Biomedical subjects

S S Hecht

Publications and source records attributed to S S Hecht.

At least 361 records · Page 20Linked to original sources

PubMedDate not supplied

Formation of acyclic and cyclic guanine adducts in DNA reacted with alpha-acetoxy-N-nitrosopyrrolidine.

This paper describes the reaction of alpha-acetoxy-N-nitrosopyrrolidine with DNA to produce six adducts: two new acyclic adducts, 7-(4-oxobutyl)guanine (6) and 7-(3-carboxypropyl)guanine (7), and four cyclic adducts--the exocyclic 7,8-guanine adducts 5, 11, and 12 and an exocyclic 1,N2-guanine adduct 13--which we have previously characterized. The initial purpose of this study was to carry out an independent synthesis to verify the structure of adduct 5, which is formed in liver DNA of rats treated with N-nitrosopyrrolidine. This was accomplished by the reaction of 2',3',5'-triacetylguanosine with 4-iodobutyraldehyde. This reaction also produced 7-(4-oxobutyl)guanine (6), which underwent air oxidation to 7. The new adducts were characterized by their proton NMR, UV, and mass spectral properties, by chemical transformations, and by independent syntheses. The six adduct standards were used to develop HPLC systems for their analysis as products of the reaction of alpha-acetoxy-N-nitrosopyrrolidine with DNA. Studies on their rates of formation and stability in DNA were carried out. The major products were 7-(4-oxobutyl)guanine (6) and the exocyclic 7,8-guanine adduct 5, which apparently were both formed mainly by reaction with DNA of 4-oxobutanediazohydroxide (4). Their concentrations were maximal after 6 h and subsequently decreased due to depurination. Little evidence was obtained for cyclization of 6 to 5, at the base level or in DNA. The concentrations of adducts 11-13, which were formed by reaction with DNA of crotonaldehyde (10), increased gradually over the 36-h time period studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Modulation of benzo[a]pyrene-DNA adducts in hamster cheek pouch by chronic ethanol consumption.

The effects of chronic ethanol consumption by hamsters on the binding of [3H]benzo[a]pyrene (BaP) metabolites to the DNA of cheek pouch and liver have been examined. Thirty hamsters were fed control liquid diet, and another 30 hamsters were given 6.6% v/v, 190 proof ethanol-containing diet for 28 days. Twenty-four hours after topical application of [3H]BaP to the cheek pouches, the hamsters were killed and DNA was isolated from epithelial sheets of the cheek pouches and from the liver. Two major deoxyribonucleoside adducts were detected in the hamster cheek pouch; one was identified as the N2-deoxyguanosine adduct of (+)-[3H]-7 alpha,8 beta-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydro- BaP [(+)-anti-BPDE-dG]. The other has not yet been characterized. It was named adduct A and cochromatographed with the major adduct derived from (+)-[3H]-trans-7,8-dihydroxy-7,8- dihydrobenzo[a]pyrene [(+)-BaP-7,8-diol] in mouse skin. Chronic ethanol consumption by hamsters had no statistically significant effect on the (+)-anti-BPDE-dG adduct whereas it increased the level of adduct A by 80%. Binding of BaP metabolites to liver DNA was minor and was not influenced by ethanol. This study suggests that chronic ethanol consumption by hamsters either enhances the formation of the (+)-BaP-7,8-diol from BaP or increases oxidation of this diol and its binding to the DNA of the hamster's cheek pouch.

Alcoholism↗

PubMedDate not supplied

Solvolysis of model compounds for alpha-hydroxylation of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: evidence for a cyclic oxonium ion intermediate in the alkylation of nucleophiles.

N'-Nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), two potent tobacco-specific carcinogens, have been previously found to pyridyloxobutylate DNA. The adducts were found to be unstable and have not been fully characterized. In order to gain an understanding of the chemistry of the pyridyloxobutylating species, five model pyridyloxobutylating agents have been solvolyzed and the products identified. 4-[(Acetoxymethyl)-nitrosamino]-1-(3-pyridyl)-1-butanone (3), 4-(carbethoxynitrosamino)-1-(3-pyridyl)-1-butanone (4), 4-oxo-4-(3-pyridyl)-1-butyl p-toluenesulfonate (16), 2-chloro-2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (17), and 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanol (20) were solvolyzed in buffer and in buffer containing 20% MeOH. The solvolyses of 16 and 17 in H2O produced only 4-hydroxy-1-(3-pyridyl)-1-butanone (7). In the presence of 20% MeOH, 7 and 2-methoxy-2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (12) were produced from 16 and 17 in a 4:1 ratio. The solvolysis of 3 and 4 in the presence of esterase gave similar products. 4-Methoxy-1-(3-pyridyl)-1-butanone (8) was not detected as a product. In the absence of MeOH, compound 7, 3-pyridyl cyclopropyl ketone (10), and 1-(3-pyridyl)-but-2-en-1-one (18) were observed. In the presence of MeOH, 12 was also formed and the ratio of 7 to 12 was again about 4:1. The esterase-catalyzed hydrolysis of 20 yielded 1-(3-pyridyl)-1,4-butanediol (22), 1-(3-pyridyl)-1,3-butanediol (27), 1-(3-pyridyl)-but-3-en-1-ol (25), 1-(3-pyridyl)but-2-en-1-ol (26), and 2-(3-pyridyl)-2,3,4,5-tetrahydrofuran (24).(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗

PubMedDate not supplied

Mass spectrometric analysis of tobacco-specific nitrosamine-DNA adducts in smokers and nonsmokers.

A gas chromatography, negative ion chemical ionization mass spectrometry (GC-NICI-MS) based assay for tobacco-specific nitrosamine adducts of DNA is described. The assay is based on the observation that acid hydrolysis of DNA from animals treated with tobacco-specific nitrosamines releases 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB). HPB and the internal standard [4,4-D2]HPB are derivatized with pentafluorobenzoyl chloride and the resulting HPB-pentafluorobenzoate is purified by high-performance liquid chromatography prior to GC-NICI-MS analysis. DNA from human peripheral lung and tracheobronchial tissue, collected at autopsy, was analyzed for acid-released HPB. The mean HPB level (fmol/mg of DNA) for peripheral lung DNA was 11 +/- 16 (SD, n = 9) for smokers and 0.9 +/- 2.3 (n = 8) for nonsmokers. Mean adduct levels in tracheobronchus were 16 +/- 18 (n = 4) for smokers and 0.9 +/- 1.7 (n = 4) for nonsmokers. These are the first measurements of tobacco-specific nitrosamine-DNA adducts in humans. Further studies comparing the levels of DNA and globin adducts will provide a better understanding of the metabolic activation of tobacco-specific nitrosamines in humans and may provide a more accurate indication of an individual's risk of developing tobacco-related cancer.

Adolescent↗

PubMedDate not supplied

Evidence that a hemoglobin adduct of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is a 4-(3-pyridyl)-4-oxobutyl carboxylic acid ester.

Hemoglobin adducts of the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) release 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) upon mild base or acid hydrolysis. HPB has been detected in hydrolysates of human hemoglobin and has been proposed as a dosimeter of exposure to and metabolic activation of NNK in people exposed to tobacco products. In this study, labeling experiments were carried out with Na18OH which provide strong evidence that the globin adduct which releases HPB upon base hydrolysis is a carboxylic acid ester. Globin was isolated from rats treated with NNK. This globin was reacted with NaCNBH3, followed by hydrolysis at room temperature with 0.2 N NaOH. Analysis of the products demonstrated the presence of 4-hydroxy-1-(3-pyridyl)-1-butanol (7), but not HPB. These results demonstrate that the adduct in globin has a free carbonyl group and is not a Schiff base. This sequence of reactions was then carried out with Na18OH, under conditions which would have resulted in incorporation of 18O into 7 if nucleophilic displacement at carbon 4 of the adduct had occurred. Analysis of the products by GC-MS showed no detectable incorporation of 18O into 7. These results demonstrate that the globin adduct which releases HPB upon base hydrolysis is a 4-(3-pyridyl)-4-oxobutyl carboxylic ester. Consistent with this conclusion, a model ester, alpha-methyl beta-[4-(3-pyridyl)-4-oxobutyl] N-(carbobenzyloxy)-L-aspartate (13), hydrolyzed in base and acid in a manner similar to that observed with globin from NNK-treated rats.

Animals↗

PubMedDate not supplied

Comparative tumorigenicity of dimethylchrysenes in mouse skin.

In previous studies, we have observed unexpected structure-tumorigenicity relationships among the dimethylchrysenes. Thus, 5,6-dimethylchrysene and 5,7-dimethylchrysene were only weakly tumorigenic and were significantly less active than 5-methylchrysene. These results were surprising in view of the known route of metabolic activation of 5-methylchrysene via its 1,2-diol 3,4-epoxide. In this paper, we extended our studies of structure-tumorigenicity relationships among the dimethylchrysenes. We synthesized 5,7-, 5,8-, 5,9-, and 5,10-dimethylchrysene via photochemical ring closure reactions. The tumor-initiating activities of these dimethylchrysenes on mouse skin were compared with those of 5-methylchrysene and 5,6-dimethylchrysene. 5-Methylchrysene and 5,9-dimethylchrysene were highly tumorigenic and were significantly more active than 5,6-, 5,7-, 5,8-, and 5,10-dimethylchrysene. The results of these studies, taken together with those reported in the subsequent two papers, suggest that the molecular shapes of dimethylchrysenes influence the balance between metabolic activation and detoxification pathways.

Animals↗

PubMedDate not supplied

Metabolism and DNA binding of 5,6-dimethylchrysene in mouse skin.

5,6-Dimethylchrysene (5,6-diMeC) is a weaker tumor initiator on mouse skin than 5-methylchrysene (5-MeC). To investigate the reasons for the unexpectedly low activity of 5,6-diMeC, we have studied its metabolism and DNA binding in mouse skin, particularly with respect to metabolic activation via its anti-1,2-diol 3,4-epoxide. The metabolism of 5,6-diMeC was first examined with liver 9000g supernatant from Aroclor 1254 pretreated rats. Three major metabolites were identified as 1- or 7-hydroxy-5-(hydroxymethyl)-6-MeC, 1,2-dihydroxy-1,2-dihydro-5,6-diMeC (5,6-diMeC-1,2-diol), and 1-hydroxy-5,6-diMeC. The formation of 5,6-diMeC-1,2-diol was then assessed in mouse epidermis, following topical application of [3H]5,6-diMeC. Levels of 5,6-diMeC-1,2-diol in epidermis exceeded those of 5-MeC-1,2-diol formed from 5-MeC under similar conditions. The binding of [3H]5,6-diMeC and that of [3H]5-MeC to mouse epidermal DNA were then compared. 5,6-DiMeC-deoxyribonucleoside adducts were prepared as markers by reaction of anti- and syn-5,6-diMeC-1,2-diol 3,4-epoxide with calf thymus DNA. HPLC analysis of enzymatic hydrolysates of mouse epidermal DNA, isolated 18 h after topical treatment with [3H]5,6-diMeC or [3H]5-MeC, demonstrated the formation from [3H]5,6-diMeC of two major adducts produced by reaction of its anti-1,2-diol 3,4-epoxide with deoxyguanosine and deoxyadenosine, respectively, while the major adduct formed from [3H]5-MeC resulted from reaction with deoxyguanosine, in agreement with previous results. Total DNA binding of [3H]5-MeC as well as formation of deoxyguanosine adducts exceeded that of [3H]5,6-diMeC by 3-4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Dimethylchrysene diol epoxides: mutagenicity in Salmonella typhimurium, tumorigenicity in newborn mice, and reactivity with deoxyadenosine in DNA.

In contrast to 5-methylchrysene and 5,9-dimethylchrysene, 5,6-dimethylchrysene and 5,7-dimethylchrysene are weak tumor initiators on mouse skin. In order to investigate the basis for this, we have evaluated the mutagenic activities toward Salmonella typhimurium TA 100 and reactivity with DNA of (+/-)-anti-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5,6-dimethyl-ch rys ene (anti-5,6-diMeC-1,2-diol 3,4-epoxide) and anti-5,7- and anti-5,9-diMeC-1,2-diol 3,4-epoxide. The tumorigenic activities of anti-5,6- and anti-5,7-diMeC-1,2-diol 3,4-epoxides in newborn mice were also investigated. anti-5,9-diMeC-1,2-diol 3,4-epoxide was the most mutagenic of the three diol epoxides. anti-5,6-diMeC-1,2-diol 3,4-epoxide was highly tumorigenic in newborn mouse lung, with activity significantly greater than that of either anti-5-MeC- or anti-5,7-diMeC-1,2-diol 3,4-epoxide. Although the amounts of total binding of the diol epoxides to calf thymus DNA were similar, anti-5,6-diMeC-1,2-diol 3,4-epoxide bound extensively to deoxyadenosine residues. High binding to deoxyadenosine is related to the presence of a sterically hindered bay or fjord region as present in 5,6-diMeC, 7,12-dimethylbenz[a]anthracene, benzo-[g]chrysene, and benzo[c]phenanthrene. The conformations of the anti- and syn-diol epoxides of 5,6-diMeC and benzo[c]phenanthrene were similar, with both having pseudodiequatorial hydroxyl groups, in contrast to less sterically crowded diol epoxides. The high tumorigenicity of anti-5,6-diMeC-1,2-diol 3,4-epoxide in newborn mice is of interest with respect to its high deoxyadenosine binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone pulmonary metabolism and tumorigenicity in mice by analogues of the investigational chemotherapeutic drug 4-ipomeanol.

4-Ipomeanol (IPO) is an investigational chemotherapeutic drug with specific toxicity toward the lung. It is metabolically activated to reactive intermediates by cytochrome P450 enzymes present in Clara cells. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a highly carcinogenic tobacco-specific nitrosamine with organo-specificity for the lung. Like IPO, which it resembles structurally, it is metabolically activated by cytochrome P450 enzymes of rat Clara cells. We synthesized nontoxic analogues of IPO and tested their activities as inhibitors of the metabolism and tumorigenicity of NNK. The IPO analogues synthesized were 4-hydroxy-1-phenyl-1-pentanone (HPP), 7-hydroxy-1-phenyl-1-octanone (HPO), 4-hydroxy-1-(2-thienyl)-1-pentanone (HTP), and 4-hydroxy-1-(3-pyridyl)-1-pentanone (HPYP). When added to A/J mouse lung microsomal incubations, all compounds significantly inhibited the oxidative pathways of NNK metabolism--alpha-hydroxylation and pyridine N-oxidation--to varying extents. Inhibition of carbonyl reduction of NNK was generally less effective. Inhibition of alpha-hydroxylation by IPO, HPP, and HTP was more pronounced in incubations with lung microsomes than with liver microsomes. None of the IPO analogues showed significant toxicity when given to A/J mice at a dose of 25 mumol; IPO itself was lethal at this dose. HPP and HPO, at doses of 25 mumol, significantly inhibited lung tumor multiplicity in mice treated with NNK; the other analogues and IPO itself were ineffective. The results of this study provide new leads for development of inhibitors of NNK metabolism and chemical probes for the active site of P450 enzymes in Clara cells.

Animals↗

PubMedDate not supplied

Reaction of alpha-acetoxy-N-nitrosopiperidine with deoxyguanosine: oxygen-dependent formation of 4-oxo-2-pentenal and a 1,N2-ethenodeoxyguanosine adduct.

The six-membered heterocyclic nitrosamine N-nitrosopiperidine (NPIP) is an esophageal carcinogen in the rat whereas its five-membered homologue N-nitrosopyrrolidine (NPYR) is a liver carcinogen. These contrasting organo-specificities may be due to differences between NPIP and NPYR in their metabolic activation to intermediates which bind to DNA. Previous studies have shown that the metabolic activation of NPYR to DNA binding products occurs through alpha-hydroxylation. DNA adducts of NPIP have not been characterized. Therefore, we began our studies by investigating the reaction of alpha-acetoxyNPIP with deoxyguanosine. A major adduct, detected by high-performance liquid chromatography with UV detection, was characterized by its UV, 1H-NMR, and MS as 7-(2-oxopropyl)-5,9-dihydro-9-oxo-3-beta-D-deoxyribofuranosylimidazo+ ++[1,2-a] purine. This 7-(2-oxopropyl)-substituted 1,N2-ethenodeoxyguanosine adduct was formed by reaction of 4-oxo-2-pentenal (3-acetylacrolein) with the 1 and N2 positions of deoxyguanosine. Since the formation of 4-oxo-2-pentenal from alpha-acetoxyNPIP was unexpected, we investigated the solvolysis of alpha-acetoxyNPIP in more detail. Major products formed in incubations of alpha-acetoxyNPIP for 7-24 h in phosphate buffer (pH 7.0) at 37 degrees C included 4-oxo-2-pentenal (11-21% yield), 4-hydroxypentanal (18-22%), and 5-hydroxypentanal (27-29%). The formation of 4-oxo-2-pentenal required O2. The results of this study demonstrate some unique features of the chemistry of alpha-acetoxyNPIP and the resulting deoxyguanosine adducts which may be related to the carcinogenic activity of NPIP.

Acrolein↗

PubMedDate not supplied

Distinct conformers of alkylchrysene diol epoxide-deoxyguanosine adducts detected by proton NMR.

Proton NMR spectra, obtained in MeOH-d4, of the major DNA adduct of 5,7-dimethylchrysene-1,2-diol 3,4-epoxide, identified as 1(R),2(S),3(S)-trihydroxy-4(S)-(N2-deoxyguanosyl)-1, 2,3,4-tetrahydro-5,7-dimethylchrysene, showed the presence of two distinct conformers. One conformer, similar to those observed previously in spectra of peracetates of related DNA adducts of anti-diol epoxides of polynuclear aromatic hydrocarbons, had a chair-like conformation of the tetrahydrobenzo ring. The other conformer, which has not been previously observed, had a boat-like conformation of the tetrahydrobenzo ring. This conformer was converted to the chair-like conformer upon addition of D2O or trifluoroacetic acid to the MeOH-d4 solutions of the adduct. The new conformers were also observed in proton NMR spectra of major DNA adducts of 5-methylchrysene- and 5,6-dimethylchrysene-1,2-diol 3,4-epoxides.

Carcinogens↗

PubMedDate not supplied

Synthesis of N-(purin-8-yl)arylamines.

Methods for direct synthesis of N-(purin-8-yl)arylamines were investigated. N-(Purin-8-yl)arylamines are adducts from reaction of electrophilic metabolites of arylamines with DNA and have not been readily available by direct synthesis. Ability to generate significant quantities of this class of DNA adduct by synthetic means would facilitate basic research in molecular toxicology. Two routes with common thiourea intermediates were developed for this purpose. In the first route, 6-hydroxy-2,4,5-triaminopyrimidine was caused to react in aqueous medium with dithiocarbamate derivatives of o-, m-, or p-toluidine to form corresponding 2,4-diamino-5-(tolylthioureido)aminopyrimidin-6-ones in 60-70% yields. The thiourea intermediates were converted to carbodiimides and isolated in 20-25% yields after treatment with HgO in dimethylformamide. The carbodiimides were cyclized at 125 degrees C in dimethylformamide under N2 for 45 h to yield N-(guanin-8-yl)(o-, m-, or p-)toluidines in 65-75% yields. In the second route, direct reaction of p-tolyl isothiocyanate with 6-hydroxy-2,4,5-triaminopyrimidine or with 4,5,6-triaminopyrimidine in dimethylformamide and triethylamine led to the formation of 2,4-diamino-5-(p-tolylthioureido)aminopyrimidin-6-one and 4,6-diamino-5-(tolylthioureido)aminopyrimidine, respectively, in 77-79% yields. Methylation of the two thiourea derivatives by methyl iodide in dimethylformamide gave the corresponding methylisothiuronium derivatives, which were isolated in 71% and 84% yields (as HI salts), respectively. Conversion of the methylisothiuronium derivatives to N-(guanin-8-yl)-p-toluidine or N-(adenin-8-yl)-p-toluidine was accomplished by heating in dimethylformamide for 5-7 h at 80-90 degrees C, in 70% and 62% yields, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinogens↗

PubMedDate not supplied

Unwinding and hydrodynamic flow linear dichroism characteristics of supercoiled DNA covalently modified with two isomeric methylchrysene diol epoxides of different biological activities.

Adducts derived from the covalent binding of two positional monomethyl-substituted isomers of a bay region chrysene diol epoxide to supercoiled pIBI30 DNA (2926 base pairs/genome) were prepared, and their characteristics were investigated by a combination of gel electrophoresis and flow linear dichroism techniques. The 5- and 6-methyl derivatives of trans-1,2-dihydroxy-anti-3,4-epoxy-1,2,3,4-tetrahydrochrysene [(+)-5- and (+)-6-MeCDE, respectively], both with 1R,2S,3S,4R stereochemistry, are characterized by significant differences in their biological activities [Melikian et al. (1988) Cancer Res. 48, 1781-1787]. When covalently bound to plasmid DNA, these two molecules give rise to striking differences in the gel electrophoretic and flow hydrodynamic characteristics of the modified supercoiled DNA. The hydrodynamic flow linear dichroism of linearized DNA molecules (obtained by EcoRI enzyme digestion of covalently closed supercoiled pIBI30 DNA), modified covalently with the highly tumorigenic and mutagenic (+)-5-MeCDE derivative, indicates that flexible joints, bends, or kinks are formed at the site of binding of (+)-5-MeCDE. Slab gel data, as well as ethidium bromide-titration tube agarose gel electrophoresis data, indicate that the formation of (+)-5-MeCDE-DNA lesions causes the removal of superhelical turns with an unwinding angle of 13 +/- 3 degrees per covalently bound polycyclic aromatic residue. In contrast, the biological inactive (+)-6-MeCDE does not significantly alter the characteristics of supercoiled DNA, the unwinding angle is only 2.7 +/- 1 degrees, and the changes in persistence lengths detected by the flow linear dichroism technique are significantly smaller than in the case of (+)-5-MeCDE-DNA adducts.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗

PubMedDate not supplied

Identification of 4-(methylnitrosamino)-1-[3-(6-hydroxypyridyl)]-1-butanone as a urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in rodents.

A previously unknown urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was identified as 4-(methylnitrosamino)-1-[3-(6-hydroxypyridyl)]-1-butanone (6-hydroxyNNK). The metabolite was initially isolated from rat urine. On the basis of its MS and NMR, it was either a 4- or 6-hydroxypyridyl derivative of NNK. Model compounds were synthesized to distinguish between these possibilities; the results indicated that the metabolite was 6-hydroxyNNK. This was confirmed by independent synthesis; the spectral and chromatographic properties of 6-hydroxyNNK were the same as those of the metabolite. F-344 rats and A/J mice treated with 100 mg/kg NNK excreted approximately 1% of urinary metabolites as 6-hydroxyNNK; it was not detected as a sulfate or glucuronide conjugate. This is the first example of a pyridyl-hydroxylated metabolite of a tobacco-specific nitrosamine. On the basis of comparison to published data on other pyridine derivatives, 6-hydroxyNNK may be formed by bacterial metabolism. The potential utility of 6-hydroxyNNK as a dosimeter of human uptake of NNK is discussed.

Animals↗

PubMedDate not supplied

Synthesis of Fjord region diol epoxides as potential ultimate carcinogens of dibenzo[a,l]pyrene.

Dibenzo[a,l]pyrene (DB[a,l]P) is one of the strongest polynuclear aromatic hydrocarbon carcinogens known. This paper describes the synthesis of potential ultimate carcinogens of DB[a,l]P: anti- and syn-11,12-dihydroxy-13,14-epoxy-11,12,13,14- tetrahydroDB[a,l]P (DB-[a,l]P-11,12-diol-13,14-epoxides). The method employed is also useful for the preparation of key intermediates for the synthesis of 11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrobenzo-[g]chrysene (BgC-11,12-diol-13,14-epoxide). Photochemical cyclization of the appropriately substituted phenanthrylphenylethylenes provided 9-carbomethoxy-11-methoxyBgC (4) and 11-methoxyBgC (3). The former was converted by reduction, oxidation, one-carbon chain extension, and cyclization to 11-methoxy DB[a,l]P (7). Compounds 3 and 7 were converted by hydrolysis and oxidation to BgC-11,12-dione (10) and DB[a,l]P-11,12-dione (11), respectively. The diones are the precursors for the synthesis of the corresponding diol epoxides. anti- and syn-DB-[a,l]P-11,12-diol-13,14-epoxides 13 and 14 were prepared in 38% and 55% yields, respectively, from 11. Both diol epoxides had predominantly pseudodiequatorial hydroxyl groups, as seen in other sterically hindered diol epoxides.

Benzopyrenes↗

PubMedDate not supplied

Formation of NADP(H) analogs of tobacco-specific nitrosamines in rat liver and pancreatic microsomes.

The metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), was examined in rat pancreatic microsomes. No pyridine N-oxidation or alpha-hydroxylation were observed in these preparations. However, one unidentified metabolite of NNAL (unknown A) and two unknown metabolites of NNK (unknowns B and C) were formed. These metabolites were also detected in rat liver microsomal incubations of NNK and NNAL. Studies using [5-3H]-NNK and [Me-3H]NNK demonstrated that the metabolites contained both the pyridyl and methyl portions of the parent compound. Similar results were obtained with NNAL. Formation of unknown C required active microsomes, NADP+, and an NADPH regenerating system. The regenerating system was not required for the formation of NNAL unknown metabolite A or NNK unknown metabolite B. Chemical characterization of unknowns A and B by NMR, UV, and electrospray ionization MS demonstrated that they are NADP+ analogs in which the nicotinamide portion has been replaced by NNAL or NNK, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol adenosine dinucleotide phosphate [(NNAL)ADP+] and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone adenosine dinucleotide phosphate [(NNK)ADP+]. Unknown C was identified as (NNK)ADPH. Both (NNK)ADP+ and (NNK)ADPH were formed from NNK while only (NNAL)ADP+ was produced from NNAL. These NADP+ derivatives were also formed when porcine brain NAD+ glycohydrolase was incubated with NADP+ and NNK or NNAL. These results indicate that NNK and NNAL are substrates for rat liver and pancreatic microsomal NAD+ glycohydrolase-catalyzed transglycosylation reactions.

Adenosine Diphosphate↗

PubMedDate not supplied

Mutational spectra for 5,6-dimethylchrysene 1,2-dihydrodiol 3,4-epoxides in the supF gene of pSP189.

Dihydrodiol epoxides from 5,6-dimethylchrysene exhibit properties similar to those of fjord region-containing hydrocarbon derivatives in that they react extensively with deoxyadenosine residues in DNA and consequently generate substantial numbers of mutations at AT pairs as well as GC pairs. The syn-dihydrodiol epoxide favors reaction with deoxyadenosine (68% of adducts) to a greater extent than does the anti-dihydrodiol epoxide (52% of adducts), and point mutations at AT pairs (72% for syn- and 45% for anti-dihydrodiol epoxide) follow the same trend. A novel feature of the mutagenicity of the 5,6-dimethylchrysene derivatives is that they exhibit a higher fraction of AT-->GC transitions (28% and 26% for syn and anti, respectively) than has been seen for other hydrocarbon derivatives to date.

Base Sequence↗

PubMedDate not supplied

Identification of cis-2-butene-1,4-dial as a microsomal metabolite of furan.

The hepatocarcinogen furan is believed to be activated to the reactive aldehyde, cis-2-butene-1,4-dial, by microsomal enzymes. The rat liver microsomal metabolism of furan was examined in the presence of NADPH and semicarbazide. HPLC analysis of incubation mixtures revealed the formation of a metabolite that coeluted with standards for the bis-semicarbazone adduct of cis-2-butene-1,4-dial. The formation of this compound required the presence of NADPH, semicarbazide, and microsomes. Preparative isolation and chemical characterization of this metabolite confirmed the structural assignment. These data provide evidence that the reactive aldehyde, cis-2-butene-1,4-dial, is a major metabolic product of furan.

Aldehydes↗