Sensitivity of drosophila mutants to chemical carcinogens.

7 single-mutant and five double-mutant strains of Drosophila melanogaster were tested for their relative sensitivity to the chemical carcinogens: 1-acetylaminofluorene, benzo(alpha)pyrene, N-methyl-N'-nitro-N-nitrosoguanidine, 4-nitro quinoline-1-oxide and aflatoxin B1. Among the single mutants, mei-9a, mei-41D5 and mus(1)104D1 are hypersensitive to all 5 chemicals, whereas mus(1)107D1 is hypersensitive only to 4-nitroquinoline-1-oxide and is slightly sensitive to benzo(alpha)pyrene. The mei-9a mei-41D5 double-mutant is the most sensitive of 5 tested double-mutants which carry the mei-9a allele. When treated with 0.025 mM benzo(alpha)pyrene this double-mutant produces significantly more sex-linked recessive lethals and dominant lethals than does the control. Analysis of double-mutants reveals that the mei-9+ product functions in a different repair pathway of methyl methanesulfonate-induced damage than do the normal products of the mus(1)103, mus(1)104 and mus(1)107 loci. Our findings suggest that the sensitivity of Drosophila repair-deficient mutants could be exploited in screening for potential mutagens and carcinogens.     

Isolation and characterization of second chromosome mutagen-sensitive mutations in Drosophila melanogaster

We have undertaken the study of a collection of 32 Drosophila melanogaster mus strains selected on the basis of developmental sensitivity to the DNA-damaging agents, methyl methanesulfonate (MMS), N-acetyl-2-aminofluorene (AAF), nitrogen mustard (HN2), and gamma-radiation. In total, 18 of these strains are sensitive to MMS. In turn, 14 of these exhibit unconditional MMS sensitivity (one of the latter mutants is lethal at 29 degrees C), whereas the other 4 are sensitive to MMS only at higher temperatures. Detailed analysis of the 7 strongest MMS-sensitive strains reveals that they identify 4 new second chromosome mus loci. Two mus loci are each represented by two alleles. One mutant (mus205B1) is allelic to a previously characterized mus locus. Different MMS-sensitive mutants display patterns of mutagen cross-sensitivity (to AAF, HN2, benzo[a]pyrene (BP), and gamma-rays) that parallel the range of responses seen in previously recovered X-linked and autosomal mus loci. In general, mutations that are strongly sensitive to MMS are also sensitive to one or both of the procarcinogens, AAF and BP, as opposed to HN2 and gamma-radiation. In contrast, the moderately MMS-sensitive mutations are sensitive to HN2 and gamma-rays, but not to AAF or BP. Of the 14 mus strains that are not sensitive to MMS, 5 are sensitive to AAF, another 5 are sensitive to HN2, and the remaining 4 are sensitive to gamma-rays.     

Physiological characterization of Mycobacterium sp. strain 1B isolated from a bacterial culture able to degrade high-molecular-weight polycyclic aromatic hydrocarbons

AIM: The aim of this study was to further characterize a bacterial culture (VUN 10,010) capable of benzo[a]pyrene cometabolism. METHODS AND RESULTS: The bacterial culture, previously characterized as a pure culture of Stenotrophomonas maltophilia (VUN 10,010), was found to also contain another bacterial species (Mycobacterium sp. strain 1B), capable of degrading a similar range of PAH substrates. Analysis of its 16S rRNA gene sequence and growth characteristics revealed the strain to be a fast-growing Mycobacterium sp., closely related to other previously isolated PAH and xenobiotic-degrading mycobacterial strains. Comparison of the PAH-degrading characteristics of Mycobacterium sp. strain 1B with those of S. maltophilia indicated some similarities (ability to degrade phenanthrene and pyrene), but some differences were also noted (S. maltophilia able to degrade fluorene, but not fluoranthene, whereas Mycobacterium sp. strain 1B can degrade fluoranthene, but not fluorene). Unlike the S. maltophilia culture, there was no evidence of benzo[a]pyrene degradation by Mycobacterium sp. strain 1B, even in the presence of other PAHs (ie pyrene) as co-metabolic substrates. Growth of Mycobacterium sp. strain 1B on other organic carbon sources was also limited compared with the S. maltophilia culture. CONCLUSIONS: This study isolated a Mycobacterium strain from a bacterial culture capable of benzo[a]pyrene cometabolism. The Mycobacterium strain displays different PAH-degrading characteristics to those described previously for the PAH-degrading bacterial culture. It is unclear what role the two bacterial strains play in benzo[a]pyrene cometabolism, as the Mycobacterium strain does not appear to have endogenous benzo[a]pyrene degrading ability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the isolation and characterization of a novel PAH-degrading Mycobacterium strain from a PAH-degrading culture. Further studies utilizing this strain alone, and in combination with other members of the consortium, will provide insight into the diverse roles different bacteria may play in PAH degradation in mixed cultures and in the environment.     

Micronucleus test with benzo[a]pyrene using a single peroral administration and intraperitoneal injection in males of the MS/Ae and CD-1 mouse strains

The effect of route of administration on the outcome of the micronucleus test was examined by administering benzo[a]pyrene (B[a]P) perorally (p.o.) and intraperitoneally (i.p.) to males of the MS/Ae and CD-1 mouse strains. This study consisted of 3 parts. First, an acute toxicity study lasting 3 days was done to estimate LD50s. The LD50 was larger than 1600 mg/kg for both routes in the 2 strains. Second, pilot micronucleus tests were carried out, on the basis of which an appropriate sampling time (48 h) and dose levels (62.5, 125, 250, and 500 mg/kg) were chosen for both routes and both strains. Third, full-scale micronucleus tests were done, which indicated that (1) B[a]P induced micronuclei dose-dependently by each administration route in each strain, (2) the i.p. route induced frequencies of micronuclei almost equal to or slightly higher than did the p.o. route, and (3) the MS/Ae strain was the higher responder.     

乳杆菌吸附苯并芘的特性

[目的]探讨植物乳杆菌(Lactobacillus plantarum)121和戊糖乳杆菌(Lactobacillus pentosus)ML32的苯并芘吸附作用与机制.[方法]采用高效液相色谱检测菌体对苯并芘的吸附率.[结果]菌株121和ML32对苯并芘的吸附率分别为65.9%和64.9%,这种吸附特性与菌体活力无关,随培养时间延长、温度提高以及细胞浓度的上升而增加.菌株121和ML32的吸附率在pH 4和5时达到最大,分别为87.6%和89.0%.当培养液中Ca2+或Mg2+浓度大于0.05mol/L时,菌体吸附率与盐离子浓度呈正相关.苯洗脱会导致乳杆菌所吸附的苯并芘减少90%.经碱性蛋白酶、中性蛋白酶、溶菌酶及TCA和SDS等方法处理后,菌体吸附率上升,且不易被苯去除.在胆盐及胃酸环境下,两株菌的吸附率均提高至70%以上,而胰蛋白酶的存在仅对菌株121的吸附率有较大影响.[结论]两株乳杆菌可以通过吸附作用从环境中清除苯并芘,其吸附效果与细菌细胞壁的结构和组成有关.     

Rhodanobacter sp. strain BPC1 in a benzo[a]pyrene-mineralizing bacterial consortium

A bacterial consortium which rapidly mineralizes benzo[a]pyrene when it is grown on a high-boiling-point diesel fuel distillate (HBD) was recovered from soil and maintained for approximately 3 years. Previous studies have shown that mobilization of benzo[a]pyrene into the supernatant liquid precedes mineralization of this compound (R. Kanaly, R. Bartha, K. Watanabe, and S. Harayama, Appl. Environ. Microbiol. 66:4205-4211, 2000). In the present study, we found that sterilized supernatant liquid filtrate (SSLF) obtained from the growing consortium stimulated mineralization of benzo[a]pyrene when it was readministered to a consortium inoculum without HBD. Following this observation, eight bacterial strains were isolated from the consortium, and SSLF of each of them was assayed for the ability to stimulate benzo[a]pyrene mineralization by the original consortium. The SSLF obtained from one strain, designated BPC1, most vigorously stimulated benzo[a]pyrene mineralization by the original consortium; its effect was more than twofold greater than the effect of the SSLF obtained from the original consortium. A 16S rRNA gene sequence analysis and biochemical tests identified strain BPC1 as a member of the genus Rhodanobacter, whose type strain, Rhodanobacter lindaniclasticus RP5557, which was isolated for its ability to grow on the pesticide lindane, is not extant. Strain BPC1 could not grow on lindane, benzo[a]pyrene, simple hydrocarbons, and HBD in pure culture. In contrast, a competitive PCR assay indicated that strain BPC1 grew in the consortium fed only HBD and benzo[a]pyrene. This growth of BPC1 was concomitant with growth of the total bacterial consortium and preceded the initiation of benzo[a]pyrene mineralization. These results suggest that strain BPC1 has a specialized niche in the benzo[a]pyrene-mineralizing consortium; namely, it grows on metabolites produced by fellow members and contributes to benzo[a]pyrene mineralization by increasing the bioavailability of this compound.     

Products from the incomplete metabolism of pyrene by polycyclic aromatic hydrocarbon-degrading bacteria

Pyrene is a regulated pollutant at sites contaminated with polycyclic aromatic hydrocarbons (PAH). It is mineralized by some bacteria but is also transformed to nonmineral products by a variety of other PAH-degrading bacteria. We examined the formation of such products by four bacterial strains and identified and further characterized the most apparently significant of these metabolites. Pseudomonas stutzeri strain P16 and Bacillus cereus strain P21 transformed pyrene primarily to cis-4,5-dihydro-4,5-dihydroxypyrene (PYRdHD), the first intermediate in the known pathway for aerobic bacterial mineralization of pyrene. Sphingomonas yanoikuyae strain R1 transformed pyrene to PYRdHD and pyrene-4,5-dione (PYRQ). Both strain R1 and Pseudomonas saccharophila strain P15 transform PYRdHD to PYRQ nearly stoichiometrically, suggesting that PYRQ is formed by oxidation of PYRdHD to 4,5-dihydroxypyrene and subsequent autoxidation of this metabolite. A pyrene-mineralizing organism, Mycobacterium strain PYR-1, also transforms PYRdHD to PYRQ at high initial concentrations of PYRdHD. However, strain PYR-1 is able to use both PYRdHD and PYRQ as growth substrates. PYRdHD strongly inhibited phenanthrene degradation by strains P15 and R1 but had only a minor effect on strains P16 and P21. At their aqueous saturation concentrations, both PYRdHD and PYRQ severely inhibited benzo[a]pyrene mineralization by strains P15 and R1. Collectively, these findings suggest that products derived from pyrene transformation have the potential to accumulate in PAH-contaminated systems and that such products can significantly influence the removal of other PAH. However, these products may be susceptible to subsequent degradation by organisms able to metabolize pyrene more extensively if such organisms are present in the system.     

Polycyclic aromatic hydrocarbon oxidation by the white-rot fungus Bjerkandera sp. strain BOS55 in the presence of nonionic surfactants

The effect of nonionic surfactants on the polycyclic aromatic hydrocarbon (PAH) oxidation rates by the extracellular ligninolytic enzyme system of the white-rot fungus Bjerkandera sp. strain BOS55 was investigated. Various surfactants increased the rate of anthracene, pyrene, and benzo[a]pyrene oxidation by two to fivefold. The stimulating effect of surfactants was found to be solely due to the increased bioavailability of PAH, indicating that the oxidation of PAH by the extracellular ligninolytic enzymes is limited by low compound bioavailability. The surfactants were shown to improve PAH dissolution rates by increasing their aqueous solubility and by decreasing the PAH precipitate particle size. The surfactant Tween 80 was mineralized by Bjerkandera sp. strain BOS55; as a result both the PAH solubilizing activity of Tween 80 and its stimulatory effect on anthracene and pyrene oxidation rates were lost within 24 h after addition to 6-day-old cultures. It was observed that the surfactant dispersed anthracene precipitates recrystallized into larger particles after Tween 80 was metabolized. However, benzo[a]pyrene precipitates remained dispersed, accounting for a prolonged enhancement of the benzo[a]pyrene oxidation rates. Because the endogenous production of H2O2 is also known to be rate limiting for PAH oxidation, the combined effect of adding surfactants and glucose oxidase was studied. The combined treatment resulted in anthracene and benzo[a]pyrene oxidation rates as high as 1450 and 450 mg L-1 d-1, respectively, by the extracellular fluid of 6-day-old fungal cultures.     

Biodegradation of benzo(a)pyrene by a newly isolated Fusarium sp

Benzo(a)pyrene (BaP) is a five-ring polycyclic aromatic hydrocarbon produced by the incomplete combustion of organic materials. It is one of the priority pollutants listed by the US Environmental Protection Agency. This study describes a fungal isolate that is able to biodegrade benzo(a)pyrene. The filamentous fungus, isolated from leaves of Pterocarpus macrocarpus Kurz., was identified as a Fusarium sp. (strain E033). Fusarium sp. E033 was able to survive in the presence of benzo(a)pyrene concentrations up to 1.2 mM (300 mg L(-1)). Biodegradation experiments using 0.4 mM (100 mg L(-1)) benzo(a)pyrene demonstrated that Fusarium sp. E033 was able to degrade 65-70% of the initial benzo(a)pyrene provided, and two transformation products, a dihydroxy dihydro-benzo(a)pyrene and a benzo(a)pyrene-quinone, were detected within 30 days of incubation at 32 degrees C. The factors affecting biodegradation efficiency were also investigated. While increasing aeration promoted better fungal growth and benzo(a)pyrene biodegradation, increasing the glucose concentration from 5 to 50 mM had an adverse effect on biodegradation. Ethanol and methanol, provided at 5 mM to increase benzo(a)pyrene water solubility, increased the fungal biomass yield but did not promote degradation. The Fusarium sp. E033 isolated in this study can tolerate and degrade relatively high concentrations of benzo(a)pyrene, suggesting its potential application in benzo(a)pyrene bioremediation.     

The metabolism of drugs and carcinogens in isolated subcellular fractions of Drosophila melanogaster. II. Enzyme induction and metabolism of benzo[a]pyrene

The effect of various pretreatments on the activities of several drug metabolizing enzymes was investigated in microsomes and postmicrosomal supernatant fractions isolated from whole body homogenates of Drosophila melanogaster larvae of different strains. Pretreatments of larvae with either phenobarbital (PB), β-naphthoflavone (BNF) or a mixture of polychlorinated biphenyls (Aroclor 1254, PCB) for 24 h increased microsomal benzo[a]pyrene (BP) monooxygenase activity 2- to 6-fold in all strains as compared to untreated larvae. A simultaneous increase in the contents of cytochrome P-450 occurred after pretreatment with PB and PCB. Comparison of the turnover rates of BP per molecule of cytochrome P-450 indicated that BP was a poor substrate for control cytochrome P-450 whereas BNF induced a most active hemoprotein for this metabolism. Marked differences in the qualitative pattern of BP metabolites were obtained between microsomes isolated from BNF-treated larvae or rat liver microsomes. 3-Hydroxy-BP (3-OH-BP) was the dominating metabolite with both preparations, while the BP dihydrodiols were formed in minor quantities in Drosophila as compared to rat liver. Metyrapone and SKF 525-A inhibited BP metabolism in microsomes isolated from untreated and BNF treated larvae of all strains. In contrast, α-naphthoflavone (ANF) stimulated the BP monooxygenase activity of microsomes isolated from untreated larvae approx. 3-fold but only slightly influenced the activity of microsomes from BNF treated larvae indicating that the latter species of cytochrome P-450 was less sensitive to ANF.In all strains, PCB and PB treatments approximately doubled microsomal epoxide hydrolase activity and increased cytosolic glutathione-S-transferase activity 25–60%, significant only in strain Berlin K after PB treatment. The activities of epoxide hydrolase and glutathione-S-transferase in control larvae were comparable in the different strains, whereas the content of cytochrome P-450 and BP monooxygenase activity was higher in the Hikone R strain. Variability in the induction response to the various pretreatment was observed among the three strains.     

Antibiotic resistance patterns and plasmids of ruminal strains of Bacteroides ruminicola and Bacteroides multiacidus

Summary Plasmids were recovered and are described from three ruminal Bacteroides strains — 23, 223/M2/7 and 46/5(2). Although all three were originally isolated as Bacteroides ruminicola, 46/5(2) is shown here to be a strain of Bacteroides multiacidus, a species not previously described from the rumen. An 11.7 kbp plasmid present in strain 46/5(2) gave the same digestion pattern with Sal I and Sma I as a plasmid in B. multiacidus subgroup b type strain P208-58. Strains 46/5(2) and P208-58 both showed resistance to tetracycline, as did B. ruminicola strain 223/M2/7. B. multiacidus P208-58, and, to a lesser degree, B. ruminicola 23, showed resistance to ampicillin. Four other strains of B. ruminicola and one of B. multiacidus in which plasmids were not detected were sensitive to both antibiotics. It has still to be established whether these resistance traits are plasmid or chromosomally coded.     

Benzo(a)pyrene pretreatment of Drosophila simulans mutant strain results in the induction of aberrant isoform of cytochrome P-450 with increased capacity to metabolize benzo(a)pyrene]

The basal level of benzo(a)pyrene monooxygenase, epoxide hydrolase and glutathione S-transferase activity as well as the content of cytochrome P-450 were found the same in both compared benzo(a)pyrene (BP) sensitive D. simulans strain 364yv and BP-resistant wild one (Turku). Phenobarbital pretreatment resulted in the same increase level of these enzyme activities in both strains. BP-pretreatment of 364yv flies decreased the amount of the cytochrome P-450 but raised up the turnover of BP per molecule of cytochrome P-450. SDS-polyacrylamide gel electrophoresis of the microsomal proteins from BP-pretreated 364yv flies (but not from Turku) showed an increased hemoprotein content in the 56000 band. The relationship between BP-sensitivity of the strain 364yv and BP-induced aberrant isoform of the cytochrome P-450 has been discussed.     

Biodegradation of polycyclic aromatic hydrocarbons by new isolates of white rot fungi.

Eight rapid Poly R-478 dye-decolorizing isolates from The Netherlands were screened in this study for the biodegradation of polycyclic aromatic hydrocarbons (PAH) supplied at 10 mg liter(-1). Several well-known ligninolytic culture collection strains, Phanerochaete chrysosporium BKM-F-1767, Trametes versicolor Paprican 52, and Bjerkandera adusta CBS 595.78 were tested in parallel. All of the strains significantly removed anthracene, and nine of the strains significantly removed benzo(a)pyrene beyond the limited losses observed in sterile liquid and HgCl2-poisoned fungus controls. One of the new isolates, Bjerkandera sp. strain Bos 55, was the best degrader of both anthracene and benzo(a)pyrene, removing 99.2 and 83.1% of these compounds after 28 days, respectively. Half of the strains, exemplified by strains of the genera Bjerkandera and Phanerochaete, converted anthracene to anthraquinone, which was found to be a dead-end metabolite, in high yields. The extracellular fluids of selected strains were shown to be implicated in this conversion. In contrast, four Trametes strains removed anthracene without significant accumulation of the quinone. The ability of Trametes strains to degrade anthraquinone was confirmed in this study. None of the strains accumulated PAH quinones during benzo(a)pyrene degradation. Biodegradation of PAH by the various strains was highly correlated to the rate by which they decolorized Poly R-478 dye, demonstrating that ligninolytic indicators are useful in screening for promising PAH-degrading white rot fungal strains.     

Biodegradation of polycyclic aromatic hydrocarbons by new isolates of white rot fungi.

Eight rapid Poly R-478 dye-decolorizing isolates from The Netherlands were screened in this study for the biodegradation of polycyclic aromatic hydrocarbons (PAH) supplied at 10 mg liter(-1). Several well-known ligninolytic culture collection strains, Phanerochaete chrysosporium BKM-F-1767, Trametes versicolor Paprican 52, and Bjerkandera adusta CBS 595.78 were tested in parallel. All of the strains significantly removed anthracene, and nine of the strains significantly removed benzo(a)pyrene beyond the limited losses observed in sterile liquid and HgCl2-poisoned fungus controls. One of the new isolates, Bjerkandera sp. strain Bos 55, was the best degrader of both anthracene and benzo(a)pyrene, removing 99.2 and 83.1% of these compounds after 28 days, respectively. Half of the strains, exemplified by strains of the genera Bjerkandera and Phanerochaete, converted anthracene to anthraquinone, which was found to be a dead-end metabolite, in high yields. The extracellular fluids of selected strains were shown to be implicated in this conversion. In contrast, four Trametes strains removed anthracene without significant accumulation of the quinone. The ability of Trametes strains to degrade anthraquinone was confirmed in this study. None of the strains accumulated PAH quinones during benzo(a)pyrene degradation. Biodegradation of PAH by the various strains was highly correlated to the rate by which they decolorized Poly R-478 dye, demonstrating that ligninolytic indicators are useful in screening for promising PAH-degrading white rot fungal strains.     

Drosophila wing-spot test: improved detectability of genotoxicity of polycyclic aromatic hydrocarbons

The somatic mutation and recombination tests (SMART) using eyes or wings in the fruit fly Drosophila melanogaster are flexible and sensitive systems for the detection of genotoxicity of individual chemical compounds and complex mixtures. It is of special interest that adults and larvae possess cytochrome P-450-dependent activation systems able to metabolize most promutagens, e.g., nitrosamines, aflatoxins, pyrrolizidine alkaloids, safrole, etc. The polycyclic aromatic hydrocarbons (PAHs) represent a class of promutagens poorly detectable in Drosophila genotoxicity systems. Therefore, new tester strains for the wing-spot test were constructed by introducing chromosomes 1 and 2 from a wild-type strain with increased cytochrome P-450-dependent metabolism linked to a gene on chromosome 2. Previous investigations with the new strains showed their increased detection capability for diethylnitrosamine. Comparative tests with the 3 PAHs benzo[a]pyrene, benz[a]anthracene and 7,12-dimethylbenz[a]anthracene demonstrate, in a reproducible way, that with the new strains all 3 can be detected as active genotoxic compounds. The dose-response curves for all compounds show a plateau with higher exposures. This is interpreted as indicative of a saturation of the cytochrome P-450-dependent activation systems.     

用EROD研究苯并芘和六氯苯的联合毒性作用

用7-乙氧基异叻唑酮-脱乙基酶(EROD)检测的方法,研究了苯并芘和六氯苯对日本青鳉肝脏EROD酶的比活力的影响。结果表明,苯并芘和六氯苯对EROD酶的比活力均有激活作用,在实验浓度范围内,EROD酶的比活力与两者浓度之间存在剂量-效应关系。苯并芘和六氯苯表现为一定的协同作用。实验同时发现日本青鳉在六氯苯和苯并芘中暴露后,EROD酶的比活力开始有一个短暂的降低,然后持续升高。对六氯苯和苯并芘暴露的最佳时间进行了探讨。     

Metabolic activation of heterocyclic amines and other procarcinogens in Salmonella typhimurium umu tester strains expressing human cytochrome P4501A1, 1A2, 1B1, 2C9, 2D6, 2E1, and 3A4 and human NADPH-P450 reductase and bacterial O-acetyltransferase

We investigated roles of different forms of cytochrome P450 (P450 or CYP) in the metabolic activation of heterocyclic amines (HCAs) and other procarcinogens to genotoxic metabolite(s) in the newly developed umu tester strains Salmonella typhimurium (S. typhimurium) OY1002/1A1, OY1002/1A2, OY1002/1B1, OY1002/2C9, OY1002/2D6, OY1002/2E1 and OY1002/3A4, which express respective human P450 enzymes and NADPH-cytochrome P450 reductase (reductase) and bacterial O-acetyltransferase (O-AT). These strains were established by introducing two plasmids into S. typhimurium TA1535, one carrying both P450 and the reductase cDNA in a bicistronic construct under control of an IPTG-inducible double tac promoter and the other, pOA102, carrying O-AT and umuC"lacZ fusion genes. Expression levels of CYP were found to range between 35 to 550 nmol/l cell culture in the strains tested. O-AT activities in different strains ranged from 52 to 125 nmol isoniazid acetylated/min/mg protein. All HCAs tested, and 2-aminoanthracene and 2-aminofluorene exhibited high genotoxicity in the OY1002/1A2 strain, and genotoxicity of 2-amino-3-methylimidazo [4,5-f]quinoline was detected in both the OY1002/1A1 and OY1002/1A2 strains. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]-indole and 3-amino-1-methyl-5H-pyrido[4,3-b]-indole were activated in the OY1002/1A1, OY1002/1B1, OY1002/1A2, and OY1002/3A4 strains. Aflatoxin B(1) exhibited genotoxicity in the OY1002/1A2, OY1002/1A1, and OY1002/3A4 strains. beta-Naphthylamine and benzo[a]pyrene did not exhibit genotoxicity in any of the strains. These results suggest that CYP1A2 is the major cytochrome P450 enzyme involved in bioactivation of HCAs.     

The effect of complete carcinogens on intercellular transfer of lucifer yellow in fibroblast culture

Summary The effect on permeability of gap junctions of complete powerful carcinogens, 3-methylcholanthrene (MC), 7, 12-dimethylbenz(a)anthracene (DMBA), ethyl methanesulfonate (EMS), and weak carcinogens, benz(a)anthracene (BA), benzo(e)pyrene (B(e)P) as well as the arylhydrolase inhibitor 7,8-benzoflavone (7,8-BF) has been studied with the use of a dye-coupling technique and transformed Djungarian hamster DM15 fibroblasts. MC, EMS and 7,8-BF were found to exert a strong inhibitory effect on cell-to-cell dye transfer. BA and DMBA had the uncoupling activity only in 2 out of 4 experiments. B(e)P was not shown to affect LY transfer between DM15 cells. The uncoupling effect of MC, 7,8-BF and EMS (only when EMS used at the concentration of 600 µg/ ml but not 1000 µ/ ml) appeared reversible. The causes of failure to detect DMBA and B(e)P effects on gap junctions are discussed.Abbreviations B(a)P benzo(a)pyrene - B(e)P benzo(e)pyrene - BA benz(a)anthracene - 7,8-B,F 7,8-benzoflavone - DMBA 7,12,dimethylbenz(a)anthracene - MC 3-methylcholanthrene - EMS ethyl methanesulfonate - LY Lucifer Yellow - MNNG N-methyl-N-nitro-N-nitrosoguanidine - PAH polycyclic aromatic hydrocarbons     

Metabolism of benzo[a]pyrene: Effect of 3-methylcholanthrene pretreatment on metabolism by microsomes from lungs of genetically “responsive” and ”nonresponsive” mice

The metabolism of [¹⁴C]benzo[a]pyrene by microsomes from the lungs of normal and 3-methylcholanthrene-treated DBA/2J, C57BL/6J, and A/HeJ mouse strains was quantitatively analyzed by high-pressure liquid chromatography. The ratio of dihydrodiols of benzo[a]pyrene to total metabolites formed was greater with lung microsomes than with liver microsomes in all three strains. The ratio of epoxide hydrase to monooxygenase activity in mouse lung was shown to be considerably higher than in mouse liver. Benzo[a]pyrene metabolism by control lung microsomes showed some strain differences. C57BL/6J and A/HeJ mice formed twice as much dihydrodiols as a percentage of total metabolism compared to DBA/2J mice. DBA/2J mice produced somewhat less phenol 2 fraction and considerably more quinone 1 and 2 fractions than the other two mouse strains as a percentage of total metabolism. Treatment of C57BL/6J and DBA/2J mice with 3-methylcholanthrene resulted in a 20-fold increase in the metabolism of benzo[a]pyrene, while A/HeJ mice were induced more than 50-fold. The profiles of metabolites from the 3-methylcholanthrene-induced animals were nearly identical in all three mouse strains.     

Effect of the high polycyclic aromatic hydrocarbon, benzo[a]pyrene, on the lipid content of Fusarium solani

The purpose of the present paper was to study the effect of the high polycyclic aromatic hydrocarbon (PAH), benzo[a]pyrene, on the lipid [fatty acid (FA) and sterol] composition and content of the fungi Fusarium solani and F. oxysporum, respectively recognized as good and poor PAH degraders. The major FAs and the major sterol that characterized the tested Fusarium strains were C16:0, C18:1, C18:2, and ergosterol. Lipid profiles of F. solani remained unchanged with the addition of benzo[a]pyrene in the culture media at all concentrations and duration of treatment. However, in the presence of benzo[a]pyrene, significant decreases in FA content, which reached 18 % in young cultures and 28 % in mature colonies, were registered. Similarly, the sterol content of F. solani was reduced by 27 % in the presence of benzo[a]pyrene. In contrast, no modification in lipid profile and lipid content were observed with F. oxysporum, a strain recognized as a low benzo[a]pyrene degrader.