3-amino-1-4-dimethyl-5h-pyrido(4-3-b)indole and 2-amino-3-methylimidazo(4-5-f)quinoline

The purpose of this study was to investigate the long-term stabilization of the liver S9-fraction that is widely used in genotoxicity assays in order to mimic bio-activating processes of xenobiotics in vitro. A successful long-term stabilization of the S9-fraction meets the growing demand for the construction of a lab independent device for the detection of genotoxic compounds in field studies with an integrated module for the metabolic activation of pre-genotoxic compounds. The carbohydrates sucrose, trehalose and raffinose were tested in different concentrations or mixtures in order to increase the product stability of the S9-fraction during and after freeze-drying. The activity of the freeze-dried S9-samples was evaluated by means of their potential to activate pre-genotoxic compounds. The successful long-term stabilization of enzymes of the rodent liver S9-fraction for 6 weeks at room temperature by freeze-drying in the presence of 250 mM trehalose is presented.

Topics: Animals; Carbolines; Cryoprotective Agents; Freeze Drying; Liver; Quinolines; Raffinose; Rodentia; Sucrose; Temperature; Time Factors; Trehalose

In order to study the mutagenic effects of heterocyclic aromatic amines (HAAs) in cells of human origin, five compounds, namely 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 2-amino-3, 4-dimethyl-imidazo[4,5-f]quinoline (MeIQ), 2-amino-3, 8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx), the pyridoimidazo derivative 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), were tested in micronucleus (MN) assays with a human derived hepatoma (HepG2) cell line. All HAAs caused significant, dose-dependent effects. The activities of IQ, MeIQ, MeIQx and PhIP were similar (lowest effective concentrations 25-50 microM), whereas Trp-P-1 was effective at a dose of >/=2.1 microM. In addition, the HAAs were tested in MN assays with Chinese hamster ovary (CHO) cells and in Salmonella strain YG1024 using HepG2 cell homogenates as an activation mix. In the CHO experiments, positive results were obtained with Trp-P-1 and PhIP, whereas the other compounds were devoid of activity under all experimental conditions. The discrepancy in the responsivity of the two cell lines is probably due to differences in their acetylation capacity: enzyme measurements with 2-aminofluorene as a substrate revealed that the cytosolic acetyltransferase activity in the HepG2 cells is approximately 40-fold higher than that of the CHO cells. In the bacterial assays all five HAAs gave positive results but the ranking order was completely different from that seen in the HepG2/MN experiments (IQ > MeIQ > Trp-P-1 >/= MeIQx >> PhIP) and the mutagenic potencies of the various compounds varied over several orders of magnitude. The order obtained in bacterial tests with rat liver S9 mix was more or less identical to that seen in the tests with HepG2 cell homogenates but the concentrations of the amines required to give positive results were in general substantially lower (10(-5)-10(-1) microM). Overall, the results of the present study indicate that MN/HepG2 tests might reflect the mutagenic effects of HAAs more adequately than other in vitro mammalian cell systems due to the presence of enzymes involved in the metabolic conversion of the amines.

Topics: Amines; Animals; Arylamine N-Acetyltransferase; Carbolines; Carcinogens; Carcinoma, Hepatocellular; Cell Line; Cell Survival; CHO Cells; Cricetinae; Heterocyclic Compounds; Humans; Imidazoles; Liver Neoplasms; Mutagenicity Tests; Mutagens; Quinolines; Quinoxalines; Rats; Salmonella; Tumor Cells, Cultured

Precision-cut liver slices were prepared from male Fischer 344 rats, female CDF1 mice and humans (both male and female subjects). Liver slices were cultured for 24 hr in medium containing [3H]thymidine and either PhIP, IQ, MeIQ, MeIQx, Glu-P-1 or Trp-P-1, and then processed for auto-radiographic evaluation of unscheduled DNA synthesis (UDS). All six cooked food mutagens examined produced concentration-dependent increases in UDS in human liver slices. PhIP was the most potent compound examined, followed by MeIQx, IQ and then MeIQ, Glu-P-1 and Trp-P-1. Significant increases in UDS were observed with PhIP, IQ and MeIQx at concentrations as low as 5 microM in the culture medium. The same rank order of potency was not apparent in either rat or mouse liver slices. In rat liver slices only MeIQ significantly induced UDS, although positive results were obtained with two other genotoxins, namely 2-acetylaminofluorene and aflatoxin B1. Apart from MeIQx, all the cooked food mutagens produced significant increases in UDS in mouse liver slices. This study demonstrates the usefulness of precision-cut liver slices to evaluate species differences in xenobiotic-induced genotoxicity. Both marked compound and species differences in induction of UDS were observed. The data provide further evidence that dietary cooked food mutagens are potential human carcinogens.

Topics: 2-Acetylaminofluorene; Aflatoxin B1; Animals; Autoradiography; Carbolines; Cooking; Culture Techniques; DNA; Dose-Response Relationship, Drug; Female; Humans; Imidazoles; Liver; Male; Mice; Mutagens; Quinolines; Quinoxalines; Rats; Rats, Inbred F344; Structure-Activity Relationship

Antimutagenic and binding properties of 28 strains of Lactobacillus gasseri and 2 strains of Bifidobacterium longum on the mutagenicity of amino acid pyrolysates were investigated in vitro using a streptomycin-dependent (SD510) strain of Salmonella typhimurium TA 98. Four strains of L. acidophilus (SBT0274, SBT1703, SBT10239, and SBT10241) and 1 strain of B. longum (SBT 2928) exhibited the highest percentage of antimutagenicity and binding. These 5 strains were further optimized for other physical factors influencing the mechanism of binding, such as cell and mutagen concentration, pH, and incubation time. In all of the selected strains, 2 mg of cells bound with 88 to 95% of 0.2 mg of 3-amino-1,4 dimethyl-5H-pyrido[4,3-b]indole in 30 min at pH 7.0. Other amino acid pyrolysates, such as 3-amino-1-methyl-5H-pyrido[4,3-b]indole, 2-amino-6-methyldi-pyrido[1,2-a:3',2'-d]imidazole, 2-amino-3-methyl-imidazo[4,5,f]quinoline, and 2-amino-3,4-dimethyl-imidazo[4,5,f]quinoline were also tested for the binding ability of these strains. We observed that the complexity of the mutagens greatly influenced the binding properties. The binding of 3-amino-1,4 dimethyl-5H-pyrido[4,3-b]indole to the purified cell walls was very high compared with that of the crude cell wall, peptidoglycan, or the cell extract. Binding was inhibited when the cell walls were subjected to treatment with metaperiodate or trichloroacetic acid but not when they were subjected to treatment with lysozyme, trypsin, or proteinase K, reflecting the role of the carbohydrate component as a binding site.

Topics: Amino Acids; Antimutagenic Agents; Bifidobacterium; Binding Sites; Carbolines; Cell Wall; Chemical Phenomena; Chemistry, Physical; Hydrogen-Ion Concentration; Imidazoles; Lactobacillus; Mutagens; Periodic Acid; Quinolines; Time Factors; Trichloroacetic Acid

The effects of dietary bioantimutagens (compounds which have been shown to inhibit mutagenesis via interaction with DNA repair processes) on spontaneous and heterocyclic amine (HCA)-induced micronucleus (MN) frequencies were studied in metabolically competent human hepatoma (Hep-G2) cells. All the compounds tested (coumarin, vanillin, caffeine, tannic acid and cinnamaldehyde) caused a moderate increase of MN numbers in Hep-G2 cells at high concentrations (500 microg/ml); only tannic acid was also active at lower dose levels. In combination experiments with the HCA 2-amino-3-methylimidazo-[3,4-f]quinoline (IQ), post-treatment of the cells with bioantimutagens resulted in a pronounced (75-90%) decrease in MN. The most drastic effects were seen with vanillin, coumarin and caffeine which were active at concentrations < or = 5 microg/ml. Further experiments indicated that these compounds also attenuate the mutagenic effects of other HCAs (PhIP, MeIQ, MeIQx, Trp-P-1).

Topics: Acrolein; Amines; Antimutagenic Agents; Benzaldehydes; Caffeine; Carbolines; Carcinoma, Hepatocellular; Coumarins; DNA Repair; Heterocyclic Compounds; Humans; Hydrolyzable Tannins; Imidazoles; Micronucleus Tests; Mutagens; Quinolines; Tumor Cells, Cultured

We used a modification of the alkaline single cell gel electrophoresis (SCG) (Comet) assay to test the in vivo genotoxicity of 6 heterocyclic amines, Trp-P-1 (25 mg/kg), Trp-P-2 (13 mg/kg), IQ (13 mg/kg), MeIQ (13 mg/kg), MeIQx (13 mg/kg) and PhIP (40 mg/kg), in mouse liver, lung, kidney, brain, spleen, bone marrow and stomach mucosa. Mice were sacrificed 1, 3, and 24 h after intraperitoneal injection. Trp-P-2, IQ, MeIQ, and MeIQx yielded statistically significant DNA damage in the stomach, liver, kidney, lung and brain; Trp-P-1 in the stomach, liver and lung; and PhIP in the liver, kidney and brain. None of the heterocyclic amines induced DNA damage in the spleen and bone marrow. Our results suggest that the alkaline SCG assay applied to multiple organs is a good way to detect organ-specific genotoxicity of heterocyclic amines in mammals.

Topics: Amines; Animals; Brain; Carbolines; DNA Damage; Electrophoresis; Imidazoles; Kidney; Liver; Male; Mice; Mice, Inbred Strains; Mutagens; Quinolines; Quinoxalines; Stomach

The antimutagenic effects of methanolic extracts of peanut hulls (MEPH) were evaluated by the Ames test. MEPH inhibited the mutagenicity of 4-nitroquinoline-N-oxide (NQNO), a direct-acting mutagen. MEPH also inhibited the mutagenicity of some indirect-acting mutagens and decreased in the order of 2-amino-3-methyl-imidazo(4,5-f)quinoline (IQ) > aflatoxin B1 (AFB1) > 2-amino-6-methyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-1) > 3 amino-1,4-dimethyl-5H-pyridol(4,3-b)indole (Trp-P-1) > benzo(a)pyrene (B(a)P for S. typhimurium TA98, and IQ > Trp-P-1 > Glu-P-1 > AFB1 > B(a)P for S. typhimurium TA100.

Topics: 4-Nitroquinoline-1-oxide; Aflatoxin B1; Animals; Antimutagenic Agents; Arachis; Benzo(a)pyrene; Carbolines; Imidazoles; Male; Methanol; Mutagenicity Tests; Mutagens; Plant Extracts; Quinolines; Rats; Rats, Sprague-Dawley; Salmonella typhimurium

Male Syrian golden hamsters were exposed for 1 or 2 weeks to smoke produced by commercial non-filter cigarettes for 5 consecutive days in a Hamburg type II smoking machine. Postmitochondrial fractions (S9) prepared from the liver, lungs, and pancreas were used in the Ames liquid incubation assay, in order to assess the effect of cigarette smoke (CS) on the metabolic activation of four groups of procarcinogens. The mutagenic activities of five heterocyclic amines on strain TA98 in the presence of liver S9 mix were induced up to 3.7 times above controls including sham smoke control, while no significant alteration of mutagenicity was observed with 3'-hydroxymethyl-N,N-dimethyl-4-aminoazobenzene and benzo[a]pyrene on TA98 or with N-nirosobis(2-oxopropyl)amine (BOP) on TA100. A similar stimulation of metabolic activation was also observed for 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) with S9 from the lungs but not from the pancreas. The mutagenic potential of 11 carcinogens including aflatoxin B1 (AFB1) and two other heterocyclic amines was also examined using liver S9 from male hamsters pretreated with phenobarbital (PB) or 3-methylcholanthrene (MC). The numbers of revertant colonies were much higher (2-20-fold) in the presence of MC-treated liver S9 than in the presence of PB-treated liver S9, except in the case of AFB1 which showed a higher mutagenicity with PB-induced S9. 7,8-Benzoflavone considerably inhibited the activities of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and Trp-P-1 in the presence of either untreated, MC- or CS-treated liver S9, whereas metyrapone was totally lacking this effect, indicating that cytochrome P450(CYP)1A1/1A2 isoforms of hamster liver are predominantly involved in the metabolic activation of these carcinogens. CS exposure of hamsters might selectively induce hepatic CYP1A2 which cannot activate BOP. Consequently, the present findings could explain, in part, the anticarcinogenic effect of CS on BOP-induced pancreatic tumors in hamsters. The findings further support the idea that CS markedly stimulates the metabolic activation of food-derived carcinogens, which may contribute to the overall carcinogenic effects of cigarette smoking.

Topics: Animals; Carbolines; Carcinogens; Cricetinae; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Enzyme Activation; Enzyme Induction; Male; Mesocricetus; Methylcholanthrene; Microsomes; Mutagenicity Tests; Mutagens; Phenobarbital; Quinolines; Smoking

The ability of phthalic acid, phthalic acid anhydride, and various phthalate esters to enhance the mutagenicity of many amino acid pyrolysates was observed with the Ames test (Salmonella typhimurium TA98), but not the SOS Chromotest. Phthalate enhancement of the mutagenicity of 4-nitroquinoline-1-oxide, 2-nitrofluorene, and benzo[a]pyrene was not observed with either test. The mutagenicity-enhancing ability may be related to the induction of enzymes such as P450IIB, that metabolize amino acid pyrolysates. By quantitative structure activity relationship (QSAR) analysis, a good correlation was observed between the mutagenicity-enhancing activity of phthalates and their octanol-water partition coefficients.

Topics: 1-Octanol; 4-Nitroquinoline-1-oxide; Benzo(a)pyrene; Carbolines; Cytochrome P-450 CYP2B1; Cytochrome P-450 Enzyme System; Drug Synergism; Enzyme Induction; Esters; Fluorenes; Imidazoles; Mutagenesis; Mutagenicity Tests; Mutagens; Octanols; Oxidoreductases; Phthalic Acids; Quinolines; Structure-Activity Relationship; Water

The possible anticlastogenic activity and bio-antimutagenic mechanism of the cultured broth of Saccharomyces cerevisiae 28 were examined using in in vivo and in vitro test systems. In the Ames test with Salmonella typhimurium TA100 (SD-) and in the umu-test with S. typhimurium TA1535/psk1002, the cultured broth of S. cerevisiae 28 showed bio-antimutagenic activity against mutagenicity induced by 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). The cultured broth also showed bio-antimutagenic activity towards reverse mutations induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Escherichia coli B/r WP2 trp-, but not by UV radiation. It is clear that the cultured broth could inhibit base substitution mutations induced by mutagens. Using mitomycin C (MMC) as a mutagen, the micronucleus test (with bone marrow cells of mice) showed anticlastogenic action when the cultured broth was given orally to mice. Micronucleated polychromatic erythrocytes induced by the mutagen were reduced by about 47% by the cultured broth.

Topics: Antimutagenic Agents; Carbolines; Culture Media, Conditioned; DNA Repair; Methylnitronitrosoguanidine; Micronucleus Tests; Mitomycin; Mutagenicity Tests; Mutagens; Point Mutation; Quinolines; Saccharomyces cerevisiae; Salmonella typhimurium; Suppression, Genetic

Purified human red blood cell cytosol was used to activate the heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) into mutagenic intermediate(s) in the Salmonella test. The liquid preincubation method in the presence of strain TA98 was utilized. In order to understand the mechanism involved in this metabolic activation, some modulators were incorporated in the medium. The results suggest that an oxygenated hemoprotein, probably oxyhemoglobin, is involved in the activation into genotoxic intermediate(s).

Topics: Biotransformation; Carbolines; Carcinogenicity Tests; Cytosol; Dose-Response Relationship, Drug; Erythrocytes; Humans; Kinetics; Mutagenicity Tests; Mutagens; Quinolines; Salmonella typhimurium

Most heterocyclic amines formed during the cooking of meat and fish have been shown to form adducts in the livers of rats. Recently, however, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), administered in the diet to Fischer 344 (F344) rats for 4 weeks, was shown to produce the highest levels of adducts in the heart. In the present study 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 2-amino-6-methyldipyrido[1,2-a:1',2'-d]imidazole (Glu-P-1) were given to F344 rats at carcinogenic dose levels (IQ 0.03%, MeIQx 0.04%, Trp-P-1 0.015%, Glu-P-1 0.05%) in the diet for 4 weeks. DNA adducts in the liver and heart were analyzed by 32P-postlabeling. DNA adducts were demonstrated to appear in the hearts of all animals exposed to heterocyclic amines at the following levels: IQ, 1.8 adducts/10(7) nucleotides, MeIQx, 3.8/10(7) ntd, Trp-P-1, 20/10(7) ntd and Glu-P-1, 7.2/10(7) ntd. Values for the heart were 10-20% of the respective liver adduct levels. Heart adducts increased linearly throughout the observed period when MeIQx was administered for up to 40 weeks. When MeIQx feeding was discontinued after 20 weeks and the animals subsequently given the basal diet, the adduct level at 20 weeks did not change during the following 20 weeks. A possible role for heart DNA alterations caused by food-borne heterocyclic amines in the development of age-related myopathies and cardiovascular disease is not inconceivable.

Topics: Administration, Oral; Aging; Amines; Animals; Carbolines; Diet; DNA; DNA Damage; Heart; Imidazoles; Kinetics; Liver; Male; Myocardium; Quinolines; Quinoxalines; Rats; Rats, Inbred F344

Potential synergism between five heterocyclic amines at low doses was evaluated in a medium-term liver bioassay system for carcinogens. F344 male rats were given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg) and then received test compound(s) in their diet for 6 weeks beginning 2 weeks later. Control groups received DEN or test compound(s) alone. All rats were subjected to two-thirds partial hepatectomy at week 3 and killed at week 8. Compounds tested and reported positive were 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1, 150 p.p.m.), 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2, 500 p.p.m), 2-amino-3-methylimidazo[4,5-f]quinoline (MeIQ, 300 p.p.m.), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx, 400 p.p.m.). Groups were given each chemical at the carcinogenic dose, or 1/5 or 1/25 of this. Other groups received the five chemicals in combination, each at the 1/5 or 1/25 levels. Enhancing activity was assessed by quantitative analysis of glutathione S-transferase placental form (GST-P) positive foci, the numbers being significantly increased with all chemicals at the highest dose. Trp-P-1, IQ and MeIQ also exerted positive influence even at the 1/5 dose level. Similar results were obtained regarding areas of foci at the highest dose levels, with the exception of Glu-P-2. An increase was also observed for MeIQ at the 1/5 dose. Additive or synergistic effects between the chemicals were evident in the groups given the five chemicals together at both the 1/5 and 1/25 dose levels, development of GST-P positive foic being increased over the sum totals of individual data for the 1/5 or 1/25 dose groups. Thus, carcinogenicity was predicted for all five heterocyclic amines tested in dose-dependent manner in the present system of 8 weeks duration, synergistic effects being apparent especially at the low dose level.

Topics: Animals; Body Weight; Carbolines; Carcinogens; Drug Synergism; Enzyme Induction; Glutathione Transferase; Imidazoles; Immunohistochemistry; Liver; Liver Neoplasms; Male; Organ Size; Quinolines; Quinoxalines; Rats; Rats, Inbred F344

The effect of chemically-induced diabetes on the hepatic microsomal mixed-function oxidase system and the activation of chemical carcinogens was investigated in animals treated with streptozotocin (STZ). In order to distinguish between the effects of the diabetogenic chemical per se and that of the diabetic state, groups of STZ-treated animals received either nicotinamide simultaneously with STZ to prevent the onset of diabetes, or daily treatment with insulin in order to reverse the effects of diabetes. STZ-treated animals exhibited higher pentoxyresorufin O-dealkylase, ethoxy-resorufin O-deethylase, ethoxycoumarin O-deethylase, aniline p-hydroxylase and NADPH-cytochrome c reductase activities; similarly, increases were seen in cytochrome P-450 and b5 levels. All of these effects were prevented by nicotinamide and, at least partly, antagonised by insulin therapy. Treatment of animals with STZ markedly increased the activation, by liver microsomes in vitro, of Trp-P-1 and Trp-P-2 to mutagens, the effect being totally preventable by nicotinamide and successfully antagonised with insulin therapy. The diabetic animals were similarly more efficient in activating MeIQ but the effect was not preventable by nicotinamide or reversed by insulin. In contrast no changes were seen in the activation of IQ and only a modest increase in the case of MeIQx. It is concluded that diabetes may modulate the metabolic activation of some chemical carcinogens, presumably by changing the ratio of the various cytochrome P-450 isoenzymes.

Topics: Animals; Biotransformation; Carbolines; Carcinogens; Cytochrome P-450 Enzyme System; Diabetes Mellitus, Experimental; Electrophoresis, Polyacrylamide Gel; Insulin; Isoenzymes; Male; Microsomes, Liver; Mixed Function Oxygenases; Molecular Weight; Mutagenicity Tests; Mutagens; Niacinamide; Quinolines; Quinoxalines; Rats; Rats, Inbred Strains

Trp-P-1, Trp-P-2, MeA alpha C, A alpha C, Glu-P-1, Glu-P-2, Lys-P-1, IQ and Phe-P-1 were tested for tumour initiating activity in a two-stage skin carcinogenesis model using 12-O-tetradecanoylphorbol-13-acetate (TPA) as the promoter. The total initiating doses were 20 mg for Trp-P-1, Trp-P-2, Glu-P-1 and Glu-P-2, 40 mg for MeA alpha C and A alpha C, 5 mg for Lys-P-1, 7.5 mg for IQ and 100 mg for Phe-P-1. 7,12-Dimethylbenz[a]anthracene was used as a positive control compound at a total dose of 100 micrograms. All compounds were topically applied twice weekly for 5 weeks on the dorsal skin, and then followed by similar TPA administration for 47 weeks. Trp-P-2 induced skin tumours in 30% of the mice (0.35 tumours/mouse), and Trp-P-1, MeA alpha C and Phe-P-1 in 10-20% (0.20-0.25 tumours/mouse). The smaller amounts of Lys-P-1 and IQ applied induced tumours at an incidence of 10 and 5% respectively. No tumours appeared in the groups treated with test chemicals alone or TPA alone. Statistical analysis according to either the Fisher exact test or Peto trend test revealed significant differences for tumour appearance in the Trp-P-1, Trp-P-2, MeA alpha C and Phe-P-1 followed by TPA groups as compared with that given TPA alone. The data were used to generate ID50 (50% initiating dose) values for each of the compounds.

Topics: Animals; Carbolines; Female; Imidazoles; Mice; Mutagens; Quinolines; Skin Neoplasms; Tetradecanoylphorbol Acetate

The genotoxicity of the cooked-food mutagens 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) was studied by monitoring the induction of DNA repair (unscheduled DNA synthesis; UDS) in primary cultures of rodent hepatocytes. The hepatocytes were derived from male Sprague-Dawley rats or Syrian hamsters by collagenase perfusion and the cells were cultured for 4 hr before being exposed to various concentrations of the mutagens. DNA repair was determined by measuring incorporation of [3H]thymidine into extracted DNA over 17 hr using beta-scintillation counting. Dose-related increases in UDS were clearly seen in hamster hepatocytes treated with MeIQ, IQ and the positive control 2-acetylaminofluorene (AAF), and a weak response was induced by MeIQx and Trp-P-1. In the rat hepatocytes only MeIQ and AAF gave clear positive responses. Furthermore it was noted that all the mutagens displayed a more pronounced UDS response in hamster hepatocytes than in rat cells. Studies of the activation of MeIQ by hepatocytes to a bacterial mutagen suggest that this difference is probably a consequence of the greater capacity of hamster cells to activate the mutagens to genotoxic metabolites.

Topics: Animals; Biotransformation; Carbolines; Cricetinae; DNA; DNA Repair; Liver; Male; Mesocricetus; Mutagens; Quinolines; Quinoxalines; Rats; Rats, Inbred Strains; Species Specificity

Carcinogenicities of mutagenic heterocyclic amines in cooked foods have been tested in CDF1 mice and F344 rats of both sexes. Eight heterocyclic amines--Trp-P-1, Trp-P-2, Glu-P-1, Glu-P-2, MeA alpha C, A alpha C, IQ, and MeIQ--were given to mice and/or rats at 0.02 to 0.08% in the diet continuously. In mice, all heterocyclic amines tested were demonstrated to be carcinogenic. Hepatocellular carcinomas were induced in a high incidence in all groups treated with heterocyclic amines. Hemangioendothelial sarcomas were also induced by Glu-P-1, Glu-P-2, MeA alpha C, and A alpha C. Most hemangioendothelial sarcomas were located in the interscapular brown adipose tissue. In mice given IQ, forestomach and lung tumors were also observed in a high incidence. Carcinogenicity tests on MeIQ are ongoing, and interim data by week 83 show that MeIQ also induces forestomach tumors in addition to liver tumors. In rats, hepatocellular carcinomas were induced by Trp-P-1, Glu-P-1, Glu-P-2, and IQ. In rats given Glu-P-1, Glu-P-2, and IQ, adenocarcinomas in the small and large intestines, squamous cell carcinomas in the Zymbal gland and clitoral gland were also observed in a high incidence.

Topics: Animals; Carbolines; Carcinogens; Female; Food Contamination; Heterocyclic Compounds; Hot Temperature; Imidazoles; Male; Mice; Neoplasms, Experimental; Quinolines; Rats

The heterocyclic amines 2-amino-3-methylimidazo-(4,5-f)-quinoline (IQ) and 2-amino-3,4-dimethylimidazo(4,5-f)-quinoline (Me-IQ) which are formed during broiling (grilling) and cooking of protein-rich food, have previously been shown to be both carcinogenic and mutagenic. In this work IQ and Me-IQ were found to be several hundred-fold more mutagenic in liver than in lung microsomal preparations from uninduced mice and rabbits. IQ has already been found to induce tumors at about the same frequency in liver and lung in mice. Obviously, the discrepancy between the data on carcinogenicity in vivo and mutagenicity in vitro with microsomal preparations from the two organs might in part be due to the lack of detoxification mechanisms in the latter system. Freshly isolated lung cells will better mimic the in vivo situation. With the metabolically active Clara cells, IQ was much more mutagenic than Me-IQ. It has previously been shown that the Clara cells have low capacity for DNA repair. It is tempting to speculate whether the situation in the mouse is in correspondence with that described in the rabbit, in which case the cell data fits well with the in vivo carcinogenesis data.

Topics: Animals; Biotransformation; Carbolines; Cytochrome P-450 CYP1A2; Cytochromes; In Vitro Techniques; Lung; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Microsomes; Microsomes, Liver; Mutagens; Quinolines; Rabbits