Cell Division↗
PubMed1986

Occurrence of nitroso compounds in fungi-contaminated foods: a review.

Dimethylnitrosamine (NDMA), diethylnitrosamine (NDEA), methylbenzylnitrosamine, and a new N-nitroso compound, N-3-methylbutyl-N-1-methylacetonylnitrosamine (NMAMBA), were found in cornbread that was inoculated with Fusarium moniliforme and underwent an incubation and the addition of a small amount of NaNO2. The carcinogenicity of NMAMBA was shown by the induction of forestomach carcinomas and liver tumors in mice and rats. Another new nitrosamine, N-2-methylpropyl-N-methylacetonyl nitrosamine, was isolated in millet and wheat flour after similar treatment. Some species of fungi not only can reduce nitrates to nitrites but also can increase the amount of secondary amines in the moldy foods and provide favorable conditions for the synthesis of nitrosamines. Some fungi may utilize primary amines to synthesize nitrosamines in appropriate culture mediums. Furthermore, the cornmeal may naturally contain trace amounts of nitrosamines, as detected by a gas chromatography/thermoenergy analyzer. Prolonged feeding of F. moniliforme-inoculated cornbread alone also induced the development of forestomach carcinoma in rats. This indicates the occurrence of potential carcinogens, perhaps certain Fusarium mycotoxins, in the moldy cornbread in addition to the carcinogenic nitrosamines. Another nitroso compound, Roussin red methylester (di-mu-methanethiolatotetranitrosodiiron) was found in pickled vegetables that are eaten daily in the Linxian (China) area. Roussin Red may provide NO-2 ions, which would react readily with secondary amines to form nitrosamines. Possibly this compound is a natural tumor promoter and is able to induce epithelial hyperplasia of the upper digestive tract and forestomach papilloma in treated mice. Also, trace amounts of NDMA, NDEA, and some other nitrosamines were found in the extract of pickled vegetables.

Animals↗
PubMed1987

Laser photofragment spectroscopy: a new technique for the detection of N-nitrosamines and other nitroso compounds.

The potential of laser photofragment spectroscopy (LPS) for the detection and discrimination of nitrosamines, alkyl nitrites, thionitrites and C-nitroso compounds has been evaluated. The technique combines high sensitivity with the dramatic specificity of high-resolution spectroscopy and utilizes pulsed laser photodissociation with synchronized detection of the NO photofragment by laser-induced fluorescence (LIF). Using supersonic molecular beam sampling and wavelength tunable photodissociation, LPS can generate well-resolved finger-print spectra characteristic of the parent nitroso compound.

Lasers↗
PubMed1975

Induction of mouse lung adenomas by amines or ureas plus nitrite and by N-nitroso compounds: effect of ascorbate, gallic acid, thiocyanate, and caffeine.

Lung adenomas were induced in strain A mice by chronic treatment with N-nitroso compounds (given in drinking water) and with amines or ureas in food plus NaNO2 in drinking water. We studied the effects of varying the concentrations of three N-nitroso compounds and NaNO2 concentration in the morpholine plus NaNO2 and methylurea plus NaNO2 systems. Sodium ascorbate (NaASC) at the highest level tested (11.5 or 23 g/kg food) gave 89-98% inhibition of adenoma induction by the NaNO2 plus piperazine, morpholine, and methylurea systems. In 7 groups, NaASC produced increases of 15-59% in adenoma induction by nitrosomorpholine (NM) and mononitrosopiperazine (MNP), possibly because the mice consumed more of the nitrosamine solution. Adenoma induction by morpholine plus NaNO2 was strongly inhibited by gallic acid, moderately inhibited by caffeine, and unaffected by thiocyanate (all added to the food). Gallic acid inhibited or had no effect on the action of NM and MNP. We discussed the proposal that NaASC (or perhaps gallic acid) be administered with readily nitrosatable drugs.

Adenoma↗
PubMed1978

An assessment of human exposure to N-nitroso compounds.

Current knowledge on human exposure to N-nitroso compounds is reviewed. Four exposure routes are considered: ingestion, inhalation, dermal and in vivo. The relative importance of various N-nitrosation mechanisms is discussed.

Administration, Topical↗
PubMedDate not supplied

Mutagenesis by N-nitroso compounds in Salmonella typhimurium TA102 and TA104: evidence for premutagenic adenine or thymine DNA adducts.

Mutagenesis induced by the N-nitroso compounds: N-nitrosomethylurea, N-nitrosoethylurea, N-nitrosodi-n-propylamine and N-nitrosopyrrolidine was measured in Salmonella typhimurium TA100, TA102 and TA104. TA100 detects damage mainly at G-C base pairs while TA102 and TA104 can detect damage at A-T base pairs. In general all strains were similarly sensitive, except that TA104 was much less sensitive to high doses of N-nitroso-N-methylurea. In TA104 a significant percentage of the revertants induced by all agents except NMU resulted from point mutations at A-T base pairs, indicating that adenine or thymine DNA adducts are important premutagenic adducts formed by certain N-nitroso compounds.

Adenine↗
PubMed1983

Risk factors for development of primary cancer in the gastric stump. Intragastric nitrites and nitroso-compounds after surgery for duodenal ulcer.

Results are reported from a study on the presence and concentration of nitrites and nitroso-compounds in the gastric juice of 53 patients operated on for duodenal ulcer and in 15 controls. The investigations were made after various postoperative intervals. In the patients who had undergone Billroth II operation, the concentrations of nitrites and of nitroso-compounds were higher than in those with Billroth I operation and in the controls. It is concluded that patients with Billroth II operation may be particularly susceptible to subsequent primary neoplasm of the gastric stump, as a result of the carcinogenic action of these substances.

Adult↗
PubMed2005

[Study on N-nitroso compound in food and its relevant risk factors for esophageal cancer].

OBJECTIVE: To study multiple risk factors of N-nitroso compounds (NOC) in high- and low-risk areas for esophageal cancer in southern China. METHOD: The samples of 24-hr diets and 12-hr overnight urine were collected from 120 male healthy subjects (35-64 years old) selected by a 3-stage random cluster sample procedure in each of the high-risk area (Nanao County) and low-risk area (Lufeng County) for esophageal cancer. The urinary samples were respectively collected from undosed subjects, subjects ingested 500 mg L-proline (together with 200 mg ascorbic acid ) and subjects ingested 500 mg proline. The levels of total NOC (TNOC), N-nitrosamino acids (NAAs), volatile N-nitroso compounds and reductive ascorbic acid (VC) in the samples were measured. By unconditional logistic stepwise regression model, we analyzed the association between the multiple factors of NOC and esophageal cancer mortality. The factors included the intake and excretion levels of various kinds of NOC, the ability of NAAs endogenous formation and its inhibition by VC, and nutrition status of VC in the body. RESULTS: The results of unconditional logistic stepwise regression showed that risk factors entered the model were diet TNOC content (OR 9.613, 95% CI 1.921-48.115) and urinary NAAs level after ingested VC (OR 1.137, 95 % CI 1.001-1.298). CONCLUSION: The higher level of diet TNOC and the lower inhibition ability of NOC endogenous formation by VC were important risk factors on NOC etiology of esophageal cancer in southern China.

Adult↗
PubMed1986

[Carcinogenic hazard of small doses of nitrite in connection with the endogenous synthesis of nitroso compounds].

Carcinogenic risk of small doses of precursors of nitroso compounds, i.e. sodium nitrite (total dose in 0.2-2.0 g/mouse in drinking water) and morpholine (total dose is 0.23 g/mouse in bread) was studied in 520 CBA and 290 C57Bl mice during 96 weeks. It is shown that under these conditions the carcinogenic effect was more pronounced in CBA mice: there was a significant increase in general incidence of tumours, particularly liver tumours and hemoblastoses in CBA females and malignant liver tumours in CBA males.

Animals↗
PubMed1989

Epidemiological evidence for the role of nitroso compounds in human cancer.

Human exposure to N-nitroso compounds (NOC) is not to single compounds but to highly complex mixtures such as food or tobacco products which may contain various NOC, NOC precursors and modulators of NOC metabolism in addition to other known carcinogens. Aetiological models also stress the importance of other cofactors. The interrelationship of these cofactors with relevant NOC exposures and the possible influence of confounding factors need to be considered in order to evaluate the risk related to NOC. This task is made more difficult because the levels of human NOC exposure are often low, and some of the relevant exposure is likely to be from endogenously formed NOC. Nonetheless, current hypotheses reviewed here propose a role for NOC in the aetiology of tobacco-related cancers and of cancers of the bladder, stomach, oesophagus and brain. Data implicating tobacco-specific nitrosamines in the aetiology of cancers of the oral cavity among snuff dippers is most convincing. Evidence from epidemiological studies in support of other NOC/cancer hypotheses is circumstantial and much work remains to be done to define the role of NOC and develop strategies for prevention of these tumours.

Animals↗
PubMed1984

Mutagenic properties of N-cyclopropyl and N-allyl-N-nitroso compounds. Studies on the nature of alkylating species.

A series of directly acting N-nitroso compounds, N-nitroso-N-allyl urea 6, N-nitroso-N-cyclopropyl urea 7, N-nitroso-acetoxymethyl-allylamine 8, N-nitroso-acetoxymethyl- cyclopropylamine 9, N-nitroso(1- acetoxyethyl )allylamine 10 and N-nitroso(1- acetoxyethyl ) cyclopropylamine 11, which may hydrolize to liberate either cyclopropylating or allylating electrophiles, were synthesized and comparatively investigated for mutagenicity in Salmonella typhimurium TA 1535. Hydrolysis rates in aqueous buffered solution do not differ significantly in the allyl- and cyclopropyl series. Analysis of the hydrolysate of all compounds revealed only the presence of allylalcohol and not cyclopropanol . In contrast to the expected equal potencies, due to chemical rearrangement of the alkylating species from cyclopropylcation to allylcation , the results showed that the cyclopropylating analogs were much more effective mutagens than were the allylating compounds. We conclude that for the cyclopropylating compounds the diazonium ion intermediate - and not the free cation - is the alkylating species, during mutagenesis.

Alkylation↗
PubMed1984

A new type of N-nitrosamino acid, N-nitroso-L-thioproline and N-nitroso-L-methylthioprolines, found in human urine as major N-nitroso compounds.

In addition to N-nitrosoproline (NPRO), N-nitrosamino acids of a new type containing sulfur were found as major N-nitroso compounds in the urine of seven healthy subjects. These compounds were detected using a gas chromatograph connected with a Thermal Energy Analyzer (GC-TEA), and they were identified as N-nitroso-L-thiazolidine-4-carboxylic acid (N-nitroso-L-thioproline, NTPRO) and the cis and trans isomers of N-nitroso-L-methylthiazolidine-4-carboylic acid (N-nitroso-L-methylthioproline, NMTPRO) by using gas chromatography-mass spectrometry (GC-MS). The amounts of NPRO, NTPRO and NMTPRO found in 100 mL samples of human urine were 65-471 ng, 67-2 250 ng and 275-5 825 ng, respectively. L-Thioproline was nitrosated 20-60 times faster than L-proline by nitrite over the whole range of acidic pH. The precursors of these new-N-nitrosamino acids containing sulfur may be formed by the reaction of L-cysteine with formaldehyde and acetaldehyde in the human body. These sulfur-containing N-nitroso compounds, NTPRO and NMTPRO, in addition to NPRO, could be useful as probes for investigation the dynamics of nitrosation in the human body.

Chromatography, Gas↗
PubMed2004

Neutrophil-mediated formation of carcinogenic N-nitroso compounds in an in vitro model for intestinal inflammation.

In order to study neutrophil-mediated formation of carcinogenic N-nitroso compounds as a mechanism of inflammation-related colon carcinogenesis, we designed an in vitro model for intestinal inflammation, consisting of a coincubation system with human colon cells (Caco-2 cells) and activated human neutrophils (PMN), as important immunoreactive cells. We investigated whether nitrosamines and nitrosamides could be formed upon addition of dimethylamine, morpholine and methylurea to the coincubations as nitrosatable precursors, which are known to produce carcinogenic N-nitroso compounds. Incubations of pure nitric oxide with dimethylamine and morpholine showed that NO-mediated formation of nitrosodimethylamine and nitrosomorpholine is possible under the incubation conditions. During the coincubations of activated PMN and Caco-2 cells, 0.34 nmol nitrite/10(6) PMN was produced. Dose-dependent formation of NMOR was observed in this PMN/Caco-2 system; addition of 5mM morpholine resulted in a significantly increased NMOR formation of 4.2 nM. However, no detectable NDMA and methylnitrosourea were formed in this coincubation system. These results suggest that activated human neutrophils are able to synthesize carcinogenic N-nitrosamines, e.g. NMOR, which implies a risk of colon carcinogenesis during chronic inflammation. However, the observed relatively low level of nitrosation suggests that also other risk factors are contributing to the association between chronic inflammation and colon cancer risk.

Caco-2 Cells↗
PubMed1984

Carcinogenic N-nitroso compounds and their environmental significance.

A short review is given on the potent and organ-specific carcinogenic effects of N-nitroso compounds. Like many other chemical carcinogens, nitrosamino compounds require activation in vivo via enzymatic alpha-hydroxylation to form alkylating agents as ultimate carcinogens. Since no epidemiological data in man are available, extrapolation of animal data to man are important as well as dose-response studies in risk evaluations. Important aspects of these problems are presented. Finally the environmental impact of N-nitroso compounds is summarized.

Alkylation↗
PubMed1983

Presence in human urine of a new N-nitroso compound, N-nitrosothiazolidine 4-carboxylic acid.

Urine samples collected in several countries from human subjects showed the presence of a number of N-nitroso compounds not previously identified. By several separative procedures and by comparison with authentic material, the major unknown N-nitroso compound was shown to be N-nitrosothiazolidine 4-carboxylic acid (NTCA). Although its origin in human urine is unknown, thiazolidine 4-carboxylic acid, the easily nitrosatable amine precursor, can be formed by reaction of formaldehyde with cysteine in vivo and in vitro. Thus measuring NTCA excreted in the urine may allow monitoring exposure of human subjects to precursors like formaldehyde and NO-3/NO-2.

Chromatography, Gas↗