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

During grilling of the roast beef the following heterocyclic aromatic amines were found: IQ=200.6 ng 100g(-1), MeIQx=719.8 ng 100 g(-1), MeIQ=532.9 ng 100g(-1), 4.8-diMeIQx=755.4 ng 100 g(-1), norharmane=507.0 ng 100 g(-1), harmane=1952.6 ng 100 g(-1), Phe-P 1=263.7 ng 100 g(-1), Trp-P 2=559.2 ng 100 g(-1), PhIP=1179.8 ng 100 g(-1) and AαC=51.7 ng 100g(-1). Their content was tested by using the method based on alkaline hydrolysis of the sample and the method based on solvent extraction of the grilled meat samples at different temperatures (without hydrolysis). The study showed that the heterocyclic aromatic amines produced during the grilling of beef are in a free form and chemically or physico-chemically bonded. The chemical forms of HAA formed in food have never been studied. For the purpose of the partial confirmation that HAA may be chemically or physico-chemically bonded, grilled beef samples were digested in vitro in model segments of the human digestive tract. Digestive enzymes, particularly proteolytic enzymes caused a statistically significant increase of free HAA determined by using solvent extraction without prior chemical hydrolysis of the sample.

Topics: Amines; Animals; Carbolines; Cattle; Cooking; Digestion; Humans; Hydrolysis; Imidazoles; Male; Meat; Mutagens; Quinolines; Quinoxalines; Solvents

Poly(gamma-glutamic acid) (gamma-PGA), a nontoxic and biodegradable macropolymer, was evaluated for its efficiency in binding three mutagenic heterocyclic amines (HAs), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-p-2), as affected by pH in a batch mode. The maximum HA sorption was attained for pH 3-7 and decreased sharply for pH less than 3. Binding isotherms obtained at pH 2.5 and 5.5 showed different isotherm shapes that belong to S and L types, respectively. The isotherm data at pH 2.5 were well described by a linear form of the Langmuir equation, while at pH 5.5 it showed two distinct curves, which were precisely fitted as multiple Langmuir curves. The deviation of linearity in Scatchard plot proved the multisite HA sorption. The Brunauer-Emmett-Teller equation also fitted better to isotherm data at pH 5.5, suggesting a multisite sorption caused by multimolecular HA layers on gamma-PGA. High HA sorption levels of 1250, 667, and 1429 mg/g at pH 2.5 and 1429, 909, and 1667 mg/g at pH 5.5 were observed for MeIQ, 4,8-DiMeIQx, and Trp-p-2, respectively. Among the HAs studied, the sorption capacity correlated directly with hydrophobicity of HAs and inversely with the number of methyl groups in HA molecules. The plausible binding mechanism of HAs on gamma-PGA may include a combination of hydrophobic, hydrogen-bonding, ionic, and dipole-dipole interactions.

Topics: Adsorption; Carbolines; Chemical Phenomena; Chemistry, Physical; Chromatography, High Pressure Liquid; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Mutagens; Polyglutamic Acid; Quinolines; Quinoxalines

Transgenic mouse assays have revealed that the mouse intestine, despite its resistance to carcinogenesis, is sensitive to the mutagenicity of some heterocyclic amines (HCAs). Little is known, however, about the level and localization of that sensitivity. We assessed the mutagenicity of four orally administered (20 mg/kg per day for 5 days) HCAs-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) hydrochloride, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) acetate-in the intestine of male MutaMice. Two weeks after the last administration, we isolated epithelium from the small intestine, cecum, and colon and analyzed lacZ and cII transgene mutations. PhIP increased the lacZ mutant frequency (MF) in all the samples, and in the small intestine, cII and lacZ MFs were comparable. In the cII gene, G:C to T:A and G:C to C:G transversions were characteristic PhIP-induced mutations (which has also been reported for the rat colon, where PhIP is carcinogenic). In the small intestine, PhIP increased the cII MF to four-fold that of the control, but IQ, MeIQ, and Trp-P-2 did not have a significant mutagenic effect. In the cecum, cII MFs induced by IQ and MeIQ were 1.9 and 2.7 times those in the control, respectively. The MF induced by MeIQ in the colon was 3.1 times the control value. Mutagenic potency was in the order PhIP>MeIQ>IQ; Trp-P-2 did not significantly increase the MF in any tissue. The cecum was the most susceptible organ to HCA mutagenicity.

Topics: Amines; Animals; Bacteriophage lambda; Carbolines; Colon; Heterocyclic Compounds; Imidazoles; Intestine, Small; Intestines; Lac Operon; Male; Mice; Mice, Transgenic; Mutagenicity Tests; Mutagens; Quinolines; Transcription Factors; Viral Proteins

Three recombinant human P450 enzymes, forms 1A1, 1A2, and 1B1, were coexpressed with NADPH-cytochrome P450 reductase in an E. coli lacZ strain suitable for detection of the mutagenicity of heterocyclic and aromatic amines. The resulting strains expressed the recombinant P450 holoenzymes at high levels. MeIQ (2-amino-3,4-dimethylimidazo[4,5-f]quinoline) was activated effectively by P450 1A2, weakly by P450 1A1, and not detectably by P450 1B1. MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) and Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole) were activated by all three enzymes, with form 1A2 the most effective. These strains facilitate analysis of the substrate specificity of human P450 forms that participate in the metabolic activation of carcinogens.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Biotransformation; Carbolines; Catalysis; Cell Transformation, Neoplastic; COS Cells; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP1B1; Cytochrome P-450 Enzyme System; Escherichia coli; Lac Operon; Quinolines; Quinoxalines; Substrate Specificity

The major pathway of bioactivation of procarcinogenic heterocyclic aromatic amines (HCAs) is cytochrome P450 1A2 (CYP1A2)-catalyzed N-hydroxylation and subsequent esterification by O-acetyltransferase (O-AT). We have previously reported that an umu tester strain, Salmonella typhimurium OY1001/1A2, endogenously coexpressing human CYP1A2 and NADPH-P450 reductase (reductase), is able to detect the genotoxicity of some aromatic amines [Aryal et al., 1999, Mutat Res 442:113-120]. To further enhance the sensitivity of the strain toward HCAs, we developed S. typhimurium OY1002/1A2 by introducing pCW"/1A2:hNPR (a bicistronic construct coexpressing human P450 1A2 and the reductase) and pOA102 (constructed by subcloning the Salmonella O-AT gene in the pOA101-expressing umuC"lacZ gene) in S. typhimurium TA1535. In addition, as an O-AT-deficient strain, we developed the OY1003/1A2 strain by introducing pCW"/1A2:hNPR and pOA101 into O-AT-deficient S. typhimurium TA1535/1,8-DNP. Strains OY1001/1A2, OY1002/1A2, and OY1003/1A2 expressed, respectively, about 150, 120, and 140 nmol CYP1A2/l culture (in whole cells), and respective cytosolic preparations acetylated 15, 125, and > or = 0 nmol isoniazid/min/mg protein as the O-AT activities of cytosolic preparations, respectively. We compared the induction of umuC gene expression as a measure of genotoxicity and observed that the OY1002/1A2 strain was more sensitive than OY1001/1A2 strain toward the genotoxicity of 2-amino-1,4-dimethylimidazo[4,5-f]quinol ine(MeIQ), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ),2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx),2-aminoanthracene, 2-amino-6-methyldipyrido[1,2-a::3,2'-d]i midazole,3-amino-1, 4-dimethyl-5H-pyrido[4,3-b]indole, and 3-amino-1-methyl-5H-pyrido[4, 3-a]indole. However, the genotoxicity of MeIQ, IQ, and MeIQx was not detected with the OY1003/1A2 strain. These results indicate that the newly developed strain OY1002/1A2 can be employed in detecting potential genotoxic aromatic amines requiring bioactivation by CYP1A2 and O-acetyltransferase.

Topics: Acetyltransferases; Bacterial Proteins; Carbolines; Carcinogens; Cytochrome P-450 CYP1A2; DNA-Directed DNA Polymerase; Escherichia coli Proteins; Genetic Engineering; Humans; Mutagenicity Tests; Mutagens; NADPH-Ferrihemoprotein Reductase; Quinolines; Salmonella typhimurium; SOS Response, Genetics

Mutagenicity, co-mutagenicity and anti-mutagenicity of glycoursodeoxycholic acid (GUDCA) were examined by the Ames assay using Salmonella typhimurium strain TA98 with S9. As pro-mutagens, 2-aminoanthracene (2AA), Benzo[a]pyrene (BaP), 3-amino-1-dimethyl-5H-pyrido[4, 3-b]indole (Trp-P-2), 2-amino-3-methylimidazo[4, 5-f]quinoline (IQ) and 2-amino-3, 4-dimethylimidazo[4, 5-f]quinoline (MeIQ) were used. In addition to these pro-mutagens, blue-chitin extracts of human gallbladder bile (BCE) collected from the cholecystectomized patients with cholelithiasis were used in order to investigate the role of GUDCA on mutagen(s) actually existing in human bile. It was found that GUDCA did not show mutagenicity in this test system. Concerning the modification of mutagenic activities of pro-mutagens, GUDCA showed the different directions. GUDCA acted as co-mutagen, since it enhanced the mutagenic activities of 2AA and BaP. But, acted as anti-mutagen, since it suppressed the activities of Trp-P-2, IQ and MeIQ, all of which were classified as heterocyclic amines. GUDCA also suppressed the mutagen(s) in human bile. Because of the use of blue-chitin absorbed method for testing bile mutagenicity, the chemicals involved were considered to be heterocyclic amines and other polycyclic compounds. In these we suspect the bile mutagens are heterocyclic amines. Further examination should be directed towards the investigation into the mechanism of anti-mutagenic effects of GUDCA on mutagen(s) actually existing in human bile.

Topics: Anthracenes; Antimutagenic Agents; Benzo(a)pyrene; Bile; Carbolines; Humans; Mutagenicity Tests; Mutagens; Quinolines; Salmonella typhimurium; Ursodeoxycholic Acid

The in vivo genotoxicity of five heterocyclic amines-Trp-P-2 (13 mg/kg), IQ (13 mg/kg), MeIQ (13 mg/kg), MeIQx (13 mg/kg), and PhIP (40 mg/kg)-in the mucosa of gastrointestinal and urinary tract organs (stomach, duodenum, jejunum, ileum, colon, and bladder) was studied by the alkaline single cell gel electrophoresis (SCG) (Comet) assay. Male CD-1 mice were sacrificed 1, 3, and 8 h after intraperitoneal injection. All the heterocyclic amines studied yielded statistically significant DNA damage in the colon but not the small intestine (duodenum, jejunum, and ileum) or urinary bladder. In this study, five heterocyclic amines were injected intraperitoneally to avoid the consequences of ingestion. Thus, the extensive damage to colon DNA was concluded to be due, at least in part, to a systemic effect.

Topics: Amines; Animals; Carbolines; Colon; Electrophoresis, Agar Gel; Gastric Mucosa; Imidazoles; Intestinal Mucosa; Male; Mice; Mutagenicity Tests; Mutagens; Quinolines; Urinary Bladder

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

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

Lactic acid bacteria have been reported to have antimutagenic/anticarcinogenic properties in vitro and in vivo. One possible mechanism for this effect involves a physical binding of the mutagenic compounds to the bacteria. The purpose of the present investigation was to study the binding capacity of eight human intestinal or lactic acid bacterial strains for mutagenic heterocyclic amines formed during cooking of protein-rich food. Binding of the mutagens Trp-P-2, PhIP, IQ and MeIQx by the bacterial strains was analyzed by HPLC. There were only minor differences in the binding capacities of the tested strains but the mutagenic compounds were bound with markedly different efficiencies. Trp-P-2 was almost completely bound and the binding tended not to be of a reversible nature. The binding of PhIP, which reached about 50%, was important as PhIP is a major mutagen in the western diet. IQ and MeIQx were slightly less well bound. pH appeared to be of importance for the binding efficacy. Binding correlated well with the reduction in mutagenicity observed after exposure of the heterocyclic amines to the bacterial strains. The results indicate that cooked food mutagenic compounds, commonly found in the western meat-rich diet, can be bound to bacteria from the normal intestinal microflora in vitro.

Topics: Amines; Bifidobacterium; Biotransformation; Carbolines; Chromatography, High Pressure Liquid; Cooking; Food Contamination; Heterocyclic Compounds; Hot Temperature; Hydrogen-Ion Concentration; Imidazoles; Intestines; Lactobacillus; Meat; Mutagenicity Tests; Mutagens; Quinolines; Regression Analysis

The heterocyclic amines (HA) 2-aminodipyrido[1,2-a:3',2-d]imidazole (Glu-P-2), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were mutagenic in V79 cells (Chinese hamster lung fibroblasts) using 6-thioguanine resistance as the marker of mutagenicity. Pancreas duct epithelial cells (DEC) from untreated hamsters, homogenates of pancreas ducts from untreated hamsters and those fed a high fat diet and human DEC were used to activate the heterocyclic amines. When hamster cells and tissues were used the optimum mutation frequencies (mutants/10(6) survivors) measured were: Glu-P-2, 10 +/- 1; MeIQ, 28 +/- 2 (DEC), 12 +/- 2 (control, duct homogenate), and 21 +/- 2 (high fat diet fed, duct homogenate); PhIP, 61 +/- 5. When human DEC were used the optimum mutation frequencies were: MeIQ, 32 +/- 4; PhIP, 35 +/- 3. 3,8-Dimethylimidazo[4,5-f]quinoxaline, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole were not mutagenic in this assay.

Topics: Adolescent; Adult; Amines; Animals; Carbolines; Cells, Cultured; Cricetinae; Heterocyclic Compounds; Humans; Imidazoles; Lung; Male; Mutagens; Pancreatic Ducts; Quinolines

Two slightly different protocols, the plate incorporation method and the preincubation method, are used in the Ames Salmonella mutagen test. Using a preincubation method, we recently demonstrated efficient activation of a number of food-derived promutagens by extracts of mammalian cells expressing cDNAs of rat-liver cytochrome P450IA2 and of a P450IA2-IA1 hybrid. We report here that, for 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 1-aminoanthracene and several other promutagens, preincubation dramatically increased the number of revertant colonies in the Ames test when extracts of cytochrome P450IA2-containing transfected cells or low concentrations of rat-liver extracts were used as the source of activating enzymes. At higher concentrations of rat-liver extract protein, the effect of preincubation was less pronounced. The effect of preincubation was not due to the low protein concentrations in the assays since increasing the total protein concentration did not abolish the requirement for preincubation for the detection of MeIQ activation at low concentrations of rat-liver extract. In experiments where P450IA2 synthesized in transfected cells in culture is used to study promutagen activation, the plate incorporation protocol may seriously underestimate the capacity of cell extracts to activate promutagens. Thus, interlaboratory comparisons become difficult and unnecessarily large quantities of cell extract protein may be needed to detect promutagen activation. Whenever Ames test assays are carried out under conditions where P450 concentration limits revertant yield, it would be prudent to examine both the preincubation and plate incorporation protocol.

Topics: Aflatoxin B1; Anthracenes; Carbolines; Cytochrome P-450 CYP1A2; Cytochrome P-450 Enzyme System; Dihydroxydihydrobenzopyrenes; Dose-Response Relationship, Drug; Fluorenes; Humans; Imidazoles; Liver Extracts; Mutagenesis; Mutagenicity Tests; Mutagens; Oxidoreductases; Quinolines; Salmonella typhimurium; Transfection

The fried food mutagens IQ, MeIQ, Glu-P-1 and Trp-P-2 were treated with nitrite at pH 3.0 for 1 h at 37 degrees C. The resulting reaction mixtures were tested for mutagenicity towards Salmonella typhimurium TA97, TA98, TA100 and TA1535. Glu-P-1 and Trp-P-2 were readily converted to weak or non-mutagenic deaminated compounds, whereas IQ and MeIQ were converted to extremely strong mutagenic derivatives in both the presence and the absence of rat liver S9 mix. The mutagenicity of MeIQ in TA98 was enhanced by nitrite up to 3-fold, while that of nitrosated MeIQ was further enhanced by S9 mix up to 15-fold. The nitrosation products of MeIQ were resolved into 7 bands by TLC on silica gel plate. Bands I, III, V and VI were highly mutagenic to both TA98 and TA100. The experimental results suggest that the non-enzymatic formation of direct-acting mutagens from indirect-acting mutagens such as IQ or MeIQ might be physiologically important, especially with regard to the etiology of human gastrointestinal tract tumors.

Topics: Amines; Carbolines; Chromatography, Thin Layer; Drug Interactions; Imidazoles; Mutagenicity Tests; Mutagens; Nitrites; Nitrosation; Quinolines

The binding of mutagenic pyrolyzates to cell fractions from some gram-negative intestinal bacteria and to thermally treated bacterial cells was investigated. 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) were effectively bound by several of the bacterial cells. The cell wall skeletons of all bacteria effectively bound Trp-P-1 and Trp-P-2. Their cytoplasmic fractions retained Trp-P-1 and Trp-P-2, but to a lesser extent than the cell wall skeletons. 2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) was not found in their cytoplasmic fractions. These cell wall skeletons also bound 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1), 2-amino-5-phenylpyridine (Phe-P-1), IQ, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQX). The amount of each mutagen bound differed with the type of mutagen and the bacterial strain used. The outer membrane of Escherichia coli IFO 14249 showed binding of about 123.7 micrograms/mg of Trp-P-2, and its cytoplasmic membrane bound 57.14 micrograms/mg. Trp-P-2 bound to the bacterial cells was extracted with ammonia (5%), methanol, and ethanol but not with water.

Topics: Bacteroides fragilis; Carbolines; Cell Wall; Chromatography, High Pressure Liquid; Citrobacter freundii; Escherichia coli; Gram-Negative Bacteria; Hot Temperature; Imidazoles; Mutagens; Pseudomonas putida; Quinolines

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

Female BALB/c mice were fed a low fat diet (1% safflower oil, by weight) or one supplemented with 25% (by weight) of beef fat or olive oil. The abilities of these diets to modify the in vitro and in vivo hepatic conversion of the dietary carcinogens aflatoxin B1, 2-amino-3, 4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) to bacterial mutagens was evaluated. Dietary olive oil appeared to increase the metabolism of both MeIQ and Trp-P-2 to bacterial mutagens in vivo using the intrasanguineous host-mediated assay. Feeding mice either of the high-fat diets increased hepatic conversion of these two compounds to bacterial mutagens in vitro. Dietary fat had no effect on the metabolism of aflatoxin B1. Subsequent experiments suggested that the in vivo effects of dietary olive oil on MeIQ and Trp-P-2 mutagenesis were due to the induction of hepatic enzyme activities rather than to increased rates of uptake of the carcinogen from the gut-lumen.

Topics: Aflatoxin B1; Aflatoxins; Animals; Carbolines; Carcinogens; Dietary Fats; Female; Intestine, Small; Liver; Mice; Mice, Inbred BALB C; Mutagenicity Tests; Mutagens; Organ Size; Quinolines

Metabolic activation of the food mutagens 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and aflatoxin B1 by female BALB/c mice of different ages (2-24 weeks) was investigated in vivo and in vitro using Salmonella typhimurium TA98 as the indicator organism. The in vivo activation of the three mutagens was investigated in 4- and 24-week-old mice using an intrasanguineous host-mediated assay. All three compounds showed reduced levels of activation with the older hosts. Hepatic S9 fractions from female mice of varying ages between 2 and 24 weeks were used in the in vitro mutagenicity assay. To achieve optimal activation to bacterial mutagens, 5% S9 was required for aflatoxin B1 and Trp-P-2 and 10% S9 for MeIQ; age of donor generally had little effect on the profile of these protein activation curves. Under these optimal conditions MeIQ and Trp-P-2 both exhibited, as before, age-dependent decreases in activation over a wide range of mutagen concentrations, however the in vitro activation of aflatoxin showed no consistent change with age. Spectrophotometric measurements of S9 cytochrome P-450 content showed a decrease in concentration with increasing age, but this was not sufficient to account for changes observed in hepatic mutagen activation. However, changes in the activities of certain cytochrome P-450 isoenzymes and cytosolic GSH-transferases, which in turn result in changes in the activation and detoxification capacity of the liver, would appear to explain age-dependent changes in the activity of mutagens in vivo.

Topics: Aflatoxin B1; Aflatoxins; Aging; Animals; Biotransformation; Carbolines; Cytochrome P-450 Enzyme System; Female; Food Contamination; Glutathione Transferase; Liver; Mice; Mice, Inbred BALB C; Mutagenicity Tests; Mutagens; Quinolines

Female BALB/c mice were fed diets containing equimolar amounts of quercetin or its glycoside, rutin, for 5 weeks. These mice were used either in host-mediated bacterial mutation assays or as sources of hepatic microsomes. In host-mediated bacterial mutation assays using radiolabelled mutagens, the heterocyclic amines 2-amino-3,5-dimethyl[4,5-f]imidazoquinoline (MeIQ) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) induced greater numbers of revertants in mice fed either of the flavonoid diets compared with control. Experiments using hepatic microsomes revealed that although feeding mice either flavonoid produced slight changes in some parameters of hepatic xenobiotic metabolism (mixed function oxidase and glutathione transferase activities), microsomes from quercetin-fed mice were more potent activators of both MeIQ and Trp-P-2 compared with microsomes from control or rutin-fed mice. This difference in microsomal ability may be due to the different biological availability of the two flavonoids within the gastrointestinal tract.

Topics: Animals; Carbolines; Diet; DNA Damage; Female; Flavonoids; Kinetics; Mice; Mice, Inbred BALB C; Microsomes, Liver; Mutagenicity Tests; Mutagens; Quercetin; Quinolines; Rutin; Xenobiotics

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

Topics: Administration, Oral; Animals; Carbolines; Colon; Epithelium; Female; Flavonoids; Food Analysis; Mice; Mice, Inbred C57BL; Quercetin; Quinolines; Sister Chromatid Exchange

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