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PubMed1980

[Formation of nitrosamines in cheese products].

Several strains of micromycetes used as fermentation agents in the cheese industry or having led to accidents during cheese making are able to favor the formation of nitrosamines in 60% of the cases. The concentrations observed are similar to those found by other authors with other microorganisms. The results obtained in a semi-synthetic medium are checked during the ripening of experimental camembert type cheese made from milk containing nitrates and cultured with a strain of Penicillium camemberti, which favors very much the synthesis of nitrosamines. The amount of nitrosodimethylamine formed in this cheese increases from 5 to 20 ppb during ripening. A tentative explanation of the mechanism of formation is outlined.

Cheese↗
PubMed1980

[Presence of volatile nitrosamines in food].

122 foods and 46 beers from the north-east of France and other areas are analysed. The solid frozen samples are finely ground, homogenized and suspended in mineral oil. The volatile nitrosamines are vacuum distilled and extracted with dichloromethane from the acidified distillate. The sample is concentrated and analysed with a gas chromatograph coupled to a TEA detector. The liquid samples are directly extracted with dichloromethane. The non grilled cured meat products are lightly polluted. The nitrosodimethylamine and nitrosopiperidine concentrations usually do not exceed 1 ppb. Only two samples out of about thirty are very polluted by the nitrosopiperidine (28,6 and 26 ppb), and also by the nitrosopyrrolidine (3 and 11 ppb). In the other samples this last nitrosamine is seldom and occurs only in trace amounts. The precooked canned meals and the cheese products are rarely and only lightly polluted. However beers are polluted most of the time. The nitrosodimethylamine is found in all the pale beers, with a concentration ranging from 0.1 to 21.3 ppb (m: 3.1). In dark beers the nitrosodimethylamine concentration ranges from 7.2 to 16.8 ppb (m: 10.1) and the nitrosopyrrolidine concentration has a mean value of 0.2 ppb.

Cheese↗
PubMed1981

Volatile N-nitrosamines in dried foods.

An investigation was carried out to determine the levels of volatile N-nitrosamines in several dried food commodities such as malt, instant skim milk powder, infant formula containing milk powder, instant coffee, soup and soup bases, and baby cereals. The method involves vacuum distillation of the sample from 3N KOH or 1% sulfamic acid, followed by extraction of the aqueous distillate with dichloromethane. The dichloromethane extract is then washed with an acidic buffer (to remove amines), dried over anhydrous sodium sulfate, concentrated in a Kuderna-Danish concentrator, and analyzed by gas-liquid chromatography, using a thermal energy analyzer. Detection limit is 0.1-0.5 ppb. Of the samples analyzed thus far, all malts (22 samples) and instant skim milk powders (11 samples ) were positive for N-nitrosodimethylamine (NDMA); average levels were 7.4 ppb (1.3-67.0 ppb) and 0.4 ppb (0.3-0.7 ppb), respectively. Traces of NDMA and/or N-nitrosopyrrolidine were also detected in 3 of 20 dried soups and 5 of 10 instant coffees analyzed. Traces of NDMA and/or N-nitrosopiperidine (NPIP) were detected in 3 of 8 powdered instant formulas. All for baby cereal samples were negative. The identity of NDMA in 14 samples of malt and that of NDMA and NPIP in a infant formula was confirmed by gas liquid chromatography-mass spectrometry; identity of N-nitrosamines in 3 instant coffees and 1 infant formula was independently verified by high pressure liquid chromatographic analysis.

Chromatography, High Pressure Liquid↗
PubMed1978

Survey of cured meat products for volatile N-nitrosamines: comparison of two analytical methods.

A survey has been completed of 106 cured meat samples for 14 volatile N-nitrosamines. N-Nitrosopyrrolidine has been confirmed in fried bacon at levels ranging from 5 to 75 ppb. Unconfirmed trace levels of N-nitrosodimethylamine have been observed in a variety of cured meat products. The comparison of the multidetection gas-liquid chromatographic (GLC)-mass spectrometric method with the mineral oil distillation-thermal energy analyzer (TEA) method for the determination of volatile N-nitrosamines in foods shows good agreement between the analytical methods, especially at the 10 ppb level, and excellent agreement between the GLC and TEA analyses of an identical sample extracts.

Animals↗
PubMed1981

Carcinogenicity in Syrian golden hamsters of N-nitrosamines formed during nitrosation of spermidine.

Several N-nitrosamines are formed during the nitrosation of the polyamines, spermidine and spermine. Since these polyamines may represent a source for the endogenous or exogenous formation of N-nitrosamines, their major nitrosation products were assayed for carcinogenicity in male Syrian golden hamsters. Administration of N-nitroso-3-butenyl(2-propenyl)amine SC once a week for life at a dose of 300 mg/kg induced neoplasms mostly in the upper respiratory tract (nasal cavity, larynx, trachea). Lung microlithiasis (alveolar and bronchial) also developed in all these animals. In contrast, N-nitroso-3-butenyl(3-hydroxypropyl)amine and N-nitroso-4-hydroxybutyl(2-propenyl)amine induced neoplasms, primarily in the digestive tract, including the nonglandular stomach, cecum, colon, and adrenal gland.

Animals↗
PubMed1980

Comparative carcinogenicity in F344 rats of the tobacco-specific nitrosamines, N'-nitrosonornicotine and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco-specific carcinogens, N'-nitrosonornicotine (NNN) and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), were tested for carcinogenicity in F344 rats. Each nitrosamine in trioctanoin was administered by s.c. injection to 12 male and 12 female rats over a period of 20 weeks. The total dose of each nitrosamine was 3.4 mmol. The experiment was terminated after 12 months. NNK induced nasal cavity tumors in 83% of the males and in 83% of the females, liver tumors in 83% of the males and in 100% of the females, and lung tumors in 67% of the males and in 67% of the females. NNN induced nasal cavity tumors in 92% of the males and in 75% of the females. Only one liver tumor and no lung tumors were observed in the NNN-treated rats. These results indicate that, in the F344 rat, NNK is a more powerful carcinogen than is NNN.

Animals↗
PubMed1980

A new assay for the microsomal metabolism of nitrosamines.

This report describes a new general assay for the microsomal oxidative dealkylation of nitrosamines. After precipitation of the microsomal proteins, aldehydes formed from nitrosamines are quantitated by high-pressure liquid chromatography as their 2,4-dinitrophenylhydrazones. This novel assay method offers some distinct advantages over the commonly used Nash reagent assay. Dimethylnitrosamine, diethylnitrosamine, and methylethylnitrosamine were metabolized by microsomes from noninduced male Fischer rat liver, and the aldehydes produced by these reactions were examined. Two distinct kinetic lines were observed for reactions containing dimethylnitrosamine or diethylnitrosamine. Similarly, two Km's were observed for the production of both formaldehyde and acetaldehyde produced by the metabolism of methylethylnitrosamine.

Acetaldehyde↗
PubMedDate not supplied

Supercritical fluid extraction of N-nitrosamines in hams processed in elastic rubber nettings.

A method for analysing N-nitrosamines in hams processed in elastic rubber nettings by supercritical fluid extraction (SFE) is described. The study was carried out with the prototype of a commercial extractor with a silica gel adsorption cartridge integrally attached to the variable restrictor. The SFE method was compared with a solid-phase extraction procedure currently used for ham analysis. Both methods used the same gas chromatographic-chemiluminescence detection conditions. No significant difference (p < 0.05) was found between results obtained with the 2 methods. Repeatability standard deviation of the SFE method was 1.7 ppb, with a coefficient of variation (CV) of 2.7%, compared with 2.2 ppb, with a CV of 3.5%, for solid-phase extraction. SFE permits minimal use of solvent and more rapid analysis of nitrosamines.

Animals↗
PubMed1994

[Effects of selenium on endogenous synthesis of N-nitrosamines and toxicity of nitrites in rats].

Male Wistar rats were fed selenium (0.2, 2.9 or 5.5 mg/kg of dry feed) in the form of selenomethionine. They also received for 6 weeks amidopyrine (33 mg/kg b.w.) and/or sodium nitrite (20 mg/kg b.w.) administered intragastrically. The quantitation of endogenously synthetized volatile nitrosamines in the stomach, selenium in the serum, biochemically evaluated nitrite and nitrosamines toxicity revealed an inverse relationship between feed selenium concentrations and the amount of endogenously produced nitrosodimethylamine from equal precursor doses. A protective selenium effect on methemoglobin-producing action of nitrite ions was established. It is shown that introduction of precursors induces increased body need in selenium.

Aminopyrine↗
PubMed1994

N-nitrosamines in Indian beers.

Presence of volatile N-nitrosamines in beer and other alcoholic drinks are well documented in developed countries. Analysis of 120 beer samples of various brands/batches showed positivity for N-nitrosodimethylamine (NDMA) in more than 100 samples. The overall mean of 3.6 ppb of NDMA is higher than those currently found in Western countries. Since N-nitrosamines are proven carcinogens in animals at several sites it is necessary to keep their levels of exposure to as low as possible.

Beer↗
PubMedDate not supplied

Uptake and metabolism of carcinogenic levels of tobacco-specific nitrosamines by Sudanese snuff dippers.

It was recently reported that toombak, a type of snuff used in the Sudan, contained unusually high levels of tobacco-specific nitrosamines. To estimate the internal dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) received by individuals who use this type of tobacco, urine from a group of users was analyzed for 2 metabolites of NNK, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its O-glucuronide, NNAL-Gluc. NNK is a strong lung carcinogen believed to contribute to human lung cancer. NNAL is also a lung carcinogen. NNAL and NNAL-Gluc were analyzed by gas chromatography with a nitrosamine selective detector. The average levels detected were 0.39 +/- 0.14 (SD) nmol/ml urine (n = 7) and 0.88 +/- 0.50 nmol/ml urine (n = 7), respectively. In a 24-h period, these individuals would excrete from 0.12 to 0.44 mg of these two metabolites (expressed per mg NNAL). Therefore, assuming chronic toombak use, the minimum daily dose of NNK to which these users were exposed was 0.12-0.44 mg. This is the highest documented uptake of a nonoccupational carcinogen. Two diastereomers of NNAL-Gluc were present in all urine samples analyzed. Previously, these two diastereomers were identified in the urine of an NNK-treated patas monkey but only one was detected in the urine of NNK-treated rats. The level of the 4-hydroxy-1-(3-pyridyl)-1-butanone releasing hemoglobin adduct was also quantified in these individuals. This adduct is believed to be a measure of NNK activation. The levels ranged from 68 to 323 fmol/g hemoglobin [mean, 148 +/- 104 (SD)]. The wide range of adduct levels which were observed suggests that despite similar levels of NNK exposure, there are significant differences in the ability of individuals in this population to activate NNK, as well as potential differences in their cancer risk.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1976

[Analysis of volatile N-nitrosamines. A brief review].

The different steps of analysis of volatile N-Nitrosamines: separation from product, clean up, detection, quantification and confirmation are reviewed and discussed. The two best analysis procedures are: 1) combined gas-chromatography; mass-spectrometry, 2) combined gas-chromatography; thermal energy analyzer. However a bundle of proofs is always necessary to ascertain the presence of Nitrosamines.

Chemical Phenomena↗
PubMed1994

Evidence supporting the role of DNA pyridyloxobutylation in rat nasal carcinogenesis by tobacco-specific nitrosamines.

The tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) both induce nasal tumors in rats and have a common metabolic activation pathway leading to pyridyloxobutylation of DNA. The role of DNA pyridyloxobutylation in rat nasal carcinogenesis has not been evaluated previously. In this study, we used gas chromatography-mass spectrometry to compare levels of 4-hydroxyl-1-(3-pyridyl)-1-butanone-releasing adducts formed by pyridyloxobutylation of rat nasal mucosa DNA after treatment with either NNK, NNN, or deuterated analogues of NNK. The latter were [4,4-D2]NNK, a stronger nasal cavity carcinogen than NNK, and [CD3]NNK, which has carcinogenic activity equivalent to NNK. We also investigated toxicity to the nasal mucosa and levels of O6-methylguanine in the DNA of this tissue in rats treated with NNK and its deuterated analogues. Rats were given three times weekly s.c. injections of the respective nitrosamines for 4 weeks and then sacrificed 24 h after the final injection. The nasal mucosa was separated into the olfactory and respiratory portions. In the rats treated with [4,4-D2]NNK, levels of O6-methylguanine in DNA from both the olfactory and respiratory portions of the nasal mucosa were significantly lower and levels of 4-hydroxy-1-(3-pyridyl)-1-butanone-releasing DNA adducts higher than in the rats treated with equivalent doses of the less carcinogenic compounds NNK or [CD3]NNK. 4-Hydroxy-1-(3-pyridyl)-1-butanone-releasing adducts were also detected in the nasal mucosa DNA of the rats treated with NNN. In the comparative study of NNK and its deuterated analogues, the histology of the nasal mucosa did not appear to be markedly different among these groups. Collectively, the results of this study provide strong evidence that DNA pyridyloxobutylation is important in rat nasal cavity carcinogenesis by NNK and NNN.

Alkylation↗
PubMed1993

Metabolites of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in smokers' urine.

Metabolites of the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, a potent pulmonary carcinogen, have been quantified in the urine of 11 smokers. They were not detected in nonsmokers' urine. The metabolites, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronide, were detected in quantities of 0.23-1.0 and 0.57-6.5 micrograms/24 h, respectively. The results of this study provide the first evidence for metabolites of tobacco-specific nitrosamines in human urine.

Adult↗
PubMed1996

Metabolites of a tobacco-specific nitrosamine, 4-(methylnitrosamino)- 1-(3-pyridyl)-1-butanone (NNK), in the urine of smokeless tobacco users: relationship between urinary biomarkers and oral leukoplakia.

Two metabolites of the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone were quantified in the urine of smokeless tobacco users. The metabolites are 4-(methylnitrosamino) -1-(3-pyridyl)-1-butanol (NNAL) and [4-(methylnitrosamino)-1-(3-pyridyl) but-1-yl]-beta-O-D-glucosiduronic acid (NNAL-Gluc). The study population consisted of 47 male nonsmokers, of whom 23 were snuff dippers, 13 were tobacco chewers, 3 were users of both products, and 8 were nonusers. The levels of NNAL-Gluc in urine ranged from 0.14-30.3 pmol/mg creatinine with a mean +/- SD of 3.47 +/- 5.86, whereas the levels of NNAL ranged from 0.02-8.73 pmol/mg creatinine with a mean +/- SD of 0.92 +/- 1.59. The mean levels of NNAL-Gluc and NNAL were not significantly different from those measured in a previous study of smokers. The levels of NNAL-Gluc were significantly higher in snuff dippers than in tobacco chewers. The ratio of NNAL-Gluc:NNAL was higher in snuff dippers than in tobacco chewers or smokers. There was no indication of two phenotypes of the NNAL-Gluc:NNAL ratio in smokeless tobacco users, in contrast to previous observations in smokers. Of the 39 smokeless tobacco users in this study, 16 presented with oral leukoplakia. When the total levels of NNAL-Gluc, NNAL, or NNAL-Gluc + NNAL were divided into tertiles, there was a significant association between the presence of leukoplakia and increasing levels of these metabolites; a similar relationship was found between urinary cotinine and leukoplakia. The results of this study demonstrate that there is significant uptake of carcinogenic nitrosamines in smokeless tobacco users, and that such products are not harmless alternatives to cigarettes. Moreover, the urinary biomarkers NNAL-Gluc, NNAL, and cotinine were associated with the presence of leukoplakia, which provides biochemical support for the role of smokeless tobacco products as a cause of oral leukoplakia.

Adult↗
PubMed1996

Effect of a tobacco-related nitrosamine on intercellular communication in human urothelial cells: a possible factor in smoking-related bladder carcinogenesis.

Bladder cancer is associated with smoking. Among the tobacco-derived carcinogens suspected of being involved in initiating the disease are nitrosamines found in urine. In this study a nitrosamine found in the urine of smokers was tested using a tissue culture model of normal human urothelium. Explant cultures were established from ureters and exposed to 5 ng/ml of the derivative. This level had been demonstrated previously to induce a variety of changes associated with initiation of carcinogenesis. Proliferation of the cultures was increased following exposure to the carcinogen, and the gap junction intercellular communication was reversibly inhibited. Examination of the connexin 43 protein and message status showed that the mRNA was unaffected, but the protein was not detectable using anti-connexin 43 antibody. The expression of the protein recovered within 24 h of removal of the carcinogen, indicating that the continued presence of the agent was necessary. Given the roles of cell proliferation and cell communication in carcinogenesis, the results may suggest a mechanism involving pre- or post-initiation deregulation of cell communication systems. Whether the enhanced growth is a separate effect or a consequence of reduced communication is an intriguing question.

Carcinogens↗
PubMed1997

Effect of vitamin E and beta-carotene on DNA strand breakage induced by tobacco-specific nitrosamines and stimulated human phagocytes.

The tobacco-specific nitrosamines (TSNAs), nitrosonornicotine (NNN) and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are metabolites of nicotine and are major carcinogens in cigarette smoke. Chronic inflammation may promote the carcinogenic effect of these nitrosamines through the generation of oxygen radicals. To evaluate the effect of oxygen radicals on TSNA-induced genetic damage, cultured human lung cells treated with NNN or NNK were exposed to stimulated human phagocytes and assayed for single-strand DNA breaks. TSNAs or stimulated phagocytes alone cause a significant increase in strand breakage which is augmented in an additive fashion when the two are combined. Pretreating the cells with vitamin E or beta carotene provided significant protection against the induction of DNA damage but vitamin E was significantly more effective than beta carotene. These data suggest a possible approach to the chemoprevention of tobacco-induced carcinogenesis.

Carcinogens↗
PubMed1997

[Levels of N-nitrosamine in gastric juice of patients after surgery for ulcers].

The concentration of N-nitrosamines was determined in the gastric juice of 170 patients between 6 months and 33 years after operation for ulcer disease, including 38 patients after resection with the Rydygier method (BI-R), 36 after Billroth II method (BII), 35 after truncal vagotomy with pyloroplasty (VP), 41 after highly selective vagotomy (WWW) and 20 after gastroenterostomy (ZZJ). The concentration of N-nitrosamines in the gastric juice was estimated chromatographically. It was confirmed that their concentration in the stomach was the highest after ZZJ and BII resection, lowest after WWW.

Adult↗