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At least 19 recordsLinked to original sources
PubMed1978

The formation of dihydrodiols by the chemical or enzymic oxidation of benz[a] anthracene and 7,12-dimethylbenz[a] anthracene.

When benz[a] anthracene was oxidised in a reaction mixture containing ascorbic acid, ferrous sulphate and EDTA, the non-K-region dihydrodiols, trans-1,2-dihydro-1,2-dihydroxybenz[a] anthracene and trans-3,4-dihydro-3,4-dihydroxybenz[a] anthracene together with small amounts of the 8,9- and 10,11-dihydrodiols were formed. When oxidised in a similar system, 7,12-dimethylbenz[a] anthracene yielded the K-region dihydrodiol, trans-5,6-dihydro-5,6-dihydroxy-7,12-dimethylbenz[a] anthracene and the non-K-region dihydrodiols, trans-3,4-dihydro-3,4-dihydroxy-7,12-dimethylbenz[a] anthracene, trans-8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz[a] anthracene, trans-10,11-dihydro-10,11-dihydroxy-7,12-dimethylbenz[a] anthracene and a trace of the 1,2-dihydrodiol. The structures and sterochemistry of the dihydrodiols were established by comparisons of their UV spectra and chromatographic characteristics using HPLC with those of authentic compounds or, when no authentic compounds were available, by UV, NMR and mass spectral analysis. An examination by HPLC of the dihydrodiols formed in the metabolism, by rat-liver microsomal fractions, of benz[a] anthracene and 7,12-dimethylbenz[a] anthracene was carried out. The metabolic dihydriols were identified by comparisons of their chromatographic and UV or fluorescence spectral characteristics with compounds of known structures. The principle metabolic dihydriols formed from both benz[a] anthracene and 7,12-dimethylbenz[a] anthracene were the trans-5,6- and trans-8,9-dihydrodiols. The 1,2- and 10,11-dihydrodiols were identified as minor products of the metabolism of benz [a] anthracene and the tentative identification of the trans-3,4-dihydriol as a metabolite was made from fluorescence and chromatographic data. The minor metabolic dihydriols formed from 7,12-dimethylbenz[a] anthracene were the trans-3,4-dihydrodiol and the trans-10,11-dihydriol but the trans-1,2-dihydrodiol was not detected in the present study.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1977

Tumorigenicity of five dihydrodiols of benz(a)anthracene on mouse skin: exceptional activity of benz(a)anthracene 3,4-dihydrodiol.

Benz[a]anthracene and the five metabolically possible vicinal trans dihydrodiols of benz[a]anthracene were tested for ability to initiate skin tumors in CD-1 female mice. A single topical application of 0.4-2.0 mumol of hydrocarbon was followed 18 days later by twice weekly applications of the skin promoter 12-O-tetradecanoylphorbol-13-acetate. Comparisons of latency period, percent of mice with tumors, and number of papillomas observed per mouse indicated that benz[a]anthracene 1,2-, 5,6-, 8,9-, and 10, 11-dihydrodiols were all less active tumor initiators than was benz[a]anthracene. The high tumorigenicity of benz[a]anthracene 3,4-dihydrodiol, presumably the result of metabolism to either or both of the diastereomeric benz[a]anthracene 3,4-diol-1,2-epoxides, supports the bay region theory of polycyclic hydrocarbon carcinogenicity and provides the first example of a proximate carcinogenic metabolite that is much more active than the parent hydrocarbon on mouse skin.

Animals↗
PubMed1975

Glutathione conjugates as metabolites of benz[a]anthracene.

1. [3H]Benz[a]anthracene is converted into water-soluble metabolites by microsomal plus soluble fractions of rat-liver in the presence of NADPH and glutathione. Chromatography on Sephadex G25 gave four radioactive peaks; the first contained hydrocarbon or hydrocarbon derivatives bound to soluble protein while the other three peaks contained glutathione conjugates of hydrocarbon metabolites. 2. Conjugates formed when either of the benz[a]anthracene metabolites, 5,6-dihydro-5,6-dihydroxybenz[a]anthracene or 8,9-dihydro-8,9-dihydroxybenz[a]anthracene, were similarly incubated were probably S-(5,6,8,9-tetrahydro-5,6,9-trihydroxybenz[a]anthracen-8-yl)glutathione and S-(5,6,8,9-tetrahydro-6,8,9-trihydroxybena[a]anthracen-5-yl)glutathione respectively. The corresponding peak obtained in the metabolism of benz[a]anthracene probably contains a mixture of these two isomers. 3. The third peak contained the conjugate, S-(5,6-dihydro-l-hydroxybenz-[a]anthracen-k-yl)glutathione, also formed by the conjugation of the "K-region" epoxide of benz[a]anthracene with glutathione. This was not formed in the metabolism of the dihydrodiols. 4. The fourth peak contained a new type of conjugate that is probably S-(8,9,10,11-tetrahydro-8,9,10-trihydroxybenz[a]anthracen-11-yl)glutathione. This conjugate is chromatographically similar to a product obtained from incubation of the 8,9-dihydrodiol, and is probably formed by microsomal oxidation of the 10,11-bond of the dihydrodiol, followed by conjugation of the resulting diol-epoxide with glutathione.

Animals↗
PubMed1979

Tumorigenicity of the diastereomeric benz[a]anthracene 3,4-diol-1,2-epoxides and the (+)- and (-)-enantiomers of benz[a]anthracene 3,4-dihydrodiol in newborn mice.

The tumorigenic activity of benz[a]anthracene (BA), the (+)- and (-)-enantiomers of trans-3,4-dihydroxy-3,4-dihydrobenz[a]anthracene (BA 3,4-dihydrodiol), and the racemic diastereomers of the BA 3,4-diol-1,2-epoxides [i.e., either or both of the diastereomeric 1,2-epoxides derived from BA 3,4-dihydrodiol in which the epoxide oxygen is cis (diol epoxide-1) or trans (diol epoxide-2) to the benzylic 4-hydroxyl group) was examined in newborn Swiss-Webster mice. The mice were administered ip a total dose of 280 nmoles of compound in divided doses consisting of 40 nmoles within 24 hours of birth, 80 nmoles at 8 days of age, and 160 nmoles at 15 days of age. The experiment was terminated when the animals were 26 weeks of age. BA 3,4-diol-1,2-epoxide-2 was the most potent compound tested. All animals treated with BA 3,4-diol-1,2-epoxide-2 developed pulmonary tumors with an average of 13.3 tumors per mouse. BA 3,4-diol-1,2-epoxide-1 produced pulmonary tumors in 42% of the mice with an average of only 0.56 tumors per mouse. The (-)-enantiomer of BA 3,4-dihydrodiol with [3R,4R] absolute stereochemistry was the second most tumorigenic derivative of BA tested; it produced pulmonary tumors in 71% of the mice with an average of 1.88 tumors per mouse. BA and the (+)-enantiomer of BA 3,4-dihydrodiol had little or no tumorigenic activity at the dose tested. A comparison of the average number of pulmonary tumors per mouse revealed that BA 3,4-diol-1,2-epoxide-2 was about 30-fold more tumorigenic than was BA 3,4-diol-1,2-epoxide-1, 8-fold more tumorigenic than was (-)-BA 3,4-dihydrodiol, and greater than 85-fold more tumorigenic than was BA. These data indicate that in newborn mice BA 3,4-dihydrodiol and a BA 3,4-diol-1,2-epoxide are proximate and ultimate carcinogenic metabolites of BA, respectively.

Animals↗
PubMed1979

Comparison of mutagenesis and malignant transformation by dihydrodiols from benz[a]anthracene and 7,12-dimethylbenz[a]anthracene.

Five dihydrodiols derived from benz[a]anthracene (BA) and 4 dihydrodiols derived from 7,12-dimethylbenz[a]anthracene (DMBA) have been tested, together with the parent hydrocarbons, for their abilities to induce mutations to 8-azaguanine resistance in V79 (Chinese hamster cells and malignant transformation in M2 mouse fibroblasts. The syn- and anti-isomers of benz[a]anthracene 8,9-diol 10,11-oxide were also tested for biological activity in these two systems. The non-K-region 1,2- and 3,4-dihydrodiols of BA induced mutations but the non-K-region 8,9-dihydrodiol and the K-region 5,6-dihydrodiol were inactive as mutagens; none of these BA diols transformed M2 mouse fibroblasts. The 3,4- and the 8,9-dihydrodiols derived from 7,12-dimethylbenz[a]anthracene induced mutations in V79 cells and malignant transformation in M2 mouse fibroblasts and both were more active than the hydrocarbon itself. The K-region 5,6-dihydrodiol and the non-K-region 10,11-dihydrodiol of DMBA were inactive in both test systems. The results are not inconsistent with other data suggesting that the metabolic activation of both BA and DMBA occurs through conversion of the respective 3,4-dihydrodiols into the related vicinal diol-epoxides, although other dihydrodiols may also be involved in vivo. Both the BA diol-epoxides tested were mutagenic, but although the anti-isomer transformed M2 fibroblasts, the syn-isomer was inactive.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Pathologic changes induced in respiratory tract mucosa by polycyclic hydrocarbons of differing carcinogenic activity.

Seven aromatic polycyclic hydrocarbons (PCHs) were investigated for their toxic effects on respiratory mucosa: benzo(e)pyrene (BeP), pyrene, anthracene, benz(a)anthracene(BaA), dibenz(a,c)anthracene(DBacA), benzo (a)pyrene (BaP), and dimethylbenz(a)anthracene (DMBA). The compounds were chosen because they comprise a spectrum of PCHs ranging from noncarcinogens, to initiators, to weak and strong carcinogens. All of them except DMBA are environmentally relevant chemicals. The chemicals were tested over an 8-week period. Heterotopic tracheal transplants were continously exposed and the histopathologic effects induced by the various PCHs were periodically assessed semiquantitatively. All PCHs exhibited varying degrees of toxicity for respiratory epithelium and submucosa. BeP clearly showed the least toxicity followed by pyrene and anthracene. BaA and DBacA caused marked epithelial and submucosal changes. In addition to epithelial hyperplasia, undifferentiated epithelium and squamous metaplasia developed. Marked mononuclear infiltration occurred in the subepithelial connective tissue. With BaP the epithelial and submucosal changes were similar but were much stronger. DMBA was the most toxic substance, causing epithelial necrosis followed by generalized keratinizing squamous metaplasia; the subepithelial changes consisted of an early acellular exudate and, later (at 8 weeks), marked condensation and hyalinization of the lamina propria. The toxic response pattern of the tracheal mucosa to carcinogenic agents was characterized by the chronicity of epithelial and connective tissue damage, as opposed to the short-lived hyperplastic and inflammatory response elicited by the noncarcinogens and weak initiators.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1977

Mutagenicity and cytotoxicity of benz[alpha]anthracene diol epoxides and tetrahydro-epoxides: exceptional activity of the bay region 1,2-epoxides.

Three diastereomeric pairs of diol epoxides, two tetrahydro-epoxides, and the K-region oxide of the polycyclic aromatic hydrocarbon benz[a]anthracene were evaluated for mutagenic activity in strain TA 100 of Salmonella typhimurium and in line V79-6 of Chinese hamster lung cells. The two diastereomeric 1,2-epoxides of the trans-3,4-dihydrodiol of benz[a]anthracene are 15 to 35 times more mutagenic to the bacteria and 65 to 125 times more mutagenic to the mammalian cells than are the diastereomeric pairs of benz[a]anthracene-8,9-diol-10,11-epoxides or benz[a]anthracene-10,11-diol-8,9-epoxides. 1,2-Epoxy-1,2,3,4-tetrahydrobenz[a]anthracene is the most mutagenic and cytotoxic of the nine derivatives and is 5 and 25 times more mutagenic than 3,4-epoxy-1,2,3,4-tetrahydrobenz[a]anthracene in bacterial and mammalian cells, respectively. In either test system, benz[a]anthracene 5,6-oxide (K-region oxide) has less than 10% of the activity of any of the 1,2-epoxides derived from benz[a]anthracene. The relative stabilities of the derivatives in aqueous solution do not account for the differences in mutagenic activity because the more mutagenic derivatives tend to be less stable. The benz[a]anthracene diol epoxides, like the benzo[a]pyrene diol epoxides, are refractory to the action of epoxide hydrase. The exceptional mutagenic activity of the 1,2-epoxide derivatives of benz[a]anthracene is consistent with and supportive of the hypothesis that bay region epoxides on saturated, angular benzo-rings of unsubstituted polycyclic aromatic hydrocarbons are ultimate carcinogens.

Benz(a)Anthracenes↗
PubMed1977

Mutagenicity of isomeric diol-epoxides of benzo[a]pyrene and benz[a]anthracene in S. typhimurium TA98 and TA100 and in V79 Chinese hamster cells.

Pairs of isomeric vicinal diol-epoxides derived from benzo[a]pyrene 7,8- and 9,10-dihydrodiols and from benz[a]anthracene 8,9-dihydrodiol were tested for their abilities to revert salmonella typhimurium strains TA98 and TA100 to histidine prototrophy and to induce the formation of 8-azaguanine- or of ouabain-resistant V79 Chinese hamster cells. All six diol-epoxides were active in both bacterial strains, but 7beta,8alpha-dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (the syn isomer) was considerably more mutagenic than the other diol-epoxides. Within the three pairs of stereo-isomeric diol-epoxides, the ratio of the mutagenic potencies of the syn over the related anti isomers varied bothwith the chemical structure and the bacterial strain. The half lives of hydration of these diol-epoxides at pH 7.4 were inversely related to their mutagenic potencies in bacteria. In V79 cells, the two benzo[a]pyrene 7,8-diol 9,10-oxides were mutagenic and the anti isomer was more active than the syn isomer; a reversed order of mutagenic potency with these stereo isomers was observed in S. typhimurium. The other four diol-epoxides were non-mutagenic in V79 cells at the concentrations tested.

Benz(a)Anthracenes↗
PubMed1977

[Effect of DMBA and benz (alpha) anthracene on the biogenic amine level in the rat brain].

Thirty minutes after the administration of DMBA (5 mg i. v.) to rats the level of norepinephrine, dopamine, serotonine (5-HT) and 5-IIIAA in the hypothalamus was decreased, while monoamines levels in the brain stem and hemispheres was unchanged. After benz(a) anthracene (5 mg i.v.) treatment the level of 5-HT in rat hypothalamus was decreased, but catecholamines and 5-HIAA levels were not changed. Pretreatment with L-DOPA abolished the elevation of the threshold of hypothalamic sensitivity to estrogen suppression, induced by 20-methylcholanthrene in rats, and alpha-methyl-DOPA enhanced. It is suggested that the central (hypothalamic) mechanisms participate in the release of the carcinogenic effect of polycylic hydrocarbons in rats.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Shapes of carcinogenic benz[a]anthracenes: the crystal and molecular structure of 1-methylbenz[a]anthracene.

The crystal structure of 1-methylbenz[a]lanthracene, which is weakly carcinogenic, has been determined by application of direct methods to single-crystal X-ray diffractometric data and refined by least squares to R = 0.09 over 845 independent reflections. Crystals are monoclinic, space group P2(1), with a = 8.491(2), b = 7.138(2), c = 10.500(2)ABEta = 95.06(01), Z = 2. As in other benz[a]anthracenes, the K-region bond C(5)-C(6) is short [1.34(1)A]. The distinctive bay geometry, with a methyl group opposite to a hydrogen, H(12), peri to another hydrogen, H(11), has a long bond C(13)--C(18) = 1.47(1)A in the bay, and the angular benz-ring is inclined at 16.5 degrees to the mean plane of the anthracene fragment. The methyl carbon atom is 0.79 A out of the mean molecular plane (or 0.19 A out of the plane of the benz-ring) and the 1.50 A long C(1)-methyl bond makes angles of 117 degrees and 125 degrees at C(1).

Benz(a)Anthracenes↗
PubMed1979

DNA binding and mutagenicity of 7-substituted derivatives of benz[A]anthracene.

The binding of carcinogenic 7-hydroxymethylbenz[a]anthracene (7-HOCH2-B[a]A) and 7-acetoxymethylbenz[a]anthracene (7-AcOCH2-B[a]A) to calf thymus DNA was studied in the presence or absence of microsomal enzymes or nucleoside phosphates. In the absence of microsomes or ATP little or no binding was detected for either hydrocarbon (HC). Microsomal enzymes significantly enhanced the binding of both HC's to DNA when compared to control as measured by radioactivity bound to DNA. When 7-HOCH2-B[a]A was incubated at 37 degrees with ATP there was a linear increase in binding over a six hr period. Of the nucleoside phosphates tested, ATP, and to a lesser extent ADP and CTP, mediated binding of 7-HOCH2-B[a]A suggesting formation of a reactive phosphate ester. Mutagenicity studies with 7-acetoxymethyl, 7-hydroxymethyl, 7-formyl-, 7-methyl-, and 7-methoxymethyl-B[a]A were conducted using the Salmonella reverse mutation assay. All compounds exhibited mutagenic activity in the presence of S-9; only 7-AcOCH2-B[a]A was active without S-9 indicating this compound to be an ultimate mutagen.

Animals↗
PubMed1979

Characteristics of aryl hydrocarbon hydroxylase activity in rat mammary epithlial cells grown in primary culture.

Rat mammary epithelial cells grown in primary culture contain the microsomal enzyme, aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH), which catalyses the oxidative conversion of polycyclic aromatic hydrocarbons (PAH) to more polar derivatives. Constitutive AHH activity, measured with an established fluorometric method, was 46 pmol/mg protein/h in homogenates of rat mammary epithelial cells after 5 days in culture. The addition of dimethylbenz[a]anthracene (DMBA), benz[a]anthracene (BA), or 3-methylcholanthrene (3-MC) to the cell culture medium increased AHH activity 5.3-, 4.7- and 2.4-fold, respectively. Kinetic studies revealed that maximal hydroxylase induction occurred 16 h after 1 micro M DMBA was added to the culture medium. The decay of the DMBA-induced hydroxylase was biphasic: one component had a t1/2 of 15--30 min and another a t1/2 of 4 h. Norepinephrine, 17 beta-estradiol and 5,6-benzoflavone also increased AHH activity in mammary epithelial cells in vitro, however, sodium phenobarbital had no effect. Fetal bovine serum (FBS), previously shown to be a potent in vitro inducer of AHH activity, had no effect on either constitutive or DMBA-induced mammary epithelial hydroxylase activities following treatment with 1% activated charcoal. Metyrapone and 7,8-benzoflavone, inhibitors of microsomal mixed function oxidase activity, reduced both constitutive and DMBA-induced AHH activities when added to homogenates of untreated and DMBA-treated mammary epithelial cells. The addition of 7,8-benzoflavone reduced both constitutive and DMBA-induced hydroxylase activities by approx. 80%, whereas metyrapone addition inhibited these activities by 20%. The study demonstrates several in vitro factors which alter AHH activity in primary cultures of rat mammary epithelial cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

DNA-protein cross-linking by chemical carcinogens in mammalian cells.

The induction of DNA cross-linking in mammalian cells by various carcinogens was investigated by the method of alkaline elution. A dose-dependent increase in DNA cross-linking was seen following exposure of human fibroblasts to N-acetyoxy-2-acetylaminofluorene and following exposure of mouse embryo cells to 7,12-dimethylbenz[a]-anthracene. No cross-link effect was seen following treatment with N-methyl-N'-nitro-N-nitrosoguanidine, benz-[a]anthracene, benz[A]anthracene-5,6-dihydroepoxide, or metabolic inhibitors. The cross-linking appeared to be DNA-protein in nature since proteinase treatment removed the effect. DNA single-strand breaks were also induced by several of these agents in the case of N-acetoxy-2-acetylaminofluorene and N-methyl-N'-nitro-N-nitrosoguanidine, approximately 70 to 90% of these breaks were rejoined after an 18-hr incubation in fresh medium, whereas repair of the cross-links induced by N-acetoxy-2-acetylaminofluorene was slight at this time.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Independent regulation of two types of aryl hydrocarbon (benzo(a)pyrene) hydroxylase in mammalian cells.

Aryl hydrocarbon (benzo(a)pyrene) hydroxylase induced by dibutyryl cyclic AMP (dcAMP), plus aminophylline (AHH I) can be ditsinguished from the hydroxylase induced by benz (a) anthracene (AHH II) by its lower Km for benzo (a) pyrene. Treatment with the combination of benzo (a) anthracene and dcAMP plus aminophylline induced both AHH I and AHH II activities. After optimal induction of AHH II activity by benz (a) anthracene, the addition of dcAMP plus aminophylline gave an induction of AHH I. Although AHH I activity declined to an almost basal level 24 h after treatment with dcAMP plus aminophylline, the addition of benz (a) anthracene prevented this decline. Inducibility by dcAMP plus aminophylline or by benz (a) anthracene varied in different cell lines. Some cell lines were induced by both substances, with a higher induction by benz (a) anthracene, while other lines were inducible only by benz (a) anthracene, and a third cell type was not inducible by either. Selection for resistance to benzo (a) pyrene of a cell line inducible by both compounds resulted in a fourth cell type which was more inducible by dcAMP plus aminophylline than by benz (a) anthracene. The results suggest that there is an independent regulation of hydroxylase AHH I and AHH II and that the induction of these two enzyme activities is determined by different genetic controls.

Aminophylline↗