sodium-nitrite and morpholine

The genotoxicity of endogenously formed N-nitrosamines from secondary amines and sodium nitrite (NaNO(2)) was evaluated in multiple organs of mice, using comet assay. Groups of four male mice were orally given dimethylamine, proline, and morpholine simultaneously with NaNO(2). The stomach, colon, liver, kidney, urinary bladder, lung, brain, and bone marrow were sampled 3 and 24 h after these compounds had been ingested. Although secondary amines and the NaNO(2) tested did not yield DNA damage in any of the organs tested, DNA damage was observed mainly in the liver following simultaneous oral ingestion of these compounds. The administration within a 60 min interval also yielded hepatic DNA damage. It is considered that DNA damage induced in mouse organs with the coexistence of amines and nitrite in the acidic stomach is due to endogenously formed nitrosamines. Ascorbic acid reduced the liver DNA damage induced by morpholine and NaNO(2). Reductions in hepatic genotoxicity of endogenously formed N-nitrosomorpholine by tea polyphenols, such as catechins and theaflavins, and fresh apple, grape, and orange juices were more effective than was by ascorbic acid. In contrast with the antimutagenicity of ascorbic acid in the liver, ascorbic acid yielded stomach DNA damage in the presence of NaNO(2) (in the presence and absence of morpholine). Even if ascorbic acid acts as an antimutagen in the liver, nitric oxide (NO) formed from the reduction of NaNO(2) by ascorbic acid damaged stomach DNA.

Topics: Animals; Ascorbic Acid; Beverages; Comet Assay; DNA Damage; Fruit; Liver; Male; Mice; Morpholines; Muscarinic Antagonists; Mutagenicity Tests; Mutagens; Nitrosamines; Proline; Sodium Nitrite; Tea

Reactive nitrogen species, including nitrogen oxides (N(2)O(3) and N(2)O(4)), peroxynitrite (ONOO(-)), and nitryl chloride (NO(2)Cl), have been implicated as causes of inflammation and cancer. We studied reactions of secondary amines with peroxynitrite and found that both N-nitrosamines and N-nitramines were formed. Morpholine was more easily nitrosated by peroxynitrite at alkaline pH than at neutral pH, whereas its nitration by peroxynitrite was optimal at pH 8.5. The yield of nitrosomorpholine in this reaction was 3 times higher than that of nitromorpholine at alkaline pH, whereas 2 times more nitromorpholine than nitrosomorpholine was formed at pH <7.5. For the morpholine-peroxynitrite reaction, nitration was enhanced by low concentrations of bicarbonate, but was inhibited by excess bicarbonate. Nitrosation was inhibited by excess bicarbonate. On this basis, we propose a free radical mechanism, involving one-electron oxidation by peroxynitrite of secondary amines to form amino radicals (R(2)N(*)), which react with nitric oxide ((*)NO) or nitrogen dioxide ((*)NO(2)) to yield nitroso and nitro secondary amines, respectively. Reaction of morpholine with NO(*) and superoxide anion (O(2)(*)(-)), which were concomitantly produced from spermine NONOate and by the xanthine oxidase systems, respectively, also yielded nitromorpholine, but its yield was <1% of that of nitrosomorpholine. NO(*) alone increased the extent of nitrosomorpholine formation in a dose-dependent manner, and concomitant production of O(2)(*)(-) inhibited its formation. Reactions of morpholine with nitrite plus HOCl or nitrite plus H(2)O(2), with or without addition of myeloperoxidase or horseradish peroxidase, also yielded nitration and nitrosation products, in yields that depended on the reactants. Tyrosine was nitrated easily by synthetic peroxynitrite, by NaNO(2) plus H(2)O(2) with myeloperoxidase, and by NaNO(2) plus H(2)O(2) under acidic conditions. Nitrated secondary amines, e.g., N-nitroproline, could be identified as specific markers for endogenous nitration mediated by reactive nitrogen species.

Topics: Aniline Compounds; Hydrogen Peroxide; Hypochlorous Acid; Morpholines; Nitrates; Nitrobenzenes; Nitrosamines; Sodium Nitrite; Superoxides; Tyrosine

The aim of the present study was to examine the chemopreventive efficacy of S-methylcysteine (SMC) on rat hepatocarcinogenesis induced by concurrent administration of sodium nitrite (NaNO(2)) and morpholine (Mor) using a medium-term rat liver carcinogenesis bioassay (Ito test). Administration of SMC caused significant reduction in the areas of glutathione S-transferase placental form positive foci along with a significant decrease of hepatocyte 5-bromo-2'-deoxyuridine (BrdU) labeling indices. These results demonstrated potent chemopreventive effects of SMC against hepatocarcinogenesis due to concurrent administration of Mor and NaNO(2). SMC could thus be an effective chemopreventive agent for decreasing the risk of carcinogenicity from environmental precursors of N-nitroso compounds.

Topics: Animals; Anticarcinogenic Agents; Body Weight; Bromodeoxyuridine; Carcinogens; Cell Division; Cysteine; Drug Interactions; Food Preservatives; Gastric Mucosa; Glutathione Transferase; Liver; Liver Neoplasms, Experimental; Male; Morpholines; Nitrosamines; Precancerous Conditions; Rats; Rats, Inbred F344; Sodium Nitrite

For carcinogenic risk assessment of combinations of N-nitroso precursors in man, the effects of feeding methylurea (MU) or morpholine (Mor) plus sodium nitrite (NaNO2) were investigated using a multi-organ carcinogenesis model. In experiment 1, to initiate multiple organs, groups of 10 or 20 male F344 rats were treated with 6 carcinogens targeting different organs. Starting a week after completion of this initiation phase, animals were given 0.1% MU or 0.5% Mor in their food and/or 0.15% NaNO2 in their drinking water for 23 weeks. The induction of tumors and/or preneoplastic lesions in the forestomach and esophagus was significantly increased in the group receiving MU plus NaNO2. The numbers and areas of liver glutathione S-transferase placental form (GST-P)-positive foci were significantly elevated with MU or Mor plus NaNO2. Experiment 2 was conducted to assess formation of N-nitroso compounds in the stomach, and to detect DNA adduct generation in target organs by immunohistochemical staining. Groups of 5 or 14 animals were starved overnight, then given 0.4% MU or 2.0% Mor in the diet, or basal diet alone for 1 h. Then NaNO2 or distilled water was given intragastrically. The mean gastric N-methyl-N-nitrosourea yield in the MU plus NaNO2 group was 7700 micrograms at 2 h after combined administration. The mean N-nitrosomorpholine yield in the group given Mor plus NaNO2 was 6720 micrograms. Immunohistochemically, N7-methyldeoxyguanosine-positive nuclei were evident in the forestomach epithelium at 8 h after the combination treatment with MU plus NaNO2.

Topics: Administration, Oral; Animal Feed; Animals; Biomarkers, Tumor; Carcinogenicity Tests; Carcinogens; Drug Interactions; Esophageal Neoplasms; Glutathione Transferase; Humans; Liver; Liver Neoplasms; Male; Methylurea Compounds; Morpholines; Neoplasms, Experimental; Nitroso Compounds; Precancerous Conditions; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms; Water Supply

Chronic experiments on CBA and C57B1 mice and acute experiments on CBA mice established: (a) carcinogenic effect of sodium nitrite given continuously with drinking water (0.1; 1.0 and 10.0 maximum allowable concentration) in combination with morpholine fed with bread, and (b) endogenous synthesis of nitrosomorpholine as a result of simultaneous intragastric administration of same doses of sodium nitrite and morpholine. Also, nitrosomorpholine and N-nitrosodimethylamine synthesis was observed in vitro following addition of low-dose sodium nitrite, morpholine and amidopyrine to human gastric juice. Carcinogenic hazard associated with low-dose nitrite consumption in humans is discussed.

Topics: Aminopyrine; Animals; Carcinogens; Dimethylnitrosamine; Female; Food; Gastric Juice; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Morpholines; Nitrites; Nitrosamines; Sodium Nitrite; Water Supply

Experiments used 409 male CBA mice to study the effect of ascorbic acid on carcinogenesis induced by treatment with such precursors of nitroso compounds as sodium nitrite and morpholine. The former was given with feed in a total dose of 573-891 mg/animal and the latter--with drinking water in a total dose of 138-183 mg/animal. As a result, the total number of tumor-bearers grew from 63.8% (controls) to 82.5%. Treatment with all doses of ascorbic acid tested (1.5; 0.25 and 0.025% with drinking water) was followed by reduction in frequency of tumors in animals treated with nitroso compound precursors to 37.9, 55.1 and 60%, respectively.

Topics: Animals; Ascorbic Acid; Male; Mice; Mice, Inbred CBA; Morpholines; Neoplasms, Experimental; Nitrites; Sodium Nitrite

The article deals with a comparison of the results of human body nitrosating ability determination by two methods: (a) nitroso compound (NC) assay in diurnal urine after oral administration of its precursors, and (b) assay of the same in gastric juice after in vitro addition of precursors. The data for the first part of the investigation were obtained from the literature, and for the second one--from the experiments by the authors. Both studies used essentially identical groups of patients, primarily those suffering gastrointestinal pathology. Since the results matched to a considerable degree, it was inferred that (1) gastric juice is a factor of body nitrosating ability, and (2) in vitro determinations of said ability in gastric juice are fully justified. Moreover, the latter procedure is sometimes more practicable, particularly, in view of the marked relationship between nitrosating ability, and, especially, the efficacy of inhibitors of NC endogenous synthesis, on the one hand, and the individual characteristics of the body, on the other.

Topics: Aminopyrine; Dimethylamines; Fasting; Gastric Acidity Determination; Gastric Juice; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Methods; Morpholines; Nitrates; Nitrosamines; Nitroso Compounds; Proline; Sodium Nitrite

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.

Topics: Animals; Disease Susceptibility; Dose-Response Relationship, Drug; Female; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Morpholines; Neoplasms, Experimental; Nitrites; Nitroso Compounds; Sodium Nitrite

Topics: Animals; Ascorbic Acid; Citrus; Food Additives; Male; Morpholines; Mutagenicity Tests; Mutation; Rats; Rats, Inbred Strains; Salmonella typhimurium; Sodium Nitrite

A sensitive method was developed for quantitation of N-nitrosomorpholine (NMOR) formation in vivo in rats. A major metabolite of NMOR, N-nitroso(2-hydroxyethyl)glycine, was detected by gas chromatography-thermal energy analysis in the urine of rats treated with trace levels of NMOR or treated sequentially with morpholine and sodium nitrite. Since significant levels of 2-hydroxyethylglycine do not seem to occur in rat urine, even after treatment with morpholine, artefact formation was not a problem. Formation of 1 micrograms NMOR in vivo was readily detected. The formation of NMOR from morpholine and sodium nitrite in vivo in rats appeared to depend on the doses of morpholine and [sodium nitrite]2 and occurred in higher yield than reported for formation of N-nitrosoproline, as expected. The formation of NMOR from morpholine and sodium nitrite under the conditions of the carcinogenicity study of Shank and Newberne was quantified. The daily levels of NMOR formation were highly variable, but the mean level was consistent with the tumorigenicity data in that dose-response study.

Topics: Animals; Chromatography, Gas; Morpholines; Nitrosamines; Rats; Rats, Inbred F344; Sodium Nitrite

A method was developed to monitor the in vivo formation of N-nitrosomorpholine. N-Nitroso(2-hydroxyethyl)glycine, a major urinary metabolite of N-nitrosomorpholine, was quantified as its methyl ester-trimethylsilyl ether derivative, using gas chromatography with nitrosamine-specific detection. When the method was applied to rats, the in vivo formation of, or exposure to, as little as 0.6 micrograms of N-nitrosomorpholine could be quantified. The method was also applicable to human urine, with a detection limit of approximately 0.5 micrograms of N-nitroso(2-hydroxyethyl)glycine per 100-ml urine sample. The formation of N-nitrosomorpholine was measured in rats treated by gavage with a wide range of doses of morpholine and NaNO2. Depending on the dose, 0.5 to 12% of the morpholine was nitrosated. N-Nitrosomorpholine formation showed a high degree of variability among rats treated with a given dose of morpholine and NaNO2, but the levels of N-nitrosomorpholine formed were generally in agreement with expectations based on in vitro studies in which dependence on morpholine concentration multiplied by nitrite concentration squared has been established. The formation of N-nitrosomorpholine was also measured in rats administered a diet containing 50 ppm of morpholine and 1000 ppm of NaNO2, a regimen which has been previously shown to induce liver cell tumors in 58% of the animals. The mean daily formation of N-nitrosomorpholine under these conditions was estimated to be 0.88 +/- 0.59 mumol/rat (S.D.), which is high enough to account for the observed tumor incidence. The results of this study provide quantitative support for the assumption that in vivo formation of N-nitrosomorpholine leads to tumor development.

Topics: Animals; Carbon Radioisotopes; Carcinogens; Diet; Kinetics; Male; Morpholines; Nitrites; Nitrosamines; Rats; Rats, Inbred F344; Rats, Inbred Strains; Sodium Nitrite