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At least 91 records · Page 5Linked to original sources
PubMed1987

Toxicity of 7,12-dimethylbenz[a]anthracene and 7-hydroxymethyl-12-methylbenz[a]anthracene and its prevention in cultured rat adrenal cells. Evidence for a peroxidative mechanism of action.

The adrenocorticolytic agent DMBA and its liver metabolite, 7-OHM-12-MBA, were investigated with respect to their mechanism of toxicity in cultured rat adrenal cells. Under proper growth conditions both hydrocarbons caused a reproducible and ACTH-dependent inhibition of steroidogenesis and cell death, similar to the effects of these agents on the rat adrenal in vivo. The toxicity of both DMBA and 7-OHM-12-MBA was partially prevented by antioxidants suggesting a common peroxidative mechanism of action. Studies with cytochrome P-450 inhibitors showed that toxicity of DMBA, but not 7-OHM-12-MBA, required a cytochrome P-450-dependent metabolic activation in order to be toxic. In addition, metyrapone, an efficient and specific inhibitor of the mitochondrial 11 beta-hydroxylase, provided protection against DMBA-induced toxicity, which is in agreement with previous observations that adrenal necrosis caused by DMBA apparently originates in mitochondria. It is proposed that both 7-OHM-12-MBA and DMBA, the latter after metabolism to mainly phenols, act as pseudosubstrates for steroid hydroxylases and initiate peroxidative damage through hydroxylase-generated superoxide anion, and/or hydrogen peroxide. These results indicate that both adrenal and hepatic metabolism of DMBA are potentially important in DMBA-induced adrenocorticolysis in vivo.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Mouse skin tumor-initiating activity of 5-, 7-, and 12-methyl- and fluorine-substituted benz[a]anthracenes.

As an approach for elucidation of structure activity relationships that underlie the exceptionally large difference in carcinogenic activity between benz[a]anthracene and 7,12-dimethylbenz[a]anthracene (7,12-DMBA), 11 methyl- and/or fluorine-substituted benz[a]anthracenes were evaluated for tumor-initiating activity on mouse skin. Outbred CD-1 and outbred Sencar mice received a single topical application of the hydrocarbons followed by twice weekly applications of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate for 16-26 weeks. 7,12-DMBA was almost two orders of magnitude more active as a tumor-initiator than 7- and 12-methylbenz[a]anthracene. Methyl substitution at the 7- and 7,12-positions of benz[a]anthracene was significantly more effective in the enhancement of tumorigenic activity than fluorine substitution at these positions. Although 7-fluorobenz[a]anthracene, 12-fluorobenz[a]anthracene, and 7,12-difluorobenz[a]anthracene had only 0.15, 0.26, and less than 0.005 times the tumor-initiating activity of their respective methyl-substituted derivatives, they were severalfold more active than benz[a]anthracene. 7-Fluorobenz[a]anthracene was slightly less active than 12-fluorobenz[a]anthracene, whereas 7-methylbenz[a]anthracene was about twofold more than 12-methylbenz[a]anthracene. For 7,12-di-substituted benz[a]anthracenes, 7-methyl-12-fluorobenz[a]anthracene was more than twice as tumorigenic as 7-fluoro-12-methylbenz[a]anthracene, but each was individually more active than 7-methylbenz[a]anthracene and 12-methylbenz[a]anthracene, respectively. Both fluorinated compounds were much less active than 7,12-DMBA. Substitution of fluorine or methyl at the 5-position of 7-methylbenz[a]anthracene and substitution of fluorine at the 5-position of 12-methylbenz[a]anthracene dramatically reduced their tumorigenic activity.

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

Exceptional carcinogenic activity of benz[a]anthracene 3,4-dihydrodiol in the newborn mouse and the bay region theory.

Benz[a]anthracene and the five metabolically possible trans-dihydrodiols of benz[a]anthracene were tested for carcinogenicity in newborn Swiss-Webster mice. Four hundred, 800, and 1600 nmoles hydrocarbon i.p. were sequentially injected on Days 1, 8, and 15 of life. The mice were killed at 22 weeks of age. Of the mice treated with trans-3,4-dihydroxy-3, 4-dihydrobenz[a]anthracene, 24% developed malignant lymphoma, whereas 4% of the animals treated with benz[a]anthracene had malignant lymphoma. None of the animals treated with the trans-1,2-dihydroxy-1,2-dihydrobenz[a]anthracene, trans-5,6-dihydroxy-5,6-dihydrobenz[a]anthracene, trans-8,9-dihydroxy-8,9-dihydrobenz[a]anthracene, or trans-10,11-dihydroxy-10,11-dihydrobenz[a]anthracene had malignant lymphoma. trans-3,4-Dihydroxy-3,4-dihydrobenz[a]anthracene caused about 35-fold more pulmonary adenomas than did benz[a]anthracene, whereas the trans-1,2-dihydroxy-1,2-dihydrobenz[a]anthracene, trans-5,6-dihydroxy-5,6-dihydrobenz[a]anthracene, trans-8,9-dihydroxy-8,9-dihydrobenz[a]anthracene, and trans-10, 11-dihydroxy-10,11-dihydrobenz[a]anthracene had little or no activity. The exceptionally high carcinogenicity of trans-3,4-dihydroxy-3,4-dihydrobenz[a]anthracene is consistent with the metabolism of this compound to either or both of the diastereomeric bay region 3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenz[a]anthracenes, and the data support the bay region theory of polycyclic hydrocarbon carcinogenesis.

Adenoma↗
PubMed2005

Degradation of benz[a]anthracene by Mycobacterium vanbaalenii strain PYR-1.

Cultures of Mycobacterium vanbaalenii strain PYR-1 grown in mineral salts medium and nutrients in the presence of benz[a]anthracene metabolized 15% of the added benz[a]anthracene after 12 days of incubation. Neutral and acidic ethyl acetate extractable metabolites were isolated and characterized by high performance liquid chromatography (HPLC) and uv-visible absorption, gas chromatography/mass (GC/MS) and nuclear magnetic resonance (NMR) spectral analysis. Trimethylsilylation of the metabolites followed by GC/MS analysis facilitated identification of metabolites. The characterization of metabolites indicated that M. vanbaalenii initiated attack of benz[a]anthracene at the C-1,2-, C-5,6-, C-7,12- and C-10,11-positions to form dihydroxylated and methoxylated intermediates. The major site of enzymatic attack was in the C-10, C-11 positions. Subsequent ortho- and meta-cleavage of each of the aromatic rings led to the accumulation of novel ring-fission metabolites in the medium. The major metabolites identified were 3-hydrobenzo[f]isobenzofuran-1-one (3.2%), 6-hydrofuran[3,4-g]chromene-2,8-dione (1.3%), benzo[g]chromene-2-one (1.7%), naphtho[2,1-g]chromen-10-one (48.1%), 10-hydroxy-11-methoxybenz[a]anthracene (9.3%), and 10,11-dimethoxybenz[a]anthracene (36.4%). Enzymatic attack at the C-7 and C-12 positions resulted in the formation of benz[a]anthracene-7,12-dione, 1-(2-hydroxybenzoyl)-2-naphthoic acid, and 1-benzoyl-2-naphthoic acid. A phenyl-naphthyl metabolite, 3-(2-carboxylphenyl)-2-naphthoic acid, was formed when M. vanbaalenii was incubated with benz[a]anthracene cis-5,6-dihydrodiol, indicating ortho-cleavage of 5,6-dihydroxybenz[a]anthracene. A minor amount of 5,6-dimethoxybenz[a]anthracene was also formed. The data extend and propose novel pathways for the bacterial metabolism of benz[a]anthracene.

Benz(a)Anthracenes↗
PubMed1972

Epoxy derivatives of aromatic polycyclic hydrocarbons. The synthesis of dibenz[a,c]anthracene 10,11-oxide and its metabolism by rat liver preparations.

The synthesis of dibenz[a,c]anthracene 10,11-oxide is described. The oxide was unstable and was rapidly decomposed with cold mineral acid into a mixture of 10- and 11- hydroxydibenz[a,c]anthracene. The oxide was converted by rat liver microsomal preparations and homogenates into a product that is probably 10,11-dihydro-10,11-dihydroxydibenz[a,c]anthracene and which was identical with the metabolite formed when dibenz[a,c]anthracene was metabolized by rat liver homogenates. The oxide did not react either chemically or enzymically with GSH. 10,11-Dihydrodibenz[a,c]anthracene and 10,11-dihydrodibenz[a,c]anthracene 12,13-oxide were both metabolized by rat liver preparations into trans-10,11,12,13-tetrahydro-10,11-dihydroxydibenz[a,c] anthracene and the oxide was converted chemically into this dihydroxy compound, and it reacted chemically but not enzymically with GSH. In the alkylation of 4-(p-nitrobenzyl)pyridine, the ;K-region' epoxide, dibenz[a,h]anthracene 5,6-oxide, was more active than either dibenz[a,c]anthracene 10,11-oxide or 10,11-dihydrobenz[a,c]anthracene 12,13-oxide.

Alkylation↗