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PubMed2000

Electrospray ionization mass spectrometry of low-molecular-mass S-nitroso compounds and their thiols.

Low-molecular-mass S-nitroso compounds (R-S-N=O) are potent vasodilators and inhibitors of platelet aggregation. This work describes the electrospray ionization mass spectrometric (ESI-MS) analysis of physiological and synthetic low-molecular-mass S-nitroso compounds and their thiols including S-nitrosoglutathione, S-nitrosocysteine, glutathione and cysteine. Mass spectra of the unlabeled and S-15N-labeled low-molecular-mass S-nitroso compounds investigated are characterized by abundant cations due to [M+H]+, [M+Na]+, [(M+H)-NO]+, [2 M+H]+, and [(2 M+H)-2NO]+. Mass spectra of low-molecular-mass thiols are characterized by abundant cations due to [M+H]+, [M+Na]+ and [2M+H]+. Using off-line electrospray ionization tandem mass spectrometry we unequivocally identified S-[15N]nitrosoglutathione in human red blood cells formed after their incubation with S-[15N]nitrosocysteine. These results suggest that ESI-MS in combination with an appropriate liquid chromatographic system should be a useful analytical approach for the on-line quantitative determination of low-molecular-mass S-nitroso compounds in biological fluids in the presence of their thiols and nitrite. Considerations were made about on-line ESI-MS and quantitative measurements.

Artifacts↗
PubMed1976

[N-nitroso compounds. Analysis and possible carcinogenicity in man].

Much work has been carried out on N-nitroso compounds but their role in human pathology has still to be elucidated. We cannot extrapolate experimental data to the human situation but we do have indirect evidence that nitroso compounds can be carcinogens in man. Although some nitrosamines are organ-specific, the nitroso group induces the development of many different types of cancer in animals It is probable that the same phenomenon occurs in human pathology, and we cannot therefore expect to have special case reports on their carcinogenicity in man. Therefore, an alternative approach to the study of the role of nitrosamines in human pathology would be to establish a correlation between cancer morbidity in some regions and amounts of N-nitroso compounds in the environment. In view of the complexity of the problem of in vivo nitrosamine formation, it is more realistic nowadays to measure exogenous nitrosamines. Many laboratories are currently engaged on studies on N-nitroso compounds, although systematic information on their presence in the environment is scant. Furthermore, the data acquired by different laboratories has been obtained using a variety of methods for sampling, storage, clean-up and identification and estimation, with the result that it is not known to what extent these results are comparable.Therefore, the standardization and determination of comparability of methods for the identification of N-nitroso compounds is the first step towards their quantitation in the environment. Adequate methods are now available for the determination of volatile nitrosamines, down to the mug/dg level, but methods for non-volatile nitrosamines are still in the development stages. In order to avail all interested laboratories of information on analytical methods for volatile nitrosamines, IARC's analytical chemistry laboratory has organized a three part collaborative study using samples of canned luncheon meat. The results of this study were encouraging, and the European Sub-Committee for the Guidance of Collaborative Studies, at its last meeting, recommended that such studies be continued and extendedto include non-volatile nitrosamines. In parallel with the perfection of analytical techniques, IARC has initiated studies on the measurement of volatile nitrosamines in the environment in conjuction with the epidemiological studies on oesophageal cancer at present being carried out. The data collected up to now is far from being complete but it is important in that it represents the first step towards the evaluation of the risk to health of N-nitroso compounds, which constitute a part of the total carcinogenic load in the human environment.

Animals↗
PubMed1987

Structure-activity relations in carcinogenesis by N-nitroso compounds.

For a large number of N-nitroso compounds a comparison of their carcinogenic effects in rats and Syrian golden hamsters has been made. Nitrosamines, which require metabolic activation, and nitrosoalkylamides, which do not, produce quite different tumor responses. There are also large differences in the types of tumor induced in rats and in hamsters. In all the studies doses of the various compounds, equimolar to the extent that was possible, are administered orally. Continuous doses (in drinking water or food) often produce a response different from that after administration of the same compound in pulsed doses (by gavage), even though the same total dose is delivered. Continuous doses of nitrosamines are usually more effective than pulsed doses, but with the nitrosoalkylureas, the reverse is more generally the case. Rat and hamster liver is a common target of many nitrosamines, but rarely of nitrosamides. The most common site of tumor induction in rats by N-nitroso compounds is the esophagus, but the hamster esophagus never responds. The pancreas duct of the hamster is a common target of nitrosamines containing a beta-oxygenated propyl group, but pancreas duct tumors are never seen in rats. Nitrosomethyl-n-alkylamines (with an even numbered carbon chain) induce bladder tumors in rats and hamsters. Many nitrosoalkylureas induce tumors of the nervous system in rats, as well as a great variety of other tumors. In hamsters, nitrosoalkylureas give rise only to tumors of the forestomach and spleen, but no tumors of the nervous system. The similar carcinogenic actions of certain groups of N-nitroso compounds can be related to their generation, directly or by metabolism, of similar simple moieties having certain organs as their target.

Animals↗
PubMed1991

Occurrence of and exposure to N-nitroso compounds in tobacco.

The concentrations of 21 N-nitroso compounds in smokeless tobaccos are presented. Tobacco-specific nitrosamines accounted for 70-90% of the total identified N-nitroso compounds. Daily exposure of smokeless tobacco users to preformed N-nitroso compounds may exceed 200 micrograms/day in certain populations.

Humans↗
PubMed1999

Risk of colorectal and other gastro-intestinal cancers after exposure to nitrate, nitrite and N-nitroso compounds: a follow-up study.

N-nitroso compounds are potent carcinogens detected in foodstuffs. The importance of dietary nitrosamines in relation to human cancer development is, however, uncertain. We studied the relationship between intake of nitrates, nitrites and N-nitrosodimethylamine (NDMA) and risk of cancers of the gastro-intestinal tract in a cohort of 9,985 adult Finnish men and women. During a follow-up period of up to 24 years, 189 gastro-intestinal cancer cases were diagnosed in the cohort, initially free from cancer. Intake of nitrate, nitrite and NDMA were estimated, based on food-consumption data from a 1-year dietary history interview covering the total diet of the participants. A significant positive association was observed between intake of NDMA and subsequent occurrence of colorectal cancer with a relative risk (RR) between the highest and lowest quartiles of intake of 2.12 [95% confidence interval (CI) 1.04-4.33]. Of various sources of N-nitroso compounds, intake of smoked and salted fish was significantly (RR = 2.58, 95% CI 1.21-5.51) and intake of cured meat was non-significantly (RR = 1.84, 95% CI 0.98-3.47) associated with risk of colorectal cancer. No similar association was observed for intake of other fish or other meat. No significant associations were observed between NDMA intake and cancers of the head and neck combined or of the stomach or between nitrate or nitrite intake and risk of cancers of the gastro-intestinal tract. Our results are in line with the idea that N-nitroso compounds can induce colorectal cancer in humans.

Adolescent↗
PubMedDate not supplied

Screening cosmetic products for N-nitroso compounds by chemiluminescent determination of nitric oxide.

Cosmetic products were screened for total N-nitroso compounds by chemiluminescent measurement of nitric oxide liberated by the reductive cleavage of the N-nitroso group. The cosmetic was first partitioned between methylene chloride and water to separate polar and nonpolar N-nitroso compounds. Each extract was then examined for the presence of N-nitroso compounds by adding the cleavage reagent and sweeping the nitric oxide formed into a chemiluminescent analyzer. Although the method is not intended to be quantitative, recovery studies were conducted to determine measurable levels. Recovery studies of polar N-nitroso compounds were conducted by adding N-nitrosodiethanolamine (NDELA) to a cream, a shampoo, and a lotion at 3 levels, i.e., 80, 320, and 960 ppb, and then determining NDELA by the method. Recoveries ranged from 48 to 83% (mean 68%; SD = 11.9). For recoveries of nonpolar N-nitroso compounds, 100, 200, and 500 ppb of N-nitrosomethyltetradecylamine were added to the 3 cosmetic products. Recoveries ranged from 58 to 70% (mean 63%; SD = 5.3).

Cosmetics↗
PubMed1985

Some nitrosoamino acids in bacon adipose tissue and their contribution to the total N-nitroso compound concentration.

The levels of nitrosoamino acids and apparent total N-nitroso compounds in the adipose tissue of raw bacon have been examined. Nitrosoamino acids were detected in 80% of the samples in levels of up to 0.2 mg/kg. Apparent total N-nitroso compounds were present in all samples in concentrations of between 0.4 and 3.7 mg (N-NO)/kg. Nitrosoamino acids accounted for approximately only 1% of the apparent total N-nitroso compounds. The majority of the apparent total N-nitroso compounds in the adipose tissue were associated with the insoluble connective tissue fraction, with the remainder present as chloroform soluble species.

Adipose Tissue↗
PubMed1984

Analysis and occurrence of total N-nitroso compounds in the Japanese diet.

A quantitative technique for differentiating the total N-nitrosamides from the total N-nitroso compounds has been devised. The principle of this method is based on the chemiluminescence response of a nitroso compound under different denitrosating conditions. We also examined the effect of nitrite scavengers on the stability of N-nitroso compounds and found that both ammonium sulfamate and hydrazine sulfate can be satisfactorily used for the detection of chemiluminescence response with hydrogen bromide-acetic acid reagent. A survey of the occurrence of total N-nitroso compounds, total N-nitrosamides, volatile N-nitrosamines, nitrates and nitrites in the Japanese diet has been conducted. Fairly high levels of total N-nitroso compounds were detected in salt-fermented vegetables, the highest being 2 500 micrograms/kg in hakusai-zuke (salt-fermented Chinese cabbage), followed by 253 micrograms/kg in takuan (salt-fermented radish roots). It is noteworthy that the amounts of total N-nitroso compounds in these products almost coincided with those of total N-nitrosamides, although no appreciable amounts, or only trace quantities, of volatile nitrosamines could be detected in these vegetable products.

Diet↗
PubMed1982

N-nitroso compounds in gastric juice and their relationship to gastroduodenal disease.

Of the N-nitroso compounds derived from precursors in gastric juice, only a very small proportion are in the form of volatile N-nitrosamines. However, about 40% of the remainder can be converted by methylation into a form(s) suitable for gas chromatography. In this way, at least 20 individual peaks were detected with the Thermal Energy Analyzer as detector. N-Nitroso compounds have been determined as a group in the fasting gastric juice of normal individuals and patients with conditions including duodenal ulcer, gastric ulcer, atrophic gastritis, pernicious anaemia, gastric carcinoma, dyspepsia with normal endoscopy or subjected to operative procedures, such as vagotomy or partial gastrectomy. Both the levels of N-nitroso compounds and pH values increased significantly with age in normal subjects and in those with pathological conditions. Sex and cigarette smoking had no significant influence. In particular, a positive correlation was found between pH and the level of N-nitroso compounds, with a p value of less than or equal to 10(-6). Their concentration rose from a geometric mean of 0.11 mumol.1(-1) at pH 1.0-1.5, to a value of 1.3 mumol.1(-1) within the pH range 6.5-9.0. Whilst quantitative bacteriology was not carried out, a highly significant relationship was also observed between the concentration of N-nitroso compounds and the availability of nitrate-reducing bacteria. Thus, conditions conducive to gastric cancer are associated with higher levels of compounds responding to group analysis as N-nitrosamines and/or N-nitrosamides.

Adolescent↗
PubMed1984

N-nitroso compounds and human intracranial tumours.

Experimentalists have shown that various N-nitroso compounds are potent nervous system carcinogens, particularly when animals are exposed transplacentally. Information has been obtained concerning exposure to N-nitroso compounds and their precursors in three case-control studies of intracranial tumour patients in Los Angeles County, California. A study of women (185 pairs) found that level of consumption of nitrite-cured meats was related to meningioma development (p = 0.01). In a similar study of meningiomas in men (105 pairs), the association with cured meats was not clear. The most striking results were obtained in a study of young brain tumour patients (209 matched pairs). Increased risk was associated with maternal contact, during pregnancy, with N-nitrosamine-containing substances, such as burning incense (odds ratio, 3.3; p less than 0.01), sidestream cigarette smoke (odds ratio, 1.5; p = 0.03) and face make-up (odds ratio, 1.6; p = 0.02). Increased risk was also associated with maternal use of diuretics (odds ratio, 2.0; p = 0.03) and antihistamines (odds ratio, 3.4; p less than 0.01) and with the level of maternal consumption of cured meats (p less than 0.01). Diuretics and antihistamines contain nitrosatable amines and amides, and cured meats contain nitrites - chemicals which are precursors of N-nitroso compounds. Additional epidemiological studies of nervous system tumours in young people would appear to offer considerable promise for testing the hypothesis that N-nitroso compounds are etiologically related to human neurogenic neoplasms.

Adolescent↗
PubMed1997

Effect of meat and resistant starch on fecal excretion of apparent N-nitroso compounds and ammonia from the human large bowel.

N-nitroso compounds are produced in the human large intestine, but little is known about the dietary modulation of their synthesis at this site. The effects of meat and resistant starch on the fecal excretion of N-nitroso compounds, measured as apparent total N-nitroso compounds (ATNC), were therefore investigated in a crossover study involving eight healthy men. Three controlled diets that differed in the amount of meat (40 or 600 g) and resistant starch (37 g added to 600 g meat diet) were fed in random order, and fecal ATNC, as well as fecal ammonia and parameters of bowel function, were measured after 19 days of dietary adaptation. Mean ATNC excretion during the high-meat period was 114 micrograms/day, three times that during the low-meat period of 35 micrograms/day (p = 0.02); ammonia excretion was twice that during the low-meat period: 2.9 vs. 1.4 mmol/day (p = 0.03). The fecal ATNC were dissolved in the fecal water, and 45% had a molecular weight < 3,000. The addition of readily fermentable resistant starch to the high-meat diet significantly increased stool output from 118 to 153 g/day and decreased fecal pH from 7.2 to 6.6 but had no significant effect on fecal ATNC (151 micrograms/day), ammonia (3.7 mmol/day), whole gut transit time, urinary nitrate, or plasma urea. ATNC produced in the large bowel in association with a high-meat intake could represent an important source of DNA-damaging alkylating agents in the human large bowel.

Adult↗
PubMed1972

Ascorbate-nitrite reaction: possible means of blocking the formation of carcinogenic N-nitroso compounds.

The formation of carcinogenic N-nitroso compounds by the chemical reaction between nitrous acid and oxytetracycline, morpholine, piperazine, N-methylaniline, methylurea, and (in some experiments) dimethylamine was blocked by ascorbic acid. The extent of blocking depended on the compound nitrosated and on the experimental conditions. Urea and ammonium sulfamate were less effective as blocking agents. The possibility of in vivo formation of carcinogenic N-nitroso compounds from drugs could be lessened by the combination of such drugs with the ascorbic acid.

Aniline Compounds↗
PubMed1983

Carcinogenesis by combinations of N-nitroso compounds in rats.

Five N-nitroso compounds were administered individually or in various combinations to groups of 20 female F344 rats to examine possible additive or synergistic effects on mortality rate and the induction of tumours. Combination of the oesophageal carcinogen dinitroso-2,6-dimethylpiperazine with nitrosodiethylamine, which also induces oesophageal tumours, or with nitrosoethylmethylamine, which induces liver tumours, did not appear to increase tumour incidence. Similarly, combination of nitrosodiethylamine with the bladder carcinogen nitrosomethyldodecylamine did not increase the formation of either bladder or oesophageal tumours compared with the effects of either compound alone, although an additive effect was suggested by a higher incidence of liver tumours after the combined treatment than after treatment with either compound alone. Nitrosomethylurethane, which induces tumours of the forestomach in rats, appeared to enhance the effectiveness of nitrosoethylmethylamine and dinitroso-2,6-dimethylpiperazine in inducing tumours of the oesophagus, and increased the rate of death. Nitrosomethylurethane given, at a somewhat higher dose, in combination with both of these compounds increased the incidence of oesophageal tumours even when the treatment lasted only 4 wk. This evidence suggests that additive or synergistic effects of combinations of N-nitroso compounds at low dose rates can be demonstrated in small groups of rats.

Animals↗
PubMed1997

Effect of aromatic nitroso-compounds on superoxide-generating activity in neutrophils.

Aromatic nitroso-compounds such as nitrosobenzene inhibited the respiratory burst of intact neutrophils induced by various stimulants, including phorbol 12-myristate 13-acetate and a chemotactic peptide. The compounds also inhibited NADPH-dependent oxygen consumption by cell-free preparations of neutrophils. This indicates that nitroso-compounds act directly on the NADPH-oxidase system. The inhibitory effects induced by several nitroso-compounds, 2-nitrosotoluene, nitrosobenzene, 4-nitrosophenol, and 1-nitrosopyrrolidine, were examined and their inhibition constants, the concentrations causing 50% reduction of oxygen consumption, were found to be 0.043, 0.173, 0.672, and 32.1 mM, respectively. These values correlated well with the hydrophobicity of the compounds: a more hydrophobic compound was a more potent inhibitor against NADPH oxidase, suggesting that the oxidase has a hydrophobic site(s) for interaction with the inhibitors.

Animals↗