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S S Hecht

Publications and source records attributed to S S Hecht.

At least 181 records · Page 10Linked to original sources
PubMed1989

Chromatographic conditions for separation of 32P-labeled phosphates of major polynuclear aromatic hydrocarbon--deoxyribonucleoside adducts.

The 3'-monophosphates of the major deoxyribonucleoside adducts of five representative polynuclear aromatic hydrocarbons (PAH)-benzo[a]pyrene, benz[a]anthracene, chrysene, 5-methylchrysene and 6-methylchrysene--were prepared by reaction with DNA of the appropriate bay-region diol epoxides followed by enzymatic hydrolysis and HPLC purification. These standards were converted to 3',[32P]-5'-bisphosphates as in the Randerath 32P-postlabeling assay. TLC and HPLC systems for their separation are described. HPLC conditions for separation of the corresponding 3'- and 5'-monophosphates are also reported. These data will be useful for determining whether unknown DNA adducts detected by the 32P-postlabeling assay may have resulted from reactions of DNA with PAH diol epoxides.

DNA↗
PubMed1989

Cell specificity for the pulmonary metabolism of tobacco-specific nitrosamines in the Fischer rat.

The activity and distribution of the metabolic pathways of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and the structurally related nitrosamine, N'-nitrosonornicotine (NNN) were examined in pulmonary cells from F344 rats in order to investigate the mechanisms by which NNK and NNAL, but not NNN, cause lung tumors. The tritium labeled nitrosamines were incubated with Clara cells, alveolar macrophages, alveolar type II cells, or small cells and metabolites were analyzed by HPLC. O6-Methyl-guanine (O6MG) formation was also quantified in the cells incubated with NNK. Clara cells metabolized all compounds more extensively than the other cell types. Total alpha-hydroxylation, carbonyl reduction to NNAL, and pyridine N-oxidation in cells incubated with NNK, as well as concentrations of O6MG in DNA were higher in Clara cells than in other cell types. Carbonyl reduction of NNK predominated over the other metabolic pathways in all cell types. The high activity for alpha-hydroxylation of NNK in Clara cells is consistent with previous studies which proposed that the cell specificity for O6MG formation and the accumulation of this adduct during low-dose exposure to NNK may stem from the presence of a high affinity pathway in Clara cells for NNK activation. Metabolism of NNAL by alpha-hydroxylation, and by reconversion to NNK followed by alpha-hydroxylation were observed. Total alpha-hydroxylation of NNAL was less extensive than alpha-hydroxylation of NNK. NNN was metabolized by both the 2'- and 5'-alpha-hydroxylation pathways. 2'-Hydroxylation of NNN produces the same DNA pyridyloxobutylating agent as does methyl hydroxylation of NNK. However, NNN is not a methylating agent and does not induce lung tumors in rats. Metabolism of NNN by 2'-hydroxylation was, depending on cell type, 41-85% as extensive as total alpha-hydroxylation of NNK, indicating that the rates of formation of the DNA pyridyloxobutylating agent were similar from NNN and NNK. The results of this study demonstrate that Clara cells have a high capacity to metabolically activate NNK, NNAL and NNN and provide further support for the hypothesis that DNA methylation of pulmonary cells is important in NNK carcinogenesis.

Alkylation↗
PubMed1989

Comparative tumorigenicity of 6-nitrochrysene and its metabolites in newborn mice.

The tumorigenic activities of 6-nitrochrysene and its metabolites were evaluated in the newborn mouse model. Groups of mice were treated with the appropriate compounds in DMSO by i.p. injections on the 1st, 8th and 15th day of life. Seven hundred nmol/mouse of 6-nitrochrysene induced significant incidences and multiplicities of lung tumors in both sexes; only males were susceptible to liver tumor induction. At 100 nmol/mouse, 6-nitrochrysene had significant tumorigenicity in both lung and liver but was less active than at the higher dose. Administration of 100 nmol/mouse of 6-nitrochrysene, only on day 1, caused about the same tumor yield as was observed after treatment with 700 nmol/mouse given over 3 days. Among the metabolites of 6-nitrochrysene which were tested at 100 nmol/mouse, 6-nitrosochrysene and 6-aminochrysene were significantly less active in the lung and in the liver than 6-nitrochrysene. In the lung, trans-1,2-dihydro-1,2-dihydroxy-6-nitrochrysene and trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene had activities comparable to those observed in mice treated with equimolar doses of 6-nitrochrysene. In the liver, trans-1,2-dihydro-1,2-dihydroxy-6-nitrochrysene was more active than 6-nitrochrysene based on the number of tumors per mouse. These observations support our hypothesis that 6-nitrochrysene is metabolically activated by ring-oxidation to trans-1,2-dihydro-1,2-dihydroxy-6-nitrochrysene, followed by nitro-reduction to trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene and, finally, oxidation to a diol-epoxide.

Animals↗
PubMed1989

Detection of cyclic 1,N2-propanodeoxyguanosine adducts in DNA of rats treated with N-nitrosopyrrolidine and mice treated with crotonaldehyde.

Cyclic 1,N2-propanodeoxyguanosine adducts are formed in vitro in DNA treated with alpha-acetoxy-N-nitrosopyrrolidine or its metabolite, crotonaldehyde. However, the in vivo formation of these cyclic adducts in DNA has not been demonstrated due to the lack of a sensitive detection method. In this study, a 32P-postlabeling method specific for the detection of 1,N2-propanodeoxyguanosine adducts was developed by using the corresponding 3'-monophosphates as standards. This method was validated by using DNA modified in vitro. It was then applied for the in vivo experiments in which hepatic DNA of rats treated with N-nitosopyrrolidine (NPYR) (total dose, 1.0 mmol) in drinking water or skin DNA of Sencar mice treated topically with crotonaldehyde (1.4 mmol) was isolated and subjected to 32P-postlabeling analysis. 1,N2-Propanodeoxyguanosine adducts were detected in these DNA samples. The minimal levels of adducts from liver DNA and skin DNA detected were estimated to be approximately 0.06 and approximately 0.24 mumol/mol guanine respectively. Interestingly, a background adduct spot chromatographically indistinguishable from the 1,N2-cyclic adducts was observed in the liver DNA of untreated rats. However, no such background adduct was detected in skin DNA of mice. This method demonstrated for the first time the in vivo formation of the cyclic 1,N2-propanodeoxyguanosine adducts.

Adenosine Triphosphate↗
PubMed1989

Evaluation of 32P-postlabeling analysis of DNA from exfoliated oral mucosa cells as a means of monitoring exposure of the oral cavity to genotoxic agents.

Development of oral cavity cancer in man has been linked to alcohol consumption and use of tobacco products. In order to understand the underlying carcinogenic mechanisms in the oral cavity a method is needed to monitor exposure of this site to various environmental insults. In this pilot study we evaluate the use of the 32P-postlabeling assay to detect adducts in DNA from exfoliated oral mucosa cells. Exfoliated cells were collected from the cheek and tongue of 27 men aged 35-69 years. DNA was extracted from the cells and analyzed by the enhanced 32P-postlabeling technique using butanol extraction. A variety of adduct spots were detected but none was consistently associated with exposure to alcohol or tobacco products. Some of the adducts detected had migration patterns in TLC very similar to the major deoxyguanosine adducts formed by the diol epoxides of benzo[a]pyrene and 5-methylchrysene, suggesting that they may have been formed from polynuclear aromatic hydrocarbons. Adduct spots with migration patterns similar to polynuclear hydrocarbon adducts accounted for only about one third of the total adduct spots observed. Relative adduct labeling (RAL) values were determined for samples from 12 of the 27 individuals. RAL values ranged from 1.6 X 10(-6) to 7.7 X 10(-11) adducts per nucleotide. The RAL values for adducts from the cheek or tongue were not significantly different. Adduct levels in smokers (median RAL of 4.8 X 10(-8) were significantly higher (P less than 0.001) than adduct levels in non-smokers (median RAL of 2.9 X 10(-9). Adduct levels in drinkers (median RAL of 9.1 X 10(-10) were significantly lower (P less than 0.001) than adduct levels in non-drinkers (median RAL of 3.7 X 10(-8). Four of the subjects in this study have subsequently developed squamous cell carcinoma of the oral cavity. 32P-Postlabeling analysis of DNA from the oral cavity of these subjects did not demonstrate unique patterns or RAL values. Lack of information on the structure of the majority of adducts observed in this study was a serious limitation. Further improvements in adduct identification will be needed before 32P-postlabeling can be a useful tool for monitoring exposure of the oral cavity to carcinogens.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1989

Comparative tumorigenicity of N-nitroso-2-hydroxymorpholine, N-nitrosodiethanolamine and N-nitrosomorpholine in A/J mice and F344 rats.

N-Nitroso-2-hydroxymorpholine (NHMOR), a genotoxic metabolite of the environmental carcinogens N-nitrosomorpholine (NMOR) and N-nitrosodiethanolamine (NDELA), was assayed for tumorigenicity in A/J mice and F344 rats. Groups of female mice were given NHMOR, NMOR or NDELA in the drinking water over a 10-week period; total doses were 53-55 mumol/mouse. The experiment was terminated after 30 weeks. Whereas NMOR was a potent tumorigen, inducing 20.3 lung tumors/mouse, NHMOR and NDELA were only weakly tumorigenic, giving 1.2 and 1.4 lung tumors/mouse respectively. Groups of female F344 rats were also given these three nitrosamines in drinking water for 50 weeks, as follows: NHMOR, total dose 0.6 mmol/rat; NHMOR, 1.2 mmol; NMOR, 1.1 mmol and NDELA, 5.6 mmol. The experiment was terminated after 120 weeks. NMOR was a potent carcinogen, inducing liver tumors in 100% of the rats. NDELA gave hepatocellular tumors in 70% of the rats. NHMOR was inactive even at the higher dose. The results of this study do not support the hypothesis that NHMOR is a proximate carcinogen of NDELA or NMOR.

Adenocarcinoma↗
PubMed1989

The effects of bay-region methyl substitution on 6-nitrochrysene mutagenicity in Salmonella typhimurium and tumorigenicity in newborn mice.

The mutagenic activities in Salmonella typhimurium and tumorigenic activities in newborn mice of 6-nitrochrysene (6-NC), 5-methyl-6-nitrochrysene (5-Me-6-NC), 11-methyl-6-nitrochrysene (11-Me-6-NC) and 5-methylchrysene (5-MeC) were compared. In S. typhimurium TA100 in the absence of rat liver 9000 g supernatant, 11-Me-6-NC was the most active compound followed by 6-NC; 5-Me-6-NC and 5-MeC were inactive. In the assays conducted in the presence of rat liver 9000 g supernatant, the order of activity was 11-Me-6-NC greater than 6-NC greater than 5-Me-6-NC approximately 5-MeC. In S. typhimurium TA98 a similar trend was observed. For the tumorigenicity studies, groups of mice were treated with the appropriate compounds in DMSO by i.p. injections on the 1st, 8th and 15th day of life. At a dose of 100 nmol/mouse 6-NC induced significantly more lung tumors than 5-MeC, which in turn was more active than 11-Me-6-NC and 5-Me-6-NC. All compounds induced significant numbers of liver tumors in treated males compared to controls; the order of activity was the same as that observed for lung tumor induction. The results of this study clearly indicate that bay region methyl substitution can either inhibit (5-position) or enhance (11-position) the mutagenic activity of 6-NC. In contrast, bay region methyl substitution (5- and 11-positions) inhibited the tumorigenic activity of 6-NC in newborn mice. Since ring oxidation and nitroreduction are involved in the metabolic activation of 6-NC in newborn mice, bay region methyl substitution may either inhibit the nitroreduction pathway or hinder the formation of the appropriate bay region diol epoxide. Steric factors may be important in determining the tumorigenicity of methylated nitrochrysenes.

Animals↗
PubMed1989

Effects of alkyl chain length on the inhibition of NNK-induced lung neoplasia in A/J mice by arylalkyl isothiocyanates.

Six homologous arylakyl isothiocyanates were evaluated for their abilities to inhibit pulmonary adenomas induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Four consecutive daily doses (5 mumol/mouse) of phenyl isothiocyanate (PITC), benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), 3-phenylpropyl isothiocyanate (PPITC), 4-phenylbutyl isothiocyanate (PBITC), 4-oxo-4-(3-pyridyl)-butyl isothiocyanate (OPBITC) and corn oil were administered to mice by gavage. Two hours following the final dosing, mice were administered saline or 10 mumol of NNK in saline i.p. Pulmonary adenomas were counted at 16 weeks after NNK administration. The mice administered only corn oil prior to NNK developed an average multiplicity of 9.2 tumors/mouse. Pretreatment with PITC, BITC and OPBITC had no significant effects on NNK-induced lung neoplasia. However, PEITC pretreatment resulted in a 64% reduction of lung tumor multiplicity, but did not affect the percentage of mice that developed tumors. Both PPITC and PBITC decreased tumor multiplicity by 96% and the percentage of tumor-bearing animals by greater than 60%. These results, in conjunction with our previous work, demonstrate a general trend of increasing inhibition of NNK-induced lung neoplasia by arylalkyl isothiocyanates with increasing alkyl chain length. This study also demonstrates the remarkable inhibitory activities of PPITC and PBITC, two isothiocyanates that had not previously been tested as chemopreventive agents.

Adenoma↗
PubMed1989

Mutagenicity, metabolism and DNA adduct formation of 6-nitrochrysene in Salmonella typhimurium.

The mutagenic activities of 6-nitrochrysene (6-NC) and its previously identified metabolites were evaluated in Salmonella typhimurium TA100 and TA98 in the presence and absence of metabolic activation by 9000 g supernatant from the livers of rats treated with Aroclor. 6-Aminochrysene (6-AC) and trans-1,2-dihydro-1,2-dihydroxy-6-aminochrysene (1,2-DHD-6-AC) were the most active mutagens in TA100 upon metabolic activation. 6-NC and 6-AC were the most active mutagens in TA100 in the absence of metabolic activation. Upon metabolic activation, 6-AC was the most active in TA98; the other compounds were weak or inactive depending on the conditions of the assay. In the absence of metabolic activation, the mutagenic activities of 6-NC and its metabolites in TA98 were comparable to those observed in TA100. The major metabolite formed upon incubation of [3H]6-NC with S.typhimurium TA100 and 9000 g supernatant from the livers of Aroclor-induced rats was identified as trans-1,2-dihydro-1,2-dihydroxy-6-nitrochrysene (1,2-DHD-6-NC); trans-9,10-dihydro-9,10-dihydroxy-6-nitrochrysene and 1,2-dihydroxy-6-nitrochrysene were also identified. The major DNA adduct formed in TA100 under these conditions was chromatographically identical to that previously detected in vivo in the liver and lungs of newborn mice treated with 6-NC, as well as to that obtained upon incubation of 1,2-DHD-6-AC with calf thymus DNA in the presence of rat liver microsomes. The DNA adducts derived from 6-NC in S.typhimurium TA100 without activation were identical to those adducts previously identified after incubation of 6-hydroxylaminochrysene with calf thymus DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Mechanistic studies of tobacco carcinogenesis in mouse epidermis and lung tissues.

The particulate matter of tobacco smoke induces benign and malignant tumors in various animal tissues and species. The most widely used bioassay system for evaluating the carcinogenicity of tobacco tars is mouse skin. Mouse skin bioassays have led to the identification of the PAHs as the major tumor initiators, while showing that catechols are important cocarcinogens in tobacco smoke. Mechanistic studies suggest that catechol affects BaP metabolism and especially secondary oxidation reactions of this carcinogen and thus changes the proportion of BPDE-DNA adducts. Comparison of the disposition and metabolism of BaP and its ultimate carcinogenic derivative, anti-BPDE, in mouse epidermis demonstrates that the lower activity of BPDE relative to BaP in mouse skin is partially due to differences in penetration and trapping of BPDE within the epidermis, where it is protected from hydrolysis and reaction with intracellular macromolecules. Although screening for tumorigenicity on mouse skin is limited to the detection of certain classes of carcinogens and is not helpful for the evaluation of organ-specific carcinogens, mouse skin assays of cigarette smoke condensates have nevertheless served as valuable indicators of the tumorigenic potential of tobacco smoke for epithelial tissues.

Animals↗
PubMed1988

Induction of lung and exocrine pancreas tumors in F344 rats by tobacco-specific and Areca-derived N-nitrosamines.

The tobacco-specific N-nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), as well as the Areca-derived N-nitrosoguvacoline (NG) were assayed for carcinogenicity in male F344 rats by lifetime administration in the drinking water. Groups of 30 to 80 rats were treated with 0.5 ppm, 1.0 ppm, or 5.0 ppm of NNK; 5.0 ppm of NNAL, 20 ppm of NG, a mixture of 20 ppm of NG and 1 ppm of NNK, and water only in the control group. The approximate total doses of the nitrosamines (mmol/kg of body weight) in these groups were: NNK, 0.073, 0.17, and 0.68; NNAL, 0.69; NG, 4.1; NG and NNK, 4.1 and 0.17. As in previous assays in which NNK was tested by s.c. injection, the lung was its principle target organ. Lung tumor incidences in the 0.5-, 1.0-, and 5.0-ppm groups were nine of 80, 20 of 80, and 27 of 30 compared to six of 80 in the control rats. This trend was significant, P less than 0.005. Significant incidences of nasal cavity and liver tumors were observed only in the rats treated with 5.0 ppm of NNK. In contrast to the results of the s.c. bioassays of NNK, tumors of the exocrine pancreas were observed in five of 80 and nine of 80 rats treated with 0.5 and 1.0 ppm. This trend was significant, P less than 0.025. This is the first example of pancreatic tumor induction by a constituent of tobacco smoke. It is also the first finding of duct-like carcinomas in the rat pancreas, including one tumor containing epidermoid, keratin-generating tissue. NNAL, the major metabolite of NNK, induced lung tumors in 26 of 30 rats and pancreatic tumors in eight of 30 rats. It appears to be the proximate pancreatic carcinogen of NNK. NG induced pancreatic tumors in four of 30 rats, P less than 0.05. This finding requires confirmation. The mixture of NG and NNK induced lung tumors in eleven of 30 rats. There were no apparent synergistic interactions of NG and NNK. The observation of benign and malignant tumors of the lung and pancreas of rats treated with the tobacco-specific nitrosamines NNK and NNAL is discussed in respect to the causal association between cigarette smoking and cancer of the lung and pancreas.

Animals↗
PubMed1988

Detection of O6-methyldeoxyguanosine in human placental DNA.

A monoclonal antibody specific for O6-methyldeoxyguanosine (O6-MedGuo) was developed. When used in a competitive enzyme-linked immunosorbent assay, 50% inhibition of binding was achieved with 0.51 pmol O6-MedGuo. When the competitive enzyme-linked immunosorbent assay was coupled with high-performance liquid chromatography, 2 mg of DNA could be analyzed giving a lower limit of detection of 0.5 mumol O6-MedGuo/mol deoxyguanosine. This assay was used to test for O6-MedGuo in DNA from placentas of smoking and nonsmoking women. Two of 10 DNA samples from smoking women and three of 10 from nonsmoking women had detectable concentrations of O6-MedGuo. Concentrations ranged from 0.6 to 1.6 mumol O6-MedGuo/mol deoxyguanosine. Activity of O6-alkylguanine DNA alkyltransferase was also measured. There was no apparent relationship between O6-alkylguanine DNA alkyltransferase activity and O6-MedGuo concentrations in the 20 subjects, nor did mean O6-alkylguanine DNA alkyltransferase activity differ between the two groups. Although no apparent relationship between smoking history and O6-MedGuo concentration was found in this preliminary study, this is the first report of a structurally identified DNA adduct in human placenta.

Antibodies, Monoclonal↗
PubMed1988

Comparative tumorigenicity of 1-nitropyrene, 1-nitrosopyrene, and 1-aminopyrene administered by gavage to Sprague-Dawley rats.

The carcinogenic activities of 1-nitropyrene, a mutagenic component of diesel exhaust, and its reduced derivatives 1-nitrosopyrene and 1-aminopyrene were evaluated in male and female Sprague-Dawley rats. Within 24 h of birth, groups of 22-36 rats were treated by gavage with trioctanoin or the appropriate compound in trioctanoin once weekly for 16 weeks. The approximate total doses per rat were as follows: 1-nitropyrene, high dose (800 mumol); 1-nitropyrene, low dose (320 mumol); 1-nitrosopyrene (320 mumol); 1-aminopyrene (320 mumol). The experiment was terminated after 94 weeks. The main site of tumor induction was the mammary glands of female rats. Percentages of incidences of mammary adenocarcinomas in female rats were as follows: 1-nitropyrene, high dose (63%); 1-nitropyrene, low dose (42%); 1-nitrosopyrene (19%); 1-aminopyrene (4%) trioctanoin (3%). These incidences were significantly greater than those of controls for the female rats treated with either 1-nitropyrene or 1-nitrosopyrene. Low and generally insignificant incidences of tumors of a variety of other sites were also observed in rats treated with 1-nitropyrene. The induction of mammary tumors by 1-nitropyrene confirms the results of a previous study (Hirose et al., Cancer Res., 44: 1158-1162, 1984). The present results also demonstrate that, under the conditions of this bioassay, 1-nitropyrene was significantly more carcinogenic than either 1-nitrosopyrene or 1-aminopyrene.

Adenocarcinoma↗
PubMed1988

Reactivity with DNA bases and mutagenicity toward Salmonella typhimurium of methylchrysene diol epoxide enantiomers.

The reactions with DNA and mutagenic activities toward Salmonella typhimurium TA 100 of the R,S,S,R and S,R,R,S enantiomers of anti-1,2,-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5-methylchrysene (anti-5-MeC-1,2-diol-3,4-epoxide), anti-5-MeC-7,8-diol-9,10-epoxide, and anti-6-MeC-1,2-diol-3,4-epoxide were compared because among these compounds only the R,S,S,R enantiomer of anti-5-MeC-1,2-diol-3,4-epoxide is highly tumorigenic. The major products formed in the reaction of each racemic diol epoxide with DNA were two pairs of deoxyguanosine (dGuo) and deoxyadenosine (dAdo) adducts; one product in each pair was formed from the R,S,S,R enantiomer and the other from the S,R,R,S enantiomer of each racemic diol epoxide. Formation of products from R,S,S,R enantiomers exceeded formation of those from S,R,R,S enantiomers in each case. Among the R,S,S,R enantiomers, 5-MeC-1,2-diol-3,4-epoxide, which has a methyl group in the same bay region as the epoxide ring, was most reactive toward DNA, and in particular toward dGuo. The dGuo/dAdo adduct ratios were greater for the products formed from the R,S,S,R enantiomer compared to the S,R,R,S enantiomer of each diol epoxide. The dGuo/dAdo adduct ratios were also greater for the enantiomers of anti-5-MeC-1,2-diol-3,4-epoxide than for the enantiomers of either anti-5-MeC-7,8-diol-9,10-epoxide or anti-6-MeC-1,2-diol-3,4-epoxide. In S. typhimurium TA 100, the R,S,S,R enantiomer of anti-5-MeC-1,2-diol-3,4-epoxide was the most mutagenic compound (6700 revertants/nmol), followed by the R,S,S,R enantiomer of anti-5-MeC-7,8-diol-9,10-epoxide (1500 revertants/nmol). The other diol epoxide enantiomers were weakly active or inactive at the doses tested. The results of this study demonstrate that both the absolute configuration of a diol epoxide and the position of the methyl group have major effects on its reactivity with DNA. The greatest reactivity is seen in an R,S,S,R enantiomer with the methyl group and epoxide ring in the same bay region, e.g., the highly tumorigenic and mutagenic 5-MeC-1R,2S-diol-3S,4R-epoxide. Comparison of the dGuo/dAdo adduct ratios of the various diol epoxides with their tumorigenic and mutagenic activities suggests that dGuo adducts are important in the expression of biological activity of methylchrysene diol epoxides.

Chemical Phenomena↗
PubMed1988

Evidence for 4-(3-pyridyl)-4-oxobutylation of DNA in F344 rats treated with the tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine.

DNA was isolated from tissues of F344 rats 24 h after treatment by s.c. injection with [5-3H]4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone ([5-3H]NNK) or [5-3H]N'-nitrosonornicotine ([5-3H]NNN). It was hydrolyzed with acid or at pH 7, 100 degrees C, and the hydrolysates were analyzed by HPLC. The major product in each case was identified as 4-hydroxy-1-(3-pyridyl)-1-butanone, formed by hydrolysis of a DNA adduct. It was detected in DNA from the livers of rats treated with [5-3H]NNK or [5-3H]NNN, and in DNA from lungs of rats treated with [5-3H]NNK. These results demonstrate that 4-(3-pyridyl)-4-oxobutylation of DNA occurs in rats treated with NNK or NNN, and are consistent with the hypothesis that these nitrosamines are metabolically activated by alpha-hydroxylation.

Animals↗
PubMed1988

Metabolism of the carcinogen [3H]6-nitrochrysene in the preweanling mouse: identification of 6-aminochrysene-1,2-dihydrodiol as the probable proximate carcinogenic metabolite.

6-Nitrochrysene (NC) is a potent lung and liver carcinogen when administered in multiple doses to preweanling mice. We have investigated both the in vitro metabolism of [3H]NC by 9000 g supernatants (S9) prepared from the livers of preweanling mice and the in vivo metabolism of [3H]NC in these animals. The in vitro covalent binding of primary metabolites of NC to DNA after further reductive and/or oxidative metabolism was then examined in an attempt to define the metabolic activation pathway responsible for the formation of carcinogen--DNA adducts in NC-treated preweanling mice. NC-1,2-dihydrodiol, NC-9,10-dihydrodiol, 6-aminochrysene (AC), and several unidentified compounds were found in ethyl acetate extracts of incubations containing [3H]NC and liver S9 from 1- or 8-day-old BLU:Ha mice. Comparison of the in vivo metabolism of NC in 1-day-old animals and 8-day-old animals which had been treated with NC on day 1 indicated that the formation of AC and the two NC dihydrodiols was greater in the younger animals. Further metabolism of NC-1,2-dihydrodiol by S9 from 8-day-old mice yielded AC-1,2-dihydrodiol as a major product. Incubation of AC-1,2-dihydrodiol, calf thymus DNA and liver microsomes from 3-methylcholanthrene-induced rats yielded a single major adduct that was chromatographically and chemically identical to the major adduct formed in [3H]NC- and [3H]-AC-treated preweanling mice. The results indicated that the major DNA adduct found in vivo is derived from the further metabolism of the proximate carcinogen AC-1,2-dihydrodiol.

Animals↗
PubMed1988

Effects of dietary sinigrin or indole-3-carbinol on O6-methylguanine-DNA-transmethylase activity and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced DNA methylation and tumorigenicity in F344 rats.

The effects of dietary sinigrin and indole-3-carbinol (I3C) on DNA methylation and O6-methylguanine--DNA-transmethylase activity, factors which may be of importance in the induction of tumorigenicity by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), were investigated. Additionally, the effects of dietary sinigrin on NNK tumorigenicity were assessed in a two-year bioassay in F344 rats. DNA methylation in target tissues of NNK tumorigenesis was examined in F344 rats administered [3H-CH3]NNK (0.6 mg/kg, four doses) s.c. and fed control or experimental diets for two weeks. Dietary sinigrin at a concentration of 3 mumol/g diet decreased 7-methylguanine formation in hepatic DNA, but had no effect on 7-methylguanine levels of lung or nasal mucosa DNA. Dietary I3C at a concentration of 30 mumol/g diet increased 7-methylguanine levels in hepatic DNA, but decreased DNA methylation in lung and nasal mucosa. No effects on O6-methylguanine--DNA-transmethylase activity were observed in tissue extracts derived from the livers, lungs and nasal mucosae of rats fed diets containing sinigrin or I3C. These results suggested that dietary sinigrin might reduce the incidence of NNK-induced hepatic tumors with no effect on NNK tumorigenesis of the lung and nasal cavity, whereas I3C might increase hepatic tumor incidence and reduce NNK tumorigenesis of the lung and nasal cavity. The bioassay results showed that dietary sinigrin had no effect on NNK tumorigenesis in these target tissues. However, dietary sinigrin plus NNK resulted in a significant incidence of pancreatic tumors, a rare occurrence in F344 rats. While the results from DNA methylation studies are in agreement with the bioassay data for lung and nasal cavity, the absence of any inhibitory effect of dietary sinigrin on NNK hepatic tumorigenesis indicates that factors other than DNA methylation and O6-methylguanine repair should be considered in assessing the effects of dietary compounds on NNK hepatic tumorigenesis. The contrary effects on NNK-induced hepatic DNA methylation by sinigrin and I3C, two major components of cruciferous vegetables, demonstrate the complexities of dietary modulation of carcinogenesis.

Animals↗