RESUMEN
The relative mutagenic potentials of 11-amino-16,17-dihydro-15H-cyclopenta[a]phenanthrene, its 17-keto derivative, and 2- and 5-aminochrysene have been compared in Salmonella typhimurium TA98 and TA100 in the presence of a postmitochondrial liver preparation from Aroclor 1254 induced rats. The 11-amino hydrocarbon is a very weak mutagen (0.27 revertants/nmol), whereas the 11-amino-17-ketone is much more active (129 revertants/nmol). 2-Aminochrysene is the most mutagenic arylamine ( approximately 500 revertants/nmol) among these compounds, but its 5-amino isomer is much less active (0.9 revertants/nmol). Possible reasons for these marked differences are suggested. Use of TA98 with over-expressing O-acetyltransferase (YG 1024) and deficient in this enzyme (TA98/l,8-DNP(6)) with the 11-amino-17-ketone and with 5-aminochrysene clearly indicates the importance of this enzyme in their bioactivation, implying oxidation of the amino group to the hydroxylamine in both these compounds.
Asunto(s)
Androstenos/toxicidad , Crisenos/toxicidad , Mutágenos/toxicidad , Animales , Región Bahía de Hidrocarburos Aromáticos Policíclicos , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Pruebas de Mutagenicidad , Ratas , Ratas Wistar , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genética , Relación Estructura-ActividadRESUMEN
Whole homogenates of Agaricus bisporus metabolised the mushroom hydrazine agaritine [beta-N-(gamma-L(+)glutamyl)-4-(hydroxymethyl) phenylhydrazine] to generate at least three metabolites. None of these metabolites, however, was the free hydrazine [4-(hydroxymethyl)phenylhydrazine], the postulated metabolite of agaritine believed to be formed as a result of the loss of the gamma-glutamyl group, the reaction being catalysed by gamma-glutamyltransferase. The three metabolites of agaritine displayed weak mutagenic activity towards Salmonella typhimurium strain TA104. 4-(Hydroxymethyl)phenylhydrazine, as the N'-acetyl derivative, was metabolised by mushroom tyrosinase to yield a number of metabolites that induced a mutagenic response in S. typhimurium TA104. Similar to N'-acetyl-4-(hydroxymethyl)phenylhydrazine, agaritine was extensively metabolised by the mushroom tyrosinase but, in contrast, the structurally related N'-acetyl-4-hydrazinobenzoic acid did not serve as substrate of this enzyme, implying a critical role for the hydroxymethyl group at the para-position. In conclusion, the current studies have demonstrated for the first time that: (a) whole mushroom homogenates readily metabolise agaritine but not to the postulated 4-(hydroxymethyl)phenylhydrazine; and (b) mushroom tyrosinase metabolises agaritine and N'-acetyl-4-(hydroxymethyl)phenylhydrazine, in the latter case forming genotoxic metabolites.
Asunto(s)
Agaricales/metabolismo , Hidrazinas/farmacocinética , Monofenol Monooxigenasa/metabolismo , Fenilhidrazinas/farmacocinética , Agaricales/química , Agaricales/enzimología , Biotransformación , Hidrazinas/metabolismo , Hidrazinas/toxicidad , Monofenol Monooxigenasa/aislamiento & purificación , Monofenol Monooxigenasa/farmacología , Pruebas de Mutagenicidad , Mutágenos/metabolismo , Mutágenos/farmacocinética , Mutágenos/toxicidad , Fenilhidrazinas/metabolismo , Fenilhidrazinas/toxicidadRESUMEN
Using 500 MHz NMR, we have carried out a stable ion protonation and model nitration study of the methoxy-substituted hydrocarbon 6, its 15-ol 7, and the dimer 10, in order to evaluate OMe substituent effects on directing electrophilic attack and on charge delocalization mode/conformational aspects in the resulting carbocations. It is found that the C-11 methoxy group directs the electrophilic attack to C-12 and C-14. Thus protonation of 6 with FSO(3)H/SO(2)ClF gives a 4:1 mixture of monoarenium ions 6H(+)()/6aH(+)(). Prolonged reaction times and increased temperature induced fluorosulfonylation at C-14 (6(+)-SO(2)()F), whereas ambient nitration with NO(2)(+)BF(4)(-) occurred at C-12. The 15-ol derivative 7 is cleanly ionized to 11(+)(), providing the first example of an alpha-phenanthrene-substituted carbocation from phenanthrene C-1 position. Contrasting behavior of the D-ring methyl-substituted 9 and the C-11 methoxy-substituted 10 dimers is remarkable in that unlike 9 which is readily cleaved to produce the monomeric arenium ion 3H(+)(), 10 is diprotonated at the two C-12 sites and at C-12/C-14 in each unit. The latter dication-dimer exists as a mixture of diastereomers. Reactivity of 7 underscores the importance of 11(+)(). Attack at the C-14 ring junction is in concert with the proposal that electrophilic oxygen would attack at C-14/C-15 (epoxidation) followed by ring opening to give the biologically active 15-ol as a major metabolite.
Asunto(s)
Fenantrenos/síntesis química , Cationes , Indicadores y Reactivos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Fenantrenos/química , Solventes , Relación Estructura-ActividadRESUMEN
The fate of the mushroom hydrazine [14C]agaritine was investigated in the mouse and rat strains previously employed in carcinogenicity studies with the edible mushroom Agaricus bisporus. Agaritine was rapidly absorbed in both species, achieving higher blood levels in the mouse, but with similar area under the curve. Covalent binding of agaritine material to proteins was detected only in the liver and kidney, but the extent of binding was the same in the rat and mouse. Most of the radioactivity was excreted during the first 24 hours in both animal species: in the rat it was distributed equally between urine and feces, whereas in the mouse more of the radioactivity was excreted in the urine. No qualitative differences in the metabolic profile were evident, but quantitative differences were observed. Treatment of the urine with deconjugating enzymes did not reveal the presence of any conjugates. Agaritine, N'-acetyl-4-(hydroxymethyl)phenylhydrazine, and 4-(hydroxymethyl)benzene diazonium ion were not detected in the urine or in the plasma of either species. No mutagens or promutagens were detected by the Ames mutagenicity assay in the urine of either species after exposure to agaritine. Repeated administration of agaritine to rats and mice did not alter the urinary metabolic profile and excretion of radioactivity. Similarly, feeding mice a raw mushroom diet, according to the protocol employed in the carcinogenicity studies, did not modulate the excretion of radioactivity or the urinary metabolic pattern. No major species differences in the fate of agaritine in rat and mouse were noted that could provide a rationale for the carcinogenicity of A. bisporus in the mouse, but not in the rat.
Asunto(s)
Agaricus , Riñón/metabolismo , Hígado/metabolismo , Fenilhidrazinas/farmacocinética , Animales , Área Bajo la Curva , Heces/química , Tasa de Depuración Metabólica , Ratones , Modelos Animales , Pruebas de Mutagenicidad , Fenilhidrazinas/sangre , Fenilhidrazinas/orina , Unión Proteica , Ratas , Factores de TiempoRESUMEN
The title compound is a more potent carcinogen than would be anticipated from its simple phenanthrene structure lacking further D-ring conjugation. In vitro it undergoes microsomal metabolism to yield as major metabolites its 15- and 17-alcohols and its 16, 17-diol; other minor metabolites are also derived from attack at the 5-membered ring, but no evidence of aromatic oxidation is apparent. The title compound is a weak mutagen in the Ames' test with Salmonella typhimurium TA100, but only with microsomal bio-activation. The 17-ol and 16,17-diol are inactive, with or without biological activation. By contrast the 15-alcohol, a rather reactive compound, is a strong mutagen both in the presence and absence of the bio-activation system. This, therefore, may be the proximate carcinogen, and its structural analogy to the naturally occurring hepato-carcinogen safrole is noted.
Asunto(s)
Androstenos/farmacocinética , Androstenos/toxicidad , Carcinógenos/farmacocinética , Carcinógenos/toxicidad , Androstenos/química , Animales , Biotransformación , Carcinógenos/química , Técnicas In Vitro , Masculino , Microsomas Hepáticos/metabolismo , Pruebas de Mutagenicidad , Ratas , Ratas Wistar , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genética , Relación Estructura-ActividadRESUMEN
Agaritine (N2-[L-(+)-glutamyl]-4-(hydroxymethylphenyl)hydrazine), the principal hydrazine found in the edible mushroom Agaricus bisporus, as well as the N'-acetyl derivative of 4-(hydroxymethyl)phenylhydrazine and 4-(hydroxymethyl)benzene diazonium ion, as the tetraborate salt, considered as the putative proximate and ultimate carcinogens of agaritine, were all synthesised chemically. The mutagenicity of these compounds and of 4-hydrazinobenzoic acid, a precursor of agaritine biosynthesis in mushroom, was investigated in the Ames test, using Salmonella typhimurium strain TA104, in the absence and in the presence of either mushroom tyrosinase or rat hepatic cytosol as activation systems. In the absence of an activation system the diazonium ion was clearly the most mutagenic of the four compounds studied. When tyrosinase was used as activation system, the mutagenicity of N'-acetyl-4-(hydroxymethyl)phenylhydrazine was enhanced; glutathione and superoxide dismutase markedly suppressed the mutagenic response. When the mutagenicity of the four compounds was evaluated in the presence of rat hepatic cytosol, an increase was seen only in the case of N'-acetyl-4-(hydroxymethyl)phenylhydrazine; this was shown to be due to deacetylation releasing the more mutagenic free hydrazine. Collectively, the above data are compatible with an activation of agaritine that involves an initial loss of the gamma-glutamyl group followed by microsomal oxidation of the free hydrazine to generate the diazonium ion. Also of interest is the observation that mushroom tyrosinase can convert N'-acetyl-4-(hydroxymethyl)phenylhydrazine to mutagenic product(s); whether these products contribute to the mutagenicity of mushroom extracts remains to be established.
Asunto(s)
Agaricus/química , Benzoatos , Hidrazinas/metabolismo , Hidrazinas/toxicidad , Mutágenos/toxicidad , Animales , Arocloros/farmacología , Benzoatos/metabolismo , Benzoatos/farmacología , Biotransformación , Citosol/metabolismo , Relación Dosis-Respuesta a Droga , Hígado/metabolismo , Masculino , Microsomas Hepáticos/metabolismo , Monofenol Monooxigenasa/metabolismo , Pruebas de Mutagenicidad , Mutágenos/metabolismo , Fenilhidrazinas/metabolismo , Fenilhidrazinas/farmacología , Fenilhidrazinas/toxicidad , Ratas , Ratas Sprague-Dawley , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genéticaRESUMEN
The present study was undertaken to establish whether liver and kidney enzyme systems, from rat and mouse, have the potential to metabolise and bioactivate agaritine, beta-N-(gamma-L(+)glutamyl)-4-(hydroxymethyl)phenylhydrazine, the most abundant hydrazine present in the edible mushroom Agaricus bisporus. Agaritine was weakly mutagenic, in the absence of an activation system, in Salmonella typhimurium strain TA104. Rat kidney homogenates, characterised by high gamma-glutamyl transpeptidase activity, enhanced the mutagenic response. In contrast, hepatic microsomes, having very low gamma-glutamyl transpeptidase activity, did not influence the mutagenicity of agaritine. However, hepatic microsomes could further potentiate the mutagenic response induced by the kidney. Agaritine was a good substrate for purified gamma-glutamyl transpeptidase, being converted to a major metabolite, 4-(hydroxymethyl)phenylhydrazine, formed as a result of the loss of the glutamyl moiety. Kidney homogenates from the rat and mouse also catalysed this reaction, the former being the more effective. Metabolism of agaritine was suppressed by serine-borate, an inhibitor of gamma-glutamyl transpeptidase. Kidney homogenates from rat and mouse could metabolise agaritine to intermediate(s) that bound covalently to proteins, with the rat preparations being the more effective; covalent binding was inhibited by glutathione. In contrast, hepatic preparations alone were ineffective in producing such covalent binding but did further increase the covalent binding mediated by the kidney preparations. It is concluded that rat and mouse kidney homogenates catalyse the removal of the glutamyl group from agaritine to yield the reactive free hydrazine, which is further converted to the highly reactive diazonium ion by hepatic microsomes.
Asunto(s)
Riñón/metabolismo , Hígado/metabolismo , Fenilhidrazinas/metabolismo , Animales , Basidiomycota/química , Biotransformación , Bovinos , Relación Dosis-Respuesta a Droga , Masculino , Ratones , Pruebas de Mutagenicidad , Ratas , Ratas Sprague-Dawley , gamma-Glutamiltransferasa/metabolismoRESUMEN
The title compound is a strong carcinogen, similar in potency to benzo[a]pyrene in mouse skin assay. This paper describes a comparison of its in vitro metabolism by hepatic microsomal preparations from mouse, rat, rabbit, hamster, dog, monkey and man. Metabolites were isolated by preparative high pressure liquid chromatography from the ethyl acetate extractable material and their structures tentatively assigned on the basis of their retention times and ultraviolet spectra, when possible by direct comparison with authentic synthetic specimens. Mass spectrometry was then used to confirm these assignments. All these animals produce the same range of metabolites derived exclusively from oxidation at the benzo-ring A, the five-membered ring D, and at the 11-methyl group. However, the amounts of individual metabolites varied substantially. In particular all the animals yielded the proximate carcinogen 3,4-dihydroxy-11-methyl-3,4,15, 16-tetrahydrocyclopenta[a]phenanthren-17-one, from which it is reasoned that all might be susceptible to its carcinogenic action. A rationalization for the observed distribution of the metabolites is proposed on the basis of a molecular model of the active site of cytochrome P450 1A1, the oxidative enzyme involved.
Asunto(s)
Carcinógenos/metabolismo , Gonanos/metabolismo , Microsomas Hepáticos/metabolismo , Animales , Sitios de Unión , Biotransformación , Carcinógenos/química , Cromatografía Líquida de Alta Presión , Cricetinae , Sistema Enzimático del Citocromo P-450/química , Sistema Enzimático del Citocromo P-450/metabolismo , Perros , Gonanos/química , Haplorrinos , Humanos , Ratones , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Conformación Proteica , Conejos , Ratas , Especificidad de la EspecieRESUMEN
The increase in carcinogenicity of polycyclic aromatic compounds following bay-region methyl group substitution involves a steric component: increasing the size of the alkyl substituent decreases the carcinogenic activity of the compound. To determine whether there is also an electronic component to this effect, we synthesized a bay-region 11-trifluoromethyl analogue of 15,16-dihydrocyclopenta[alpha]phenanthren-17-one which is sterically similar but electronically very different from the 11-methyl derivative. This trifluoromethyl derivative bound to DNA in cultures of the human mammary carcinoma cell line MCF-7 to a much lower extent than the methyl-substituted compound. The trifluoromethyl derivative did not form detectable levels of DNA adducts in the epidermis of Sencar mice and was inactive as an initiator after promotion with 12-O-tetradecanoylphorbol-13-acetate for 20 weeks. In contrast, the 11-methyl derivative formed > 3 pmol adducts/mg DNA and initiated eight papillomas per mouse. These data indicate that both the steric configuration and the electronic nature of a bay-region substituent are important in determining the overall effect of the substituent on the biological activity of the molecule.
Asunto(s)
Carcinógenos/metabolismo , Carcinógenos/toxicidad , Aductos de ADN/metabolismo , ADN/metabolismo , Gonanos/metabolismo , Gonanos/toxicidad , Neoplasias Cutáneas/inducido químicamente , Animales , Neoplasias de la Mama , Línea Celular , Epidermis/efectos de los fármacos , Epidermis/metabolismo , Epidermis/patología , Femenino , Humanos , Metilación , Ratones , Ratones Endogámicos SENCAR , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/patología , Relación Estructura-Actividad , Acetato de Tetradecanoilforbol/toxicidad , Factores de Tiempo , Células Tumorales CultivadasRESUMEN
The present study was undertaken in order to rationalise the apparent biological inactivity of 15,16-dihydro-6-methylcyclopenta[a]phenanthren-17- one (4) when other methyl isomers of 15,16-dihydrocyclopenta[a]phenanthren- -17-one, e.g. the 11-methyl derivative (2), display appreciable tumorigenicity. In vitro metabolism of the 6-methyl-ketone-17-one (4) demonstrated that its principal metabolite was the 3,4-dihydro-3,4-diol (3,4-dihydroxy-6-methyl-3,4,15,16- tetrahydrocyclopenta[a]phenanthren-17-one) (5) which, in the case of the active 11-methyl derivative, is the proximate genotoxin. Thus the inactivity of this 6-methyl-17-ketone cannot be ascribed to lack of formation of the 3,4-dihydro-3,4-diol, the precursor of the 3,4-diol-1,2-epoxides (the ultimate mutagens in this series). However, the 6-methyl-3,4-dihydro-3,4-diol exists in a pseudo-diaxial rather than a pseudo-diequatorial conformation characteristic of the 3,4-dihydro-3,4-diols of the other members of the series. It is therefore suggested that a diequatorial conformation in the dihydrodiol is essential to the metabolic activation of the cyclopenta[a]phenanthren-17-ones.
Asunto(s)
Gonanos/metabolismo , Gonanos/toxicidad , Mutágenos/metabolismo , Mutágenos/toxicidad , Animales , Biotransformación , Técnicas In Vitro , Masculino , Microsomas Hepáticos/metabolismo , Conformación Molecular , Ratas , Ratas Wistar , Relación Estructura-ActividadRESUMEN
A series of four 11-alkoxy cyclopenta[a]phenanthren-17-ones, ranging from the methoxy to the butoxy derivative, has been synthesised in order to investigate the effect of the size of the 11-substituent on the mutagenicity and ability of these compounds to induce hepatic CYP1 activity in rats. The latter was monitored by using as diagnostic probes methoxy and ethoxy-resorufin, and immunologically in Western blots employing anti-CYP1A1 antibodies. All four members of the series induced both CYP1A1 and CYP1A2 activities and apoprotein levels, but the methoxy- and ethoxy-CPP-17-ones were clearly the most potent. Of the four isomers, only 11-methoxy-CPP-17-one displaced 3H-TCDD from the cytosolic Ah receptor. Similarly only 11-methoxy-CPP-17-one elicited a positive mutagenic response in the Ames test in the presence of an Aroclor 1254-induced activation system. The relevance of these findings to the carcinogenicity of these compounds in the mouse skin painting model is discussed.
Asunto(s)
Sistema Enzimático del Citocromo P-450/efectos de los fármacos , Gonanos/toxicidad , Hígado/metabolismo , Mutágenos/toxicidad , Fenantrenos/toxicidad , Compuestos Policíclicos/metabolismo , Animales , Citocromo P-450 CYP1A2 , Sistema Enzimático del Citocromo P-450/inmunología , Sistema Enzimático del Citocromo P-450/metabolismo , Hígado/efectos de los fármacos , Hígado/enzimología , Masculino , Pruebas de Mutagenicidad , Oxidorreductasas/efectos de los fármacos , Oxidorreductasas/metabolismo , Ratas , Ratas Wistar , Salmonella/efectos de los fármacos , Salmonella/genética , Relación Estructura-ActividadRESUMEN
An analysis has been made of the C-H...O interactions in cyclopenta[a]phenanthrenes, for which structural data on fifteen 15,16-dihydrocyclopenta[a]-phenanthren-17-ones are available. These compounds mostly contain only one O atom, a carbonyl group at the 17-position, and therefore the only groups available for interactions are C-H groups. In addition, the crystal structure of a second polymorph of the 11-ethyl derivative is described. M(r) = 260.33, Pbca, a = 17.012 (2), b = 21.042 (2), c = 7.6465 (6) A, V = 2737.2 (4) A, Z = 8, Dx = 1.264 Mg m-3, Cu K alpha, lambda = 1.5418 A, mu = 0.56 mm-1, F(000) = 1104, T = 295 K, final R = 0.090 for 1669 reflections above 2 sigma (F). The conformation of the ethyl group is gauche [C(12)-C(11)-C(18)-C(19) = 75.8 (7) degrees], differing from the cis value of -1.3 (5) degrees for the Pnaa form. The molecular distortion in the Pbca polymorph is also larger than that in the Pnaa polymorph; this distortion is evidenced by torsion angles (13-20 degrees) in the bay region and by an out-of-plane displacement (0.8 A) of the C atom of the methylene portion of the ethyl group [the C atom attached to C(11)]. Packing diagrams and intermolecular distances were analyzed for all the dihydrocyclopenta[a]phenanthrenes for which structural data are available. There appear to be three types of packing. The first type consists of a dimer herringbone formed by the interactions of two molecules by way of the ketone group and the C-H of C(12) of the adjacent ring. The second type of packing also involves a dimer but involves C-H and O-C groups at either ends of the molecule. The third type is a layer structure and involves compounds that crystallize with a unit-cell length of 7.5-7.6 A (or, in a very planar structure, 13.8 A). The translational stacking (approximately 4 A apart) found in polycyclic aromatic hydrocarbons is not observed in the crystal structures of these dihydrocyclopenta[a]-phenanthrenes because of the bulk of methyl or methylene groups and the dipole moment of the carbonyl group.
Asunto(s)
Fenantrenos/química , Cristalografía por Rayos X , Conformación Molecular , Estructura Molecular , Relación Estructura-ActividadRESUMEN
Methylation of the non-carcinogen 15,16-dihydrocyclopenta[a]phenanthren-17-one (CPP-17-one) at the bay region to form 11-CH3-CPP-17-one confers carcinogenic potential. In the present study we have investigated the in vitro metabolism and mutagenicity of the methylated compound by hepatic microsomal preparations from rats pretreated with various prototype inducers of cytochrome P450 proteins in order to provide a rationale for this marked difference in carcinogenic activity. The most effective metabolism of 11-CH3-CPP-17-one occurred in the presence of Aroclor 1254-induced microsomes, the principal metabolites being oxidative products of the A- and D-rings and of the methyl substituent. When benzo[a]pyrene-induced microsomes served as the metabolising system, the major A-ring metabolite was the 3,4-diol. A similar metabolic pattern was seen with microsomes from rats treated with 11-CH3-CPP-one itself, but the overall effect of metabolism was lower than that observed with benzo[a]pyrene-treated microsomes but higher than that of control animals. In contrast, microsomes from rats treated with clofibrate, dexamethasone, isoniazid and phenobarbitone failed to enhance the metabolism of 11-CH3-CPP-17-one when compared with control microsomes and the metabolites reflected primarily oxidation of the D-ring. When 11-CH3-CPP-17-one was employed as a promutagen in the Ames test, a mutagenic response was evident only in the presence of microsomes from benzo[a]pyrene-induced rats, but induction with phenobarbitone, isoniazid, dexamethasone, clofibrate and the compound itself, failed to elicit a positive mutagenic response. When 3,4-dihydroxy-11-CH3-CPP-17-one served as the promutagen, a mutagenic response was observed in the presence of benzo[a]pyrene-induced and, to a lesser extent, 11-CH3-CPP-17-one-induced microsomes. Treatment of rats with 11-CH3-CPP-17-one caused a marked increase in the O-deethylation of ethoxyresorufin and, to a much lesser extent in epoxide hydrolase activity. It is concluded that (i) 11-CH3CPP-17-one is an inducer of the CYP1 family; (ii) under the present experimental conditions only the CYP1 family can oxidise the A-ring to form the 3,4-dihydroxy-11-CH3-CPP-17-one, the precursor of the ultimate carcinogen and (iii) only the CYP1 family oxidizes the diol to generate the ultimate carcinogen.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Sistema Enzimático del Citocromo P-450/metabolismo , Gonanos/metabolismo , Microsomas Hepáticos/metabolismo , Animales , Arocloros , Inducción Enzimática/efectos de los fármacos , Gonanos/química , Masculino , Microsomas Hepáticos/efectos de los fármacos , Mutación , Oxidación-Reducción , Ratas , Ratas Wistar , Espectrofotometría UltravioletaRESUMEN
A strongly electronegative, bay-region analogue of the potent carcinogen 15,16-dihydro-11-methylcyclopenta[a]phenanthren-17-one, namely 15,16-dihydro-11-trifluoromethylcyclopenta[a]phenanthren-17-one, is mutagenic to Salmonella typhimurium TA100. Also it is metabolized at the 1,2- and 3,4-positions in the A-ring as well as C-15 in the D-ring to give 3,4-dihydroxy-3,4,15,16-tetrahydro-11-trifluoromethyl- cyclopenta[a]phenanthren-17-one as the only mutagenic metabolite. In these respects its behaviour is closely similar to that of the 11-methyl compound, suggesting that the electronic nature of the bay-region substituent is rather less critical than its spatial configuration in influencing metabolism to genotoxic intermediates. It remains to be seen, however, whether the trifluoromethyl compound is also a carcinogen.
Asunto(s)
Carcinógenos/farmacocinética , Gonanos/farmacocinética , Mutágenos/farmacocinética , Animales , Biotransformación , Carcinógenos/toxicidad , Gonanos/toxicidad , Espectrometría de Masas , Microsomas Hepáticos/metabolismo , Pruebas de Mutagenicidad , Mutágenos/toxicidad , Ratas , Espectrofotometría UltravioletaRESUMEN
Putative synthetic metabolites of the hydrocarbon 16,17-dihydro-15H-cyclopenta[a]phenanthrene and its carcinogenic 11-methyl analogue, namely trans-3,4-dihydroxy-3,4,16,17-tetrahydro-15H- cyclopenta[a]phenanthrene and its 11-methyl derivative, together with the four associated trans-3,4-dihydroxy-syn- and anti-1,2-epoxides, were assayed for mutagenicity in the Ames test with Salmonella typhimurium TA100 with and without microsomal activation. The hydrocarbons were weakly mutagenic and the 3,4-diols were more strongly so, but all required activation to express their mutagenic potential. All four diol-epoxides were much more potent mutagens, even in the absence of activation. This is in accord with the anticipated metabolic activation sequence: hydrocarbons-->3,4-diols-->3,4-diol-1,2-epoxides.
Asunto(s)
Carcinógenos , Mutágenos , Fenantrenos/toxicidad , Animales , Técnicas In Vitro , Masculino , Microsomas Hepáticos/metabolismo , Pruebas de Mutagenicidad , Fenantrenos/química , Fenantrenos/metabolismo , Ratas , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/genética , Relación Estructura-ActividadRESUMEN
The in vitro metabolism and activation to mutagens of 15,16-dihydrocyclopenta[a]phenanthren-17-one (CPP-17-one) were investigated using hepatic preparations from rats pretreated with prototype inducers of the cytochrome P-450-dependent mixed-function oxidases. Aroclor 1254-induced microsomes were the most effective metabolisers of this compound, the major metabolites being oxidation products of the bay region A ring. To a lesser extent hydroxylation of the non-aromatic D ring occurred, the products being the 15- and 16-hydroxyderivatives. Oxidation of the A ring was also achieved with microsomes from benzo[a]pyrene-treated rats but not with those from rats treated with clofibrate, phenobarbitone, isoniazid, dexamethasone and CPP-17-one itself, where the metabolites were primarily the oxidation products of the D ring. When CPP-17-one was used as a promutagen in the Ames test, only microsomes from Aroclor 1254-treated rats could elicit a positive mutagenic response. When 3,4-dihydrodihydroxy-CPP-17-one, the precursor of the ultimate mutagen, was used as the promutagen, a positive response was observed with microsomes from Aroclor 1254- and benzo[a]pyrene-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Sistema Enzimático del Citocromo P-450/metabolismo , Gonanos/metabolismo , Microsomas Hepáticos/metabolismo , Animales , Arocloros/farmacología , Biotransformación/efectos de los fármacos , Carcinógenos/toxicidad , Gonanos/toxicidad , Hidroxilación , Técnicas In Vitro , Masculino , Microsomas Hepáticos/efectos de los fármacos , Pruebas de Mutagenicidad , Ratas , Ratas WistarRESUMEN
The most potent carcinogen of the cyclopenta[a]phenanthrene series, 15, 16-dihydro-11-methylcyclopenta[a]phenanthren-17-one and its non-carcinogenic, unmethylated parent compound, were compared for their abilities to induce micronuclei in epidermal keratinocytes after application onto the dorsal skin of Skh/HR-1 hairless mice. Although both substances were shown to be mutagenic in vitro, only the 11-methyl derivative has been proven to initiate cancer in TO and Sencar mouse strains. In the present study, only the 11-methyl derivative was active as a cancer initiator in Skh/HR-1 mice. For studying micronucleus induction, a preliminary experiment was conducted to establish doses of both chemicals that allowed cell survival. Subsequently, micronucleus induction in epidermal keratinocytes was shown to agree with the cancer-initiating potential of the two compounds. Only the carcinogenic derivative induced a statistically significant increase in micronuclei, over the range 10-100 nmol. This is considerably lower than the dose of approximately 1600 nmol commonly used to initiate skin cancer in mice, but is comparable to the active dose range for skin micronucleus induction by benzo[a]pyrene, a chemical of equivalent carcinogenic potency.
Asunto(s)
Gonanos/toxicidad , Papiloma/inducido químicamente , Neoplasias Cutáneas/inducido químicamente , Animales , Queratinocitos/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos , Ratones Desnudos , Pruebas de MicronúcleosRESUMEN
The hypothesis has been put forward that mutagenic polycyclic aromatic hydrocarbons which induce the P-450 I family of cytochromes, the major enzyme system responsible for their activation, are likely to be carcinogenic. In order to test this hypothesis, rats have been pretreated with a number of polycyclic aromatic hydrocarbons of different mutagenic and carcinogenic potency and hepatic P-450 I activity was monitored using chemical probes such as the O-deethylation of ethoxyresorufin and metabolic activation of Glu-P-1 to mutagens, and immunologically employing polyclonal antibodies against purified rat P-450 I A1. All compounds studied enhanced P-450 I activity and induced P-450 I apoproteins but the extent of induction was very markedly different. The results are discussed with reference to the mutagenicity of these chemicals in the Ames test and their carcinogenicity in the classical mouse skin model. A relationship appears to exist between carcinogenicity of polycyclic aromatic hydrocarbons and their ability to induce hepatic P-450 I activity.
Asunto(s)
Carcinógenos/farmacología , Sistema Enzimático del Citocromo P-450/biosíntesis , Microsomas Hepáticos/efectos de los fármacos , Compuestos Policíclicos/farmacología , Animales , Benzo(a)pireno/farmacología , Benzopirenos/farmacología , Biotransformación , Pruebas de Carcinogenicidad , Crisenos/farmacología , Inducción Enzimática/efectos de los fármacos , Gonanos/farmacología , Masculino , Microsomas Hepáticos/enzimología , Oxigenasas de Función Mixta/metabolismo , Pruebas de Mutagenicidad , Ratas , Ratas Endogámicas , Relación Estructura-ActividadRESUMEN
The present study was designed to compare the skin tumor promoting and epidermal ornithine decarboxylase (ODC) inducing activities of various structural analogs of anthralin (1,8-dihydroxy-9-anthrone) and chrysarobin (1,8-dihydroxy-3-methyl-9-anthrone). Groups of 30 SENCAR mice each were initiated with 7,12-dimethylbenz[a]anthracene and 2 weeks later promoted with once- or twice-weekly applications of various doses of these anthrone derivatives. Carbon-10 (C10)-acyl derivatives of anthralin were active skin tumor promoters in the range of 25-440 nmol per mouse. 10-Acetylanthralin was significantly more active than 10-myristoyl-anthralin at low doses (e.g. 25 and 50 nmol per mouse) and nearly as potent as the unsubstituted compound. Higher doses (greater than or equal to 100 nmol per mouse) of this derivative were toxic, hence, reducing the final papilloma response. On a relative activity scale where anthralin is 1.0, these derivatives had activities that were approximately 0.7 and 0.2, respectively. 10,10-Dipropylanthralin was totally inactive at the doses tested. C6-Substituted derivatives of chrysarobin demonstrated diverse tumor promoting activities when tested in the range of 25-440 nmol per mouse. On a relative activity scale where chrysarobin is 1.0, 6-methoxychrysarobin (physcion anthrone) was approximately 0.9, whereas 6-hydroxychrysarobin (emodin anthrone) had no activity. Chrysophanic acid (1,8-dihydroxy-3-methyl-9,10-anthraquinone) was also inactive as a tumor promoter at the doses tested. In general, the tumor promoting activities of these anthrone derivatives correlated very well with their ability to induce epidermal ODC after a single topical application indicating an important role for this enzyme in skin tumor promotion by anthones. The ability of C10-substituted derivatives of anthralin to undergo base catalyzed oxidation in vitro correlated with both ODC inducing and tumor promoting activities. In addition, copper(II)bis(diisopropylsalicylate) was found to inhibit both ODC induction and skin tumor promotion by chrysarobin. These latter data, when taken together, suggest a role for oxidation at C10 in skin tumor promotion by anthrone derivatives.
Asunto(s)
Antracenos/toxicidad , Antralina/análogos & derivados , Ornitina Descarboxilasa/biosíntesis , Neoplasias Cutáneas/inducido químicamente , Piel/enzimología , Animales , Antracenos/metabolismo , Antralina/metabolismo , Antralina/toxicidad , Inducción Enzimática/efectos de los fármacos , Femenino , Radicales Libres , Ratones , Salicilatos/farmacología , Relación Estructura-ActividadRESUMEN
Two newly synthesized cyclopenta[a]phenanthrenes, namely the 1-methyl (VIII) and 7,11-dimethyl (VII) derivatives of the parent ketone 15,16-dihydrocyclopenta[a]phenanthren-17-one (I), have been tested for their capacity to produce skin tumors in mice. The former (VIII) is essentially inactive, whereas the latter (VII) is very potent in both repeated application and two-stage tests. X-ray crystallographic structure analyses have been carried out on seven derivatives of (I), namely its 11-methyl (II), 11,12-dimethyl (III), 11-methoxy (V), 11-ethyl (VI) and 7,11-dimethyl (VII) analogues (carcinogens), the 1-methyl derivative (VIII), and 11,12,15,16-tetrahydro-11-methyl-17-oxocyclopenta[a]phenanthrene (IV) (both non-carcinogens). The detailed molecular structures resulting from these studies have shown the effects of steric interactions and substitutions on the bay-region geometry. The methyl group on C(11) causes distortions of the molecule in the bay region. Out-of-plane distortions in the bay regions of the 11-methyl derivatives (II, III, VII) are greater than for the 11-methoxy or the 11-ethyl derivatives (V, VI). Molecules (except for III and IV) are packed in the crystals with interactions that include C = O...H interactions; this packing is in layers that are nearly parallel to each other. A hydrogen atom of the 11-methyl group appears, from computer modeling, to interact sterically with the hydrogen atom of the bay-region expoxide group in the activated diol-epoxide; this steric interaction may force one conformer of the diol-epoxide to be the predominant form, thereby accounting for the importance of a bay-region methyl group. Further computer modeling has been used to analyze possible modes of interaction of the diol-epoxides of cyclopenta[a]phenanthrenes with DNA.