benzofurans and 2-3-7-8-tetrachlorodibenzofuran

In rhesus macaques (Macaca mulatta), consumption of food containing commercial polychlorinated biphenyl (PCB) mixtures, some pure polychlorobiphenyl congeners, 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD), and 2,3,7,8-tetrachlorodibenzofuran (TCDF) caused the same clinical toxic manifestations and histopathologic lesions, although the potencies of the toxicants covered a range of five orders of magnitude. Recovery from poisoning by 3,4,3',4'-tetrachlorobiphenyl (34TCB) or TCDF was rapid, whereas recovery from poisoning by Aroclor 1242, 3,4,5,3', 4', 5'-hexachlorobiphenyl (345HCB) or TCDD was protracted, if it occurred at all. 34TCB did not appreciably accumulate in body fat, but the level of 345HCB in fat rose steadily during ingestion. In one monkey, 25% of TCDD stored in fat after a single dose was still present after 2 years. Among the symmetrical tetra-and hexachlorobiphenyl isomers tested, subacute oral toxicity could be demonstrated only for those without ortho chlorine substitutions. 34TCB and 345HCB were toxic at dietary levels of less than 1 ppm, but ingestion of food containing 2,5,2',5'- tetrachlorobiphenyl at 5 ppm, or 2,4,5,2',4',5'-, 2,4,6,2',4',6'-, or 2,3,6,2',3',6'-hexachlorobiphenyl at 15 or 65 ppm, caused no discernible deleterious effects. The principal demonstrable histopathological lesions, bone marrow excepted, were metaplasias in some specialized epithelial structures, such as sebaceous glands, nail beds, gastric mucosa, ameloblast, and thymic corpuscles. These changes were interpreted as toxicant-induced, reversible redirection of differentiation. This aberration was wholly reversible. TCDD and 34TCB caused abortions when given in one or a few oral doses early in pregnancy. At the total doses used (1 or 5 micrograms/kg of body weight for TCDD, 3 or 0.6 mg/kg of body weight for 34TCB), maternal toxicity was frequently apparent subsequent to the abortion.

Topics: Abortion, Spontaneous; Acne Vulgaris; Animals; Benzofurans; Cell Differentiation; Dioxins; Epithelium; Female; Fetus; Gastric Mucosa; Isomerism; Macaca mulatta; Male; Nails; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Pregnancy; Structure-Activity Relationship

Topics: Animals; Benzofurans; Carcinogens; Chlorophenols; Dibenzofurans, Polychlorinated; Environmental Pollutants; Food Contamination; Guinea Pigs; Herbicides; Hexachlorobenzene; Humans; Mice; Oils; Polychlorinated Biphenyls; Rats; Teratogens; Tissue Distribution

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/DFs) are byproducts of brominated flame retardants and can cause adverse health effects. Although exposure to polychlorinated (PC) DD/DFs induces toxic effects, including liver injury and neurobehavioral disorder, little is known about toxicities associated with PBDD/DF exposure. Thus, we examined effects of perinatal exposure to brominated congener on the infant mouse. Gene expression in several organs, such as the liver and brain, was analyzed in mouse offspring born to dams administered 2,3,7,8-tetrabromodibenzofuran (TBDF; 9 or 45 μg/kg body weight) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 3 μg/kg body weight) on gestational day 12.5. An increase in liver size was observed in TBDF- or TCDD-exposed offspring in infancy. Gene microarray analysis revealed that 163 and 36 genes were markedly upregulated and downregulated, respectively, in the liver of TBDF-exposed mice compared with those in vehicle-treated mice on postnatal day (PND) 5. Significant increases in Cyp1a1, Cyp1a2, Fmo3, and Pnliprp1 and decreases in Tff3, Ocstamp, Kcnk16, and Lgals2 mRNA levels in TBDF-exposed offspring on PNDs 5 and 12 were confirmed by quantitative PCR. In particular, a significant reduction in Tff3 mRNA in the liver, but not in the brain, small intestine, colon, and kidney, was observed in offspring perinatally exposed to TBDF or TCDD. Ultrasonic calls of TBDF- or TCDD-exposed offspring on PNDs 3-5 were impaired. Taken together, perinatal exposure to polyhalogenated dioxin/furan congeners disrupts gene expression patterns in the liver and ultrasonic calling during infancy. These results suggest that liver injury may contribute to neurobehavioral disorder.

Topics: Animals; Benzofurans; Female; Gene Expression; Liver; Male; Mice; Mice, Inbred C57BL; Trefoil Factor-3

Aryl hydrocarbon receptor (AHR) activation via 2,3,7,8-tetrachlorodibenzofuran (TCDF) induces the accumulation of hepatic lipids. Here we report that AHR activation by TCDF (24  μg/kg body weight given orally for five days) induced significant elevation of hepatic lipids including ceramides in mice, was associated with increased expression of key ceramide biosynthetic genes, and increased activity of their respective enzymes. Results from chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA) and cell-based reporter luciferase assays indicated that AHR directly activated the serine palmitoyltransferase long chain base subunit 2 (Sptlc2, encodes serine palmitoyltransferase 2 (SPT2)) gene whose product catalyzes the initial rate-limiting step in de novo sphingolipid biosynthesis. Hepatic ceramide accumulation was further confirmed by mass spectrometry-based lipidomics. Taken together, our results revealed that AHR activation results in the up-regulation of Sptlc2, leading to ceramide accumulation, thus promoting lipogenesis, which can induce hepatic lipid accumulation.

Topics: Activation, Metabolic; Animals; Basic Helix-Loop-Helix Transcription Factors; Benzofurans; Ceramides; Gene Expression Regulation; Humans; Lipidomics; Lipogenesis; Liver; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Receptors, Aryl Hydrocarbon; Serine C-Palmitoyltransferase; Sphingomyelin Phosphodiesterase; Triglycerides

Environmental exposure to 2,3,7,8-tetrachlorodibenzofuran (TCDF), one of typical persistent organic pollutants (POPs) produced from municipal waste combustion, exerts toxic effects on human healthy. In the current study, we mainly used targeted metabolomics combined with untargeted

Topics: Animals; Benzofurans; Fatty Liver; Humans; Liver; Male; Metabolomics; Mice; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease

Fetal rat exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) reduces epididymal sperm number involving altered pituitary-testicular hormonal signaling as the proposed mode-of-action (MOA). To evaluate this MOA and compare TCDD to 2,3,7,8-tetrachlorodibenzofuran (TCDF), an in utero rat exposure and study was conducted. Endpoints included congener tissue levels and transcriptomes of maternal liver and fetal liver, testis, and pituitary. Decreased gonadotropin subunit mRNAs levels (Lhb and Fshb) and enriched signaling pathways including GNRH Signaling and Calcium Signaling were observed in fetal pituitary after TCDD (but not TCDF) exposure. TCDD (but not TCDF) decreased fetal testis cholesterologenic and steroidogenic pathway genes. TCDD tissue concentrations in dam liver, dam adipose, and whole fetus were approximately 3- to 6-fold higher than TCDF. These results support a MOA for dioxin-induced rat male reproductive toxicity involving key events in both the fetal pituitary (e.g., reduced gonadotropin production) and fetal testis (e.g., reduced Leydig cell cholesterologenesis and steroidogenesis).

Topics: Animals; Benzofurans; Female; Fetus; Gene Expression Profiling; Gene Expression Regulation, Developmental; Liver; Male; Pituitary Gland; Polychlorinated Dibenzodioxins; Pregnancy; Rats, Sprague-Dawley; Testis

Emerging evidence supports that exposure to persistent organic pollutants (POPs) can impact the interaction between the gut microbiota and host. Recent efforts have characterized the relationship between gut microbiota and environment pollutants suggesting additional research is needed to understand potential new avenues for toxicity. Here, we systematically examined the direct effects of POPs including 2,3,7,8-tetrachlorodibenzofuran (TCDF), 2,3,7,8-tetrachlorodibenzo-

Topics: Animals; Bacteria; Benzofurans; Carbon; Cecum; Citric Acid Cycle; Gastrointestinal Microbiome; Lipid Metabolism; Male; Mice; Mice, Inbred C57BL; Persistent Organic Pollutants; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Protein Transport; Pyruvic Acid

Toxic potencies of xenobiotics such as halogenated aromatic hydrocarbons inducing 2,3,7,8-tetrachlorodibenzo-p-dioxin/2,3,7,8-tetrachlorodibenzofuran (TCDD/TCDF)-like effects were investigated by quantitative structure-toxicity relationships (QSTR) using their aryl hydrocarbon receptor (AhR) binding affinity data. A descriptor pool was created using the SPARTAN 10, DRAGON 6.0 and ADMET 8.0 software packages, and the descriptors were selected using QSARINS (v.2.2.1) software. The QSTR models generated for AhR binding affinities of chemicals with TCDD/TCDF-like effects were internally and externally validated in line with the Organization of Economic Co-operation and Development (OECD) principles. The TCDD-based model had six descriptors from DRAGON 6.0 and ADMET 8.0, whereas the TCDF-based model had seven descriptors from DRAGON 6.0. The predictive ability of the generated models was tested on a diverse group of chemicals including polychlorinated/brominated biphenyls, dioxins/furans, ethers, polyaromatic hydrocarbons with fused heterocyclic rings (i.e. phenoxathiins, thianthrenes and dibenzothiophenes) and polyaromatic hydrocarbons (i.e. halogenated naphthalenes and phenanthrenes) with no AhR binding data. For the external set chemicals, the structural coverage of the generated models was 90% and 89% for TCDD and TCDF-like effects, respectively.

Topics: Animals; Benzofurans; Hepatocytes; Models, Molecular; Polychlorinated Dibenzodioxins; Quantitative Structure-Activity Relationship; Rats; Receptors, Aryl Hydrocarbon; Xenobiotics

This study aimed to investigate the toxic impact prompted in the testes of adult mice exposed to 2,3,7,8-tetrachlorodibenzofuran (TCDF). Four groups of 12 mice each were used in the present study. Group 1 mice were kept as control and administered corn oil only. Group 2 animals were given glutathione (GSH) in a dose of 100 mg/kg body weight by oral gavage twice a week. Group 3 was given TCDF orally twice per week, in a dose of 0.5 μg/kg body weight for 8 weeks. Group 4 was administered GSH orally in a dosage of 100 mg/kg body weight plus TCDF twice a week for 8 weeks. Animals were sacrificed after 2, 4, and 8 weeks of exposure, serum samples were collected for estimation of testosterone hormone, the testes were dissected and one part was used for estimation of superoxide dismutase (SOD), malondialdehyde (MDA), lactate dehydrogenase (LDH), and 3β-hydroxysteroid dehydrogenase. Another portion of the testis was kept in formalin for histopathological examination. The results showed that the activities of SOD were decreased while the levels of lipid peroxidation MDA were increased in the testicular tissues of the exposed mice. The serum testosterone level and the steroidogenic enzyme 3β-hydroxysteroid dehydrogenase activity of testicular homogenate were essentially decreased in TCDF-treated mice. A significant increment in the testicular LDH activity in testicular tissues was recorded in mice exposed to TCDF. The percentage of DNA chromatin disintegration was significantly increased in TCDF-treated mice. Histopathological changes were recorded in TCDF-exposed group as degenerative changes of the seminiferous tubules with formation of spermatid giant cells at 2 weeks in addition to exhaustion of germinal epithelium and detachment of the germ cells from the basal lamina at 4 and 8 weeks. Co-administration of GSH could reestablish MDA and LDH levels besides reduction in percentage of sperm DNA damage and improvement of the testicular tissue architecture.

Topics: 17-Hydroxysteroid Dehydrogenases; Animals; Benzofurans; DNA; Glutathione; L-Lactate Dehydrogenase; Lipid Peroxidation; Male; Malondialdehyde; Mice; Oxidative Stress; Sperm Count; Spermatozoa; Superoxide Dismutase; Testis; Testosterone

To explore the potential reactivity of the methylidyne radical (CH) toward 2,3,7,8-tetrachlorodibenzo-

Topics: Benzofurans; Cyclization; Density Functional Theory; Kinetics; Molecular Dynamics Simulation; Polychlorinated Dibenzodioxins; Thermodynamics

The current environmental legislations recommend monitoring chemical contaminants such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans before the use of sewage sludge on the agricultural land. In this study, a solid-liquid extraction with low-temperature purification (SLE-LTP) was optimized and validated to determine 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran in sewage sludge and soil samples. The analyses were performed by gas chromatography-mass spectrometry operating in the selective ion mode (GC-MS-SIM). Acetonitrile:ethyl acetate 6.5:1.5 (v/v) was the best extraction phase, and the recoveries percentages were close to 100%. The linearity was demonstrated in the range of 1.25-25 µg L

Topics: Acetonitriles; Agriculture; Benzofurans; Brazil; Chemical Fractionation; Cities; Dibenzofurans, Polychlorinated; Environmental Monitoring; Gas Chromatography-Mass Spectrometry; Limit of Detection; Polychlorinated Dibenzodioxins; Sewage; Soil Pollutants

Dioxins and dioxin-like compounds (DLCs) are potent toxicants to most vertebrates. Sensitivities to DLCs vary among species. In the present study, the sensitivities of avian species (chicken [Gallus gallus], ring-necked pheasant [Phasianus colchicus], and Japanese quail [Coturnix japonica]) to some polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were determined by using species-specific, in vitro, transactivation assays based on a luciferase reporter gene under control of species-specific aryl hydrocarbon receptors. In ring-necked pheasant and Japanese quail, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was not the most potent inducer of toxic effects. Especially for Japanese quail, the relative potency values of most of 9 PCDD/Fs tested were greater than for TCDD. The rank order of avian species sensitivities to DLCs was chicken > ring-necked pheasant > Japanese quail. Effects of binary mixtures of TCDD, 2,3,7,8-tetrachlorodibenzofuran, and 2,3,4,7,8-pentachlorodibenzofuran were strictly additive. Moreover, we also found that the primary DLCs that were responsible for most of the potency of the DLC mixtures can be deduced by using ordination in a multidimensional space defined by the avian species sensitivities. Overall, the relative potency and the species sensitivities of these chemicals could guide risk assessments to wild species when exposure to mixtures of DLCs in the environment.

Topics: Animals; Benzofurans; Chickens; Coturnix; Dioxins; Dioxins and Dioxin-like Compounds; Galliformes; Genes, Reporter; Luciferases; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Species Specificity; Transcriptional Activation

Obesity, a risk factor for developing metabolic complications, is a major public health problem. Abdominal obesity is strongly accompanied by a cluster of metabolic abnormalities characterized by insulin resistance. The link between persistent organic pollutants (POPs) and insulin resistance has been investigated in animal and epidemiological studies. We aimed to examine whether insulin resistance is greater in people with abdominal obesity (AO) and concomitant exposure to serum dioxins (PCDD/Fs). We conducted a cross-sectional descriptive study of 2876 participants living near a PCDD/Fs contaminated area. Seventeen 2,3,7,8-substituted PCDD/Fs congeners were measured, and then the associations between the main predictor variable, serum TEQDF-1998, abdominal obesity (AO), dependent variables, and insulin resistance were examined. Twelve of the 17 congeners, widely distributed among PCDDs, and PCDFs, had trends for associations with abdominal adiposity. In men, the highest quintiles of 1,2,3,7,8-PeCDF; 1,2,3,7,8-PeCDD; 2,3,7,8-TCDD; 2,3,7,8-TCDF; and 2,3,4,7,8-PeCDF had the top five adjusted odds ratios (AORs) + 95% confidence intervals (CIs):[4.2; 2.7-6.4], [3.6; 2.3-5.7], [3.2; 2.1-5.0], [3.0; 2.0-4.5], and [2.9; 1.9-4.7], respectively. In women, the highest quintiles of 1,2,3,4,7,8,9-HpCDF; 1,2,3,6,7,8-HxCDF; and 1,2,3,4,6,7,8-HpCDF had the top three AORs + 95% CIs:[3.0; 1.9-4.7], [2.0; 1.3-3.1], and [1.9; 1.3-2.9], respectively. After confounding factors had been adjusted for, men, but not women, with higher serum TEQDF-1998 levels or abdominal obesity had a significantly (Ptrend < 0.001) greater risk for abnormal insulin resistance. The groups with the highest joint serum TEQDF-1998 and abdominal obesity levels were associated with elevated insulin resistance at 5.0 times the odds of the groups with the lowest joint levels (AOR 5.23; 95% CI: 3.53-7.77). We hypothesize that serum TEQDF-1998 and abdominal obesity affect the association with insulin resistance in general populations.

Topics: Adult; Benzofurans; Cross-Sectional Studies; Environmental Exposure; Environmental Pollutants; Female; Humans; Insulin Resistance; Male; Middle Aged; Obesity, Abdominal; Polychlorinated Dibenzodioxins; Sex Factors

Alteration of the gut microbiota through diet and environmental contaminants may disturb physiological homeostasis, leading to various diseases including obesity and type 2 diabetes. Because most exposure to environmentally persistent organic pollutants (POPs) occurs through the diet, the host gastrointestinal tract and commensal gut microbiota are likely to be exposed to POPs.. We examined the effect of 2,3,7,8-tetrachlorodibenzofuran (TCDF), a persistent environmental contaminant, on gut microbiota and host metabolism, and we examined correlations between gut microbiota composition and signaling pathways.. Six-week-old male wild-type and Ahr-/- mice on the C57BL/6J background were treated with 24 μg/kg TCDF in the diet for 5 days. We used 16S rRNA gene sequencing, 1H nuclear magnetic resonance (NMR) metabolomics, targeted ultra-performance liquid chromatography coupled with triplequadrupole mass spectrometry, and biochemical assays to determine the microbiota compositions and the physiological and metabolic effects of TCDF.. Dietary TCDF altered the gut microbiota by shifting the ratio of Firmicutes to Bacteroidetes. TCDF-treated mouse cecal contents were enriched with Butyrivibrio spp. but depleted in Oscillobacter spp. compared with vehicle-treated mice. These changes in the gut microbiota were associated with altered bile acid metabolism. Further, dietary TCDF inhibited the farnesoid X receptor (FXR) signaling pathway, triggered significant inflammation and host metabolic disorders as a result of activation of bacterial fermentation, and altered hepatic lipogenesis, gluconeogenesis, and glycogenolysis in an AHR-dependent manner.. These findings provide new insights into the biochemical consequences of TCDF exposure involving the alteration of the gut microbiota, modulation of nuclear receptor signaling, and disruption of host metabolism.

Topics: Animals; Benzofurans; Bile Acids and Salts; Diet; Environmental Pollutants; Gastrointestinal Microbiome; Gastrointestinal Tract; Homeostasis; Liver; Male; Metabolomics; Mice, Inbred C57BL; Mice, Knockout; Microbiota; Receptors, Aryl Hydrocarbon; Receptors, Cytoplasmic and Nuclear; RNA, Ribosomal, 16S; Signal Transduction

Environmental exposure to dioxins and dioxin-like compounds poses a significant health risk for human health. Developing a better understanding of the mechanisms of toxicity through activation of the aryl hydrocarbon receptor (AHR) is likely to improve the reliability of risk assessment. In this study, the AHR-dependent metabolic response of mice exposed to 2,3,7,8-tetrachlorodibenzofuran (TCDF) was assessed using global (1)H nuclear magnetic resonance (NMR)-based metabolomics and targeted metabolite profiling of extracts obtained from serum and liver. (1)H NMR analyses revealed that TCDF exposure suppressed gluconeogenesis and glycogenolysis, stimulated lipogenesis, and triggered inflammatory gene expression in an Ahr-dependent manner. Targeted analyses using gas chromatography coupled with mass spectrometry showed TCDF treatment altered the ratio of unsaturated/saturated fatty acids. Consistent with this observation, an increase in hepatic expression of stearoyl coenzyme A desaturase 1 was observed. In addition, TCDF exposure resulted in inhibition of de novo fatty acid biosynthesis manifested by down-regulation of acetyl-CoA, malonyl-CoA, and palmitoyl-CoA metabolites and related mRNA levels. In contrast, no significant changes in the levels of glucose and lipid were observed in serum and liver obtained from Ahr-null mice following TCDF treatment, thus strongly supporting the important role of the AHR in mediating the metabolic effects seen following TCDF exposure.

Topics: Animals; Benzofurans; Dioxins; Environmental Pollutants; Fatty Acids; Gene Expression; Glucose; Lipid Metabolism; Liver; Magnetic Resonance Spectroscopy; Male; Metabolomics; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Receptors, Aryl Hydrocarbon

Two interference peaks which generally appeared in company with 13C labeled 2,3,7,8-tetrachlorodibenzofuran (13C12-2,3,7,8-TCDF) in the same ion channel during dioxin analysis for biological samples were identified using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) and high resolution gas chromatography/low resolution mass spectrometry (HRGC/LRMS). It was firstly inferred that the interference peaks should be the two isomers of dichlorodiphenyldichloroethylene (DDE), which was a breakdown product of dichlorodiphenyltrichloroethane (DDT), one of the typical organic chlorine pesticides (OCPs). Thereafter, the standard solution of DDE including o,p'-DDE and p,p'-DDE was analyzed for confirmation. By evaluation of the peak separation in HRGC/HRMS, comparison of the GC retention times and ion abundance ratios of the two interference peaks in real samples with the two DDE isomers in standard solution, the interference peaks were finally confirmed as o,p'-DDE and p,p'-DDE in sequence on a DB-5MS column. This study provided valuable information for accurate identification of dioxin compounds during the biological sample analysis.

Topics: Benzofurans; DDT; Dioxins; Gas Chromatography-Mass Spectrometry; Hydrocarbons, Chlorinated; Mitotane; Pesticides; Polychlorinated Dibenzodioxins

Novel methods that predict the sensitivity of avian embryos to the toxic effects of dioxin-like compounds (DLCs) using either (1) knowledge of the identity of amino acids at key sites within the ligand binding domain of aryl hydrocarbon receptor 1 (AHR1) or (2) a luciferase reporter gene assay that measures AHR1 activation were recently reported. Results from both methods predict that European starling (Sturnus vulgaris) and domestic chicken (Gallus gallus domesticus) embryos have similar sensitivity to the biochemical and toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) and 2,3,7,8-tetrachlorodibenzofuran (TCDF). Chicken embryos are highly sensitive to DLC toxicity, and the prediction that starlings are equally sensitive is surprising given their widespread distribution and large population size. In an attempt to learn more about starling sensitivity to DLCs, we determined concentration-dependent effects of TCDD, PeCDF and TCDF on cytochrome P4501A4 and 1A5 (CYP1A4 and 1A5) mRNA levels in primary cultures of hepatocytes prepared from embryonic European starlings. It has been demonstrated that the sensitivity of avian hepatocytes to CYP1A4/5 induction is well correlated with LD50 values of DLCs for several avian species. The results of the present study indicate that European starling hepatocytes are indeed as sensitive as chicken hepatocytes to CYP1A4/5 induction after exposure to TCDD. However, starling hepatocytes are less sensitive than chicken hepatocytes to CYP1A4/5 induction by PeCDF and TCDF.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Avian Proteins; Benzofurans; Cell Survival; Cells, Cultured; Chick Embryo; Chickens; Genes, Reporter; Hepatocytes; Lethal Dose 50; Luciferases; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Risk Assessment; RNA, Messenger; Starlings

Catalytic diesel particle filters (DPFs) have evolved to a powerful environmental technology. Several metal-based, fuel soluble catalysts, so-called fuel-borne catalysts (FBCs), were developed to catalyze soot combustion and support filter regeneration. Mainly iron- and cerium-based FBCs have been commercialized for passenger cars and heavy-duty vehicle applications. We investigated a new iron/potassium-based FBC used in combination with an uncoated silicon carbide filter and report effects on emissions of polychlorinated dibenzodioxins/furans (PCDD/Fs). The PCDD/F formation potential was assessed under best and worst case conditions, as required for filter approval under the VERT protocol. TEQ-weighted PCDD/F emissions remained low when using the Fe/K catalyst (37/7.5 μg/g) with the filter and commercial, low-sulfur fuel. The addition of chlorine (10 μg/g) immediately led to an intense PCDD/F formation in the Fe/K-DPF. TEQ-based emissions increased 51-fold from engine-out levels of 95 to 4800 pg I-TEQ/L after the DPF. Emissions of 2,3,7,8-TCDD, the most toxic congener (TEF = 1.0), increased 320-fold, those of 2,3,7,8-TCDF (TEF = 0.1) even 540-fold. Remarkable pattern changes were noticed, indicating a preferential formation of tetrachlorinated dibenzofurans. It has been shown that potassium acts as a structural promoter inducing the formation of magnetite (Fe3O4) rather than hematite (Fe2O3). This may alter the catalytic properties of iron. But the chemical nature of this new catalyst is yet unknown, and we are far from an established mechanism for this new pathway to PCDD/Fs. In conclusion, the iron/potassium-catalyzed DPF has a high PCDD/F formation potential, similar to the ones of copper-catalyzed filters, the latter are prohibited by Swiss legislation.

Topics: Benzofurans; Catalysis; Filtration; Iron; Polychlorinated Dibenzodioxins; Potassium

This study assessed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 2,3,7,8-tetrachlorodibenzofuran (TCDF) on the reproductive performance of female mink (Mustela vison) and the viability and growth of their offspring. Nine adult female mink were randomly assigned to one of 13 dietary treatments (one control and four doses each of TCDD, PeCDF, and TCDF [2.1-8.4, 4.0-15 and 5.2-25 ng TCDD toxic equivalents (TEQ)/kg body wt/d]). Diets were fed from two months prior to breeding through weaning of offspring at six weeks of age. At least nine kits per treatment group were maintained on their diets through 27 weeks of age. There were no effects on litter size or viability of offspring. No consistent effects were observed on body mass or relative organ masses of animals at any age. 2,3,7,8-Tetrachlorodibenzo-p-dioxin and PeCDF accumulated in the liver and adipose tissue, but TCDF cleared rapidly. The lack of significant effects on reproduction and offspring viability contrasts with effects reported for mink exposed to environmentally derived PCB mixtures with equivalent TCDD potencies. This suggests that it may be inappropriate to apply toxicity reference values associated with PCB mixtures to animals also exposed to TCDD, PeCDF, or TCDF, and the World Health Organization TCDD toxic equivalency factors for some congeners may not be appropriate for mink.

Topics: Adult; Animals; Benzofurans; Diet; Environmental Pollutants; Female; Humans; Litter Size; Liver; Male; Mink; Organ Size; Polychlorinated Biphenyls; Random Allocation; Reproduction

High-accuracy molecular orbital calculation has been performed to investigate the atmospheric oxidation reaction of 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TeCDF) initiated by the OH radical in the presence of O(2) and NO/H(2)O. The possible channels involved in the reaction are discussed, and the favorable reaction pathways are revealed. The degradation occurs easily once the OH radical initiates the reaction. Two aspects need to be mentioned: one is that H(2)O in atmosphere is a source of OH radical which will initiate a new round of degradation and improve the degradation efficiency; the other is that the furan ring of 2,3,7,8-TeCDF can be turned into dioxin ring, which may explain the experimental hypothesis that polychlorodibenzofurans can be transformed to polychlorodibenzo-p-dioxins. Rate constants of the elementary reactions are calculated over a temperature range of 250-400K. Arrhenius formulas are fitted and the atmospheric lifetimes of reaction species in the troposphere are discussed for the first time, which can be applied to the study on the model simulation and the management of the hazardous materials.

Topics: Air Pollutants; Atmosphere; Benzofurans; Computer Simulation; Dioxins; Furans; Hydroxyl Radical; Kinetics; Models, Chemical; Nitric Oxide; Oxidation-Reduction; Oxygen; Polychlorinated Dibenzodioxins; Water

This study assessed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 2,3,7,8 tetrachlorodibenzofuran (TCDF) on the incidence of jaw lesions and on hepatic cytochrome P4501A (CYP1A) endpoints in mink (Mustela vison). Adult female mink were assigned randomly to one of 13 dietary treatments (control and four increasing doses of TCDD, PeCDF, or TCDF) and provided spiked feed for approximately 150 d (60 d prior to breeding through weaning of offspring at 42 d post-parturition). Offspring were maintained on their respective diets for an additional 150 d. Activity of hepatic CYP1A enzymes in adult and juvenile mink exposed to TCDD, PeCDF, or TCDD was generally greater compared with controls, but changes in other CYP1A endpoints were less consistent. Histopathology of the mandible and maxilla of juvenile mink suggested a dose-related increase in the incidence of jaw lesions. The dietary effective doses (ED) for jaw lesions in 50% of the population (ED50) were estimated to be 6.6, 14, and 149 ng/kg body weight (bw)/d for TCDD, PeCDF, and TCDF, respectively. The relative potencies of PeCDF and TCDF compared with TCDD based on ED10, ED20, and ED50 values ranged from 0.5 to 1.9 and 0.04 to 0.09, respectively. These values are within an order of magnitude of the World Health Organization toxic equivalency factor (TEF(WHO)) values of 0.3 and 0.1 for PeCDF and TCDF, respectively.

Topics: Animals; Benzofurans; Cytochrome P-450 CYP1A1; Diet; Endpoint Determination; Female; Gene Expression; Incidence; Jaw; Liver; Male; Mink; Polychlorinated Dibenzodioxins; Toxicity Tests, Chronic

In order to find out the characteristics of dioxin contamination, we sampled and analyzed the soil and groundwater on a chlor-alkali factory site that uses graphite anode for production. The results show that the toxic equivalent quantity (TEQ) of dioxins in soil samples exceeds the U. S. EPA region screening value (RSL), with the chlorine hydrogen processing workshop, the electric tank workshop, the asbestos stack area, the sewage treatment plant and the oil depot were affected. The dioxin concentration limit of the groundwater sample doesn't exceed the drinking water standard of China. Considering the fingerprints characteristics of dioxin-contaminated concentration, dioxin isomers content and TEQ, the priority pollutants for control on this site are 2,3,7,8-TCDF, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, OCDD and 2,3,7,8-TCDD. The results show that dioxin pollution is very serious in the chlor-alkali plant that uses graphite anode for production, and the environmental supervision is imperative.

Topics: Alkalies; Benzofurans; Chemical Industry; China; Dioxins; Electrodes; Environmental Pollutants; Graphite; Soil Pollutants

Egg injection studies were performed to confirm a proposed model of relative sensitivity of birds to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this model, species are classified as belonging to one of three categories of sensitivity based on amino acid substitutions in the ligand-binding domain of the aryl hydrocarbon receptor. Embryo lethality and relative potencies of 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) were compared with TCDD for Japanese quail (Coturnix japonica; least sensitive), Common pheasant (Phasianus colchicus; moderately sensitive), and White Leghorn chicken (Gallus gallus domesticus; most sensitive). Doses ranging from 0.044 to 37 pmol/g egg (0.015-12 ng/g egg) were injected into the air cell of eggs prior to incubation. LD(50) (95% confidence intervals) values, based on rate of hatching for TCDD, PeCDF, and TCDF, were 30 (25-36), 4.9 (2.3-9.2), and 15 (11-24) pmol/g egg for the quail, 3.5 (2.3-6.3), 0.61 (0.28-1.2), and 1.2 (0.62-2.2) pmol/g egg for pheasant, and 0.66 (0.47-0.90), 0.75 (0.64-0.87), and 0.33 (0.23-0.45) pmol/g egg for chicken, respectively. LD(50)-based relative potencies of PeCDF and TCDF were 6.1 and 2.0 for quail, 5.7 and 2.9 for pheasant, and 0.88 and 2.0 for chicken, respectively. TCDD was not the most potent compound among the species tested, with PeCDF and TCDF being more potent than TCDD in the quail and pheasant. TCDF was the most potent in chicken. Species sensitivity was as expected for TCDD and TCDF, whereas for PeCDF, the chicken and pheasant were similar in sensitivity and both were more sensitive than the quail. Results from companion in vitro studies are generally similar to those reported here with a few exceptions.

Topics: Animals; Benzofurans; Chick Embryo; Chickens; Coturnix; Embryo, Nonmammalian; Galliformes; Lethal Dose 50; Models, Biological; Ovum; Polychlorinated Dibenzodioxins; Species Specificity; Toxicity Tests

Liver of blue shark (Prionace glauca) specimens from the South-Eastern Mediterranean Sea were analyzed for the presence of polychlorinated biphenyls (PCBs), including coplanar congeners, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). PCBs were the dominant chemicals, followed by PCDFs and PCDDs. The pattern of PCB congener concentrations in the hepatic tissue was dominated by higher chlorinated compounds. The specific profile of toxic PCDD/F congeners was characterized mainly by 2,3,7,8-TCDF and 2,3,7,8-TCDD, followed by 1,2,3,6,7,8-HxCDD and 2,3,4,6,7,8-HxCDF. The total 2,3,7,8-TCDD toxic equivalent (TEQs) was 149 pg g⁻¹ lipid wt. The profile of TEQ shows that PCDDs present the greatest risk to this species contributing to total toxicity with a percentage approximately of 60%, while the contribution of PCDFs and DL-PCBs is almost the same being 22.4% and 21.6%, respectively. Further investigations are urgently needed to characterize the PCDD/Fs contamination levels not only in elasmobranch fish but in all Mediterranean marine biota.

Topics: Animals; Benzofurans; Dibenzofurans, Polychlorinated; Environmental Monitoring; Italy; Liver; Mediterranean Sea; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Sharks; Water Pollutants, Chemical

To evaluate the sensitivity and responses to dioxins and related compounds (DRCs) via aryl hydrocarbon receptor (AHR) in Baikal seals (Pusa sibirica), we constructed an in vitro reporter gene assay system. Baikal seal AHR (BS AHR) expression plasmid and a reporter plasmid containing CYP1A1 promoter were transfected in COS-7 cells. The cells were treated with six representative congeners, and dose-dependent responses were obtained for all the congeners. EC50 values of 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,7,8-TCDF, 2,3,4,7,8-PeCDF, and PCB126 were found to be 0.021, 1.8, 0.16, 2.4, and 2.5 nM, respectively. As the response did not reach the maximal plateau, EC50 value for PCB118 could not be obtained. The TCDD-EC50 for BS AHR was as high as that for dioxin sensitive C57BL/6 mouse AHR. The in vitro dose responses were further analyzed following an established systematic framework and multiple (20, 50, and 80%) relative potencies (REPs) to the maximum TCDD response. The estimates revealed lower REP ranges (20-80%) of PeCDD and PeCDF for BS AHR than for mouse AHR. Average of the 20, 50, and 80% REPs was designated as Baikal seal specific TCDD induction equivalency factor (BS IEF). The BS IEFs of PeCDD, TCDF, PeCDF, PCB126, and PCB118 were estimated as 0.010, 0.018, 0.0078, 0.0059, and 0.00010, respectively. Total TCDD induction equivalents (IEQs) that were calculated using BS IEFs and hepatic concentrations in wild Baikal seals corresponded to only 12-31% of 2005 WHO TEF-derived TEQs. Nevertheless, about 50% of Baikal seals accumulated IEQs over the TCDD-EC50 obtained in this study. This assessment was supported by the enhanced CYP1A1 mRNA expression found in 50% of the specimens contaminated over the TCDD-EC50. These findings suggest that the IEFs proposed from this in vitro assay could be used to predict AHR-mediated responses in wild seals.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Benzofurans; Chlorocebus aethiops; COS Cells; Cytochrome P-450 CYP1A1; Dioxins; Environmental Pollutants; Forecasting; Liver; Mice; Receptors, Aryl Hydrocarbon; Seals, Earless

An egg injection study was conducted to confirm a proposed model of relative sensitivity of three avian species to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like chemicals. It was previously reported that the order of species sensitivity to in ovo exposure to TCDD, 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), or 2,3,7,8-tetrachlorodibenzofuran (TCDF) at doses ranging from 0.044 to 37 picomoles (pmol)/g egg was the chicken (Gallus gallus domesticus), common pheasant (Phasianus colchicus), and Japanese quail (Coturnix japonica) based on embryo mortality and hepatic enzyme induction. In the present study, the incidence of developmental deformities, changes in body and relative organ masses, and organ pathology of hatchlings as additional indicators of species sensitivity were assessed; in addition, embryo mortality in the three species was categorized by stage of development. Embryo mortality varied temporally with significant increases generally occurring after organogenesis and just prior to hatching. A significant increase in the percentage of developmental deformities was observed only in Japanese quail exposed to TCDF. Body and relative organ masses of quail, pheasants, and chickens dosed in ovo with TCDD, PeCDF, or TCDF were not consistently affected. Chemical-related pathology occurred only in livers of quail at the greatest doses of each compound. These results indicated that the incidence of developmental deformities, changes in body and relative organ masses and organ pathology could not be used as indicators of species sensitivity or chemical potency.

Topics: Animals; Benzofurans; Body Size; Brain; Chick Embryo; Coturnix; Embryo, Nonmammalian; Embryonic Development; Enzyme Induction; Galliformes; Liver; Myocardium; Organ Size; Ovum; Polychlorinated Dibenzodioxins; Spleen

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a prototypical environmental contaminant with neurotoxic properties that alters neurodevelopment and behavior. TCDD is a ligand of the aryl hydrocarbon receptor (AhR), which is a key signaling molecule to fully understand the toxic and carcinogenic properties of dioxin. Much effort is underway to unravel the molecular mechanisms and the signaling pathways involved in TCDD-induced neurotoxicity, and to define its molecular targets in neurons. We have used cerebellar granule cells (CGC) from wild-type (AhR+/+) and AhR-null (AhR-/-) mice to characterize the cell death that takes place in neurons after TCDD toxicity. TCDD induced cell death in CGC cultures from wild-type mice with an EC(50) of 127±21 nM. On the contrary, when CGC neurons from AhR-null mice were treated with TCDD no significant cell death was observed. The role of AhR in TCDD-induced death was further assessed by using the antagonists resveratrol and α-naphtoflavone, which readily protected against TCDD toxicity in AhR+/+ CGC cultures. AhR+/+ CGC cultures treated with TCDD showed nuclear fragmentation, DNA laddering, and increased caspase 3 activity, similarly to what was found by the use of staurosporine, a well-established inducer of apoptosis. Finally, the AhR pathway was active in CGC because TCDD could induce the expression of the target gene cytochrome P450 1A2 in AhR+/+ CGC cultures. All together these results support the hypothesis that TCDD toxicity in CGC neurons involves the AhR and that it takes place mainly through an apoptotic process. AhR could be then considered a novel target in neurotoxicity and neurodegeneration whose down-modulation could block certain xenobiotic-related adverse effects in CNS.

Topics: Animals; Apoptosis; Benzofurans; Caspase 3; Cells, Cultured; Cerebellum; Cytochrome P-450 CYP1A2; Dose-Response Relationship, Drug; Environmental Pollutants; Indoles; Mice; Mice, Knockout; Neurons; Reactive Oxygen Species; Receptors, Aryl Hydrocarbon; Tetrazolium Salts; Thiazoles; Trypan Blue

The aryl hydrocarbon receptor (AHR) mediates the toxic effects of halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PeCDF) and 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF). Non-traditional activators, including omeprazole (Omp), are thought to regulate AHR action through phosphorylation rather than binding to the receptor. In this study, we examined the ability of these compounds to induce AHR-dependent regulation of cytochrome P450 1A1 (CYP1A1) and CYP1B1 in T-47D human breast cancer cells. The role of Y322, a residue implicated in Omp-dependent activation of AHR was also investigated. All four compounds induced CYP1A1 and CYP1B1 mRNA expression, with Omp differing from the HAHs. Chromatin immunoprecipitation assays revealed ligand- and gene-selectivity in the recruitment patterns of AHR coactivators. We also found that residue Y322 of human AHR was important for maximum activation of AHR by 2,3,7,8-TCDD and 2,3,4,7,8-PeCDF, but required for 2,3,7,8-TCDF and Omp in an AHR-deficient MCF-7 human breast cancer cell line. In summary, this study provides evidence for context- and ligand-selective differences in coactivator recruitment in AHR-regulated gene expression and reveal an important role of Y322 in AHR activation.

Topics: Aryl Hydrocarbon Hydroxylases; Basic Helix-Loop-Helix Transcription Factors; Benzofurans; Cell Line, Tumor; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; Gene Expression Regulation, Enzymologic; Humans; Ligands; Omeprazole; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Tyrosine

Toxicogenomics was used to examine mRNA expression profiles obtained from primary rat hepatocytes treated for 24h with 0.01 or 1.0 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), 0.02 or 2.0 nM 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PeCDF) and 0.1 or 10nM 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF). The concentrations of 2,3,4,7,8-PeCDF and 2,3,7,8-TCDF were chosen to be equivalent to 2,3,7,8-TCDD's concentration based on the toxic equivalency factor/toxic equivalent (TEF/TEQ) method for estimating biological potency. 2,3,7,8-TCDD at 1.0 nM altered the expression of 533 genes; 2,3,4,7,8-PeCDF at 2.0 nM altered 182 genes, and 2,3,7,8-TCDF at 10nM altered 154 genes. Of these, 57 genes were affected by all three congeners. Agglomerative hierarchical clustering revealed distinct congener-dependent gene subclusters. Principal components analyses of the microarray data revealed that these congeners cluster independently of one another. Data presented here demonstrate that equivalent TEQ concentrations of 2,3,7,8-TCDD, 2,3,4,7,8-PeCDF and 2,3,7,8-TCDF, while altering the expression of a small battery of genes in common, also produce substantial congener specific alterations in gene expression.

Topics: Animals; Benzofurans; Female; Gene Expression Regulation; Hepatocytes; Multigene Family; Oligonucleotide Array Sequence Analysis; Polychlorinated Dibenzodioxins; Principal Component Analysis; Rats; Rats, Sprague-Dawley; Receptors, Aryl Hydrocarbon; RNA, Messenger

Relative potencies of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 2,3,7,8-tetrachlorodibenzofuran (TCDF) were determined in vitro in primary hepatocyte cultures of chicken (Gallus gallus), ring-necked pheasant (Phasianus colchicus), and Japanese quail (Coturnix japonica) embryos. Concentration-dependent effects on ethoxyresorufin O-deethylase (EROD) activity and expression of cytochrome P4501A4 and cytochrome P4501A5 (CYP1A4 and CYP1A5) messenger RNA (mRNA) were determined in hepatocytes exposed to serial dilutions of TCDD, PeCDF, or TCDF for 24 h. In chicken hepatocytes, the three compounds were equipotent inducers of EROD activity and CYP1A4/CYP1A5 mRNA expression. However, in ring-necked pheasant and Japanese quail hepatocytes, PeCDF was more potent than TCDD (3- to 5-fold in ring-necked pheasant and 13- to 30-fold in Japanese quail). Among species, the rank order of sensitivity (most to least) to EROD and CYP1A4/CYP1A5 mRNA induction for TCDD and TCDF was chicken > ring-necked pheasant > Japanese quail. In contrast, the three species were approximately equisensitive to EROD and CYP1A4/CYP1A5 mRNA induction by PeCDF. It has generally been assumed that TCDD is the most potent "dioxin-like compound" (DLC) and that the chicken is the most sensitive avian species to CYP1A induction by all DLCs. This study indicates that PeCDF is more potent than TCDD in ring-necked pheasant and Japanese quail hepatocytes and that ring-necked pheasant, Japanese quail, and chicken hepatocytes are equally sensitive to CYP1A induction by PeCDF.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Benzofurans; Birds; Cells, Cultured; Chickens; Coturnix; Cytochrome P-450 CYP1A1; Enzyme Induction; Galliformes; Hepatocytes; Polychlorinated Dibenzodioxins; RNA, Messenger

Ethoxyresorufin O-deethylase (EROD) activity was measured in primary cultures of ring-necked pheasant (Phasianuscolchicus) and Japanese quail (Coturnix japonica) embryonic hepatocytes exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) for 12, 24, 36 and 48 h. In ring-necked pheasant hepatocytes there was a significant time-dependent increase in the EROD-inducing potency of TCDD, PeCDF and TCDF (i.e. decrease of the EC50). In Japanese quail hepatocytes there was no time-dependent change in the EROD-inducing potency of TCDD, PeCDF and TCDF. There was no time-dependent change in the relative potency of PeCDF and TCDF (i.e. compared to the potency of TCDD) in ring-necked pheasant hepatocytes and of PeCDF in Japanese quail hepatocytes. The results indicate that the relative potencies of these compounds at 24h are representative of their relative potencies between 12 and 48 h. However, in Japanese quail hepatocytes, the relative potency of TCDF decreased in a time-dependent manner (up to 3.6-fold difference). These results suggest that the effect of time on the EROD-inducing potency of TCDD, PeCDF and TCDF in ring-necked pheasant and Japanese quail hepatocytes is compound- and species-specific, but experimental conditions could also be involved in the differences observed.

Topics: Animals; Benzofurans; Cells, Cultured; Coturnix; Cytochrome P-450 CYP1A1; Dose-Response Relationship, Drug; Enzyme Induction; Galliformes; Hepatocytes; Polychlorinated Dibenzodioxins

The toxic equivalency factor (TEF) approach recommended by the World Health Organization is used to quantify dioxin-like exposure concentrations for mixtures of polychlorinated dibenzo-dioxins, -furans, and polychlorinated biphenyls (PCBs), including 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Whole-genome microarrays were used to evaluate the hepatic gene expression potency of TCDF and PCB126 relative to TCDD with complementary histopathology, tissue level analysis, and ethoxyresorufin-O-deethylase (EROD) assay results. Immature ovariectomized C57BL/6 mice were gavaged with 0.001, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, and 300 μg/kg TCDD and TEF-adjusted doses (TEF for TCDF and PCB126 is 0.1) of TCDF or PCB126 (1, 3, 10, 30, 100, 300, 1000, and 3000 μg/kg of TCDF or PCB126) or sesame oil vehicle and sacrificed 24 h post dose. In general, TCDD, TCDF, and PCB126 tissue levels, as well as histopathological effects, were comparable when comparing TEF-adjusted doses. Automated dose-response modeling (ToxResponse Modeler) of the microarray data identified 210 TCDF and 40 PCB126 genes that exhibited sigmoidal dose-response curves with comparable slopes when compared with TCDD. These similar responses were used to calculate a median TCDF gene expression relative potency (REP) of 0.06 and a median PCB126 gene expression REP of 0.02. REPs of 0.02 were also calculated for EROD induction for both compounds. Collectively, these data suggest that differences in the ability of the liganded aryl hydrocarbon receptor:AhR nuclear translocator complex to elicit differential hepatic gene expression, in addition to pharmacokinetic differences between ligands, influence their potency in immature ovariectomized C57BL/6 mice.

Topics: Animals; Benzofurans; Cytochrome P-450 CYP1A1; Dose-Response Relationship, Drug; Environmental Pollutants; Female; Gene Expression; Ligands; Liver; Mice; Mice, Inbred C57BL; Oligonucleotide Array Sequence Analysis; Organ Size; Ovariectomy; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; RNA, Messenger; Toxicogenetics

The concentration dose response for aryl hydrocarbon receptor (AHR)-mediated CYP1A1 and CYP1A2 messenger RNA (mRNA) induction and enzyme activity was determined in primary cultures of rat and human hepatocytes for 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,4,7,8-pentachlorodibenzofuran, and 2,3,7,8-tetrachlorodibenzofuran. Eleven different congener concentrations from 0.00001 to 100 nM were used, thus spanning seven orders of magnitude. The Hill model was used to obtain values of EC(x) and maximal response from the individual data sets. No-observed effect concentration values were derived using several statistical methods including Dunnett's test, the Welch-Aspin test, and step-down bilinear regression. Thresholds were estimated using baseline projection methods and a "hockey stick" fitting method. Human hepatocytes were less responsive and less sensitive with respect to CYP1A1 activity and mRNA induction than rats. On the other hand, the human CYP1A2 response was more robust than the response in rats but generally less sensitive. These data allow an evaluation of relative species sensitivities for developing interspecies toxicodynamic adjustment factors, for assessing AHR activation thresholds, and for evaluating relative congener potencies. Overall, these data support the position that humans are less sensitive than rats to these AHR-dependent end points and support the use of a data-derived adjustment factor of 1.0 or less for extrapolating between rats and humans.

Topics: Animals; Benzofurans; Cells, Cultured; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Dose-Response Relationship, Drug; Environmental Pollutants; Enzyme Induction; Gene Expression Regulation, Enzymologic; Hepatocytes; Humans; No-Observed-Adverse-Effect Level; Polychlorinated Dibenzodioxins; Rats; Receptors, Aryl Hydrocarbon; Risk Assessment; Species Specificity

Persistent organic pollutants such as halogenated aromatic hydrocarbons (HAHs) biomagnify in food webs and accumulate to high concentrations in top predators like odontocete cetaceans (toothed whales). The most toxic HAHs are the 2,3,7,8-substituted halogenated dibenzo-p-dioxins and furans, and non-ortho-substituted polychlorinated biphenyls (PCBs), which exert their effects via the aryl hydrocarbon receptor (AHR). Understanding the impact of HAHs in wildlife is limited by the lack of taxon-specific information about the relative potencies of toxicologically important congeners. To assess whether Toxic Equivalency Factors (TEFs) determined in rodents are predictive of HAH relative potencies in a cetacean, we used beluga and mouse AHRs expressed in vitro from cloned cDNAs to measure the relative AHR-binding affinities of ten HAHs from five different structural classes. The rank order of mean IC(50)s for competitive binding to beluga AHR was: TCDD

Topics: Animals; Beluga Whale; Benzofurans; Binding, Competitive; Endangered Species; Environmental Pollutants; Hydrocarbons, Aromatic; Mice; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Risk Assessment

Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls that have toxic equivalency factors (TEFs) were measured in serum of 946 subjects in five Michigan counties. The study was motivated by concerns about human exposure to dioxin-contaminated sediments in the Tittabawassee River (TR). Most of the toxic equivalency in TR sediments is from two furan congeners, 2,3,7,8-tetrachlorodibenzofuran and 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-pentaCDF).. The individual with the highest adjusted (for age, age squared, and body mass index) serum level of 2,3,4,7,8-pentaCDF in the study (42.5 ppt) reported a unique history of raising cattle and vegetables in the floodplain of the TR. Interviews and serum samples were obtained from the index case and 15 other people who ate beef and vegetables raised by the index case. 2,3,4,7,8-pentaCDF in beef lipid was estimated to have been more than three orders of magnitude greater than background (1,780 vs. 1.1 ppt). The mean, median, and 95th percentile for serum 2,3,4,7,8-pentaCDF in the study control population were 6.0, 5.4, and 13.0 ppt, respectively, and were 9.9, 8.4, and 20.5 ppt among beef and vegetable consumers, respectively. Back extrapolation for the index case suggests that his increase in serum concentration of 2,3,4,7,8-pentaCDF above background may have been as high as 146 ppt.. Consumption of beef and/or vegetables raised on dioxin-contaminated soil may be an important completed pathway of exposure. RELEVANCE TO PUBLIC HEALTH PRACTICE: Animals and crops should not be raised for human consumption in areas contaminated with dioxins.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Animals; Benzofurans; Cattle; Humans; Michigan; Middle Aged; Soil Pollutants; Young Adult

As part of an ongoing effort to understand aryl hydrocarbon receptor (AhR) mediated toxicity in mink, cDNAs encoding for CYP1A1 and the CYP1A2 mixed function monooxygenases were cloned and characterized. In addition, the effects of selected dibenzofurans on the expression of these genes and the presence of their respective proteins (P4501A) were investigated, and then correlated with the catalytic activities of these proteins as measured by ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-deethylase (MROD) activities. The predicted protein sequences for CYP1A1 and CYP1A2 comprise 517 and 512 amino acid residues, respectively. The phylogenetic analysis of the mink CYP1As with protein sequences of other mammals revealed high sequence homology with sea otter, seals and the dog, with amino acid identities ranging from 89 to 95% for CYP1A1 and 81 to 93% for CYP1A2. Since exposure to both 2,3,7,8-Tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-Pentachlorodibenzofuran (PeCDF) resulted in dose-dependent increases of CYP1A1 mRNA, CYP1A2 mRNA and CYP1A protein levels an underlying AhR-mediated mechanism is suggested. The up-regulation of CYP1A mRNA in liver was more consistent to the sum adipose TEQ concentration than to the liver TEQ concentration in minks treated with TCDF or PeCDF. The result suggested that the hepatic-sequestered fraction of PeCDF was biologically inactive to the induction of CYP1A1 and CYP1A2.

Topics: Animals; Benzofurans; Blotting, Western; Cloning, Molecular; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Environmental Pollutants; Enzyme Induction; Female; Kinetics; Liver; Mink; Oxazines; Phylogeny; Receptors, Aryl Hydrocarbon; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Analysis, DNA; Sequence Analysis, Protein; Sequence Homology, Amino Acid; Substrate Specificity

Mink are often used as a sentinel species in ecological risk assessments of chemicals such as polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) that cause toxicity mediated through the aromatic hydrocarbon receptor. Considerable toxicological information is available on the effects of PCBs and PCDDs on mink, but limited toxicological information is available for PCDFs. Thus, exposure concentrations at which adverse effects occur could not be determined reliably for complex mixtures in which PCDFs dominate the total calculated concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (TEQ). Two studies were conducted to evaluate the potential toxicity of PCDFs to mink. The first was a chronic exposure, conducted under controlled laboratory conditions, in which mink were exposed to 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) concentrations as great as 2.4 x 10(3) ng 2,3,7,8-TCDF/kg wet-weight (ww) diet or 2.4 x 10(2) ng TEQ(2006-WHO-mammal)/kg ww diet. In that study, transient decreases in body masses of kits relative to the controls was the only statistically significant effect observed. The second study was a 3-y field study during which indicators of individual health, including hematological and morphological parameters, were determined for mink exposed chronically to a mixture of PCDDs and PCDFs under field conditions. In the field study, there were no statistically significant differences in any of the measured parameters between mink exposed to a median estimated dietary dose of 31 ng TEQ(2006-WHO-mammal)/kg ww and mink from an upstream reference area where they had a median dietary exposure of 0.68 ng TEQ(2006-WHO-mammal)/kg ww. In both studies, concentrations of TEQ(2006-WHO-mammal) to which the mink were exposed exceeded those at which adverse effects, based on studies with PCDD and PCB congeners, would have been expected. Yet in both instances where PCDF congeners were the sole or predominant source of the TEQ(2006-WHO-mammal), predicted adverse effects were not observed. Taken together, the results of these studies suggest that the values of the mammalian-specific toxicity equivalency factors suggested by the World Health Organization overestimate the toxic potency of PCDFs to mink. Therefore, hazard cannot be accurately predicted by making comparisons to toxicity reference values derived from exposure studies conducted with PCBs or PCDDs in situations where mink are exposed to TEQ mixtures dominated

Topics: Animals; Benzofurans; Dibenzofurans, Polychlorinated; Dose-Response Relationship, Drug; Ecosystem; Environmental Pollutants; Female; Male; Michigan; Mink; Population Dynamics; Time Factors

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) was applied to the trace analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). To determine the optimum wavelength for analysis of PCDD/Fs, the wavelength of the femtosecond laser utilized for multiphoton ionization was converted to near-ultraviolet status using stimulated Raman scattering. A femtosecond laser emitting at 300 nm completely eliminated the background signal arising from the bleeding compounds generated from a stationary phase of the capillary column in GC.

Topics: Air Pollutants; Benzofurans; Dibenzofurans, Polychlorinated; Dioxins; Gas Chromatography-Mass Spectrometry; Lasers; Polychlorinated Dibenzodioxins; Sensitivity and Specificity; Spectrum Analysis, Raman; Temperature; Time Factors; Ultraviolet Rays

The toxic equivalent (TEQ) approach is traditionally used in risk evaluation of dioxins. Non-dioxin-like PCBs are not included in this approach and TEQ can therefore underestimate toxicity. In this study, a factorial design and multiple endpoint strategy have been used to evaluate the combined toxicity and possible interactions between the non-dioxin-like PCB 138 and the potent AhR agonists 2,3,7,8-TCDF (TCDF) and 1,2,3,7,8-PeCDD (PCDD). Primary hepatocyte cultures from Atlantic salmon were exposed for 24h and qPCR was employed to create CYP1A dose-response curves and to quantify the transcriptional levels of eight genes (CYP1A, UDPGT, HSP70, GR, GPX, MnSOD, GST and p53). Principal component analysis (PCA) was used to evaluate response similarities between genes. PLS regression was used to model CYP1A and UDPGT responses to the three chemicals. The contour plot examinations of the CYP1A model indicated an antagonism between PCDD and TCDF and in the UDPGT model a possibly synergistic interaction between PCB 138 and PCDD. The results indicate that PCB 138, in combination with TCDF and PCDD, can contribute to the measured CYP1A and UDPGT responses. Using primary cell cultures, multivariate data analysis of qPCR data is shown to be a useful tool in toxicological studies. A multiple endpoints strategy can enhance the quality of risk evaluation of chemical compounds.

Topics: Animals; Benzofurans; Cells, Cultured; Cytochrome P-450 CYP1A1; Dose-Response Relationship, Drug; Endpoint Determination; Glucuronosyltransferase; Hepatocytes; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Principal Component Analysis; RNA, Messenger; Salmo salar

Toxic equivalency factors (TEFs) are assigned to dioxin-like chemicals based on relative potency (REP) values of individual adaptive and toxic responses compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Agilent 4x44K oligonucleotide microarrays were used to examine the hepatic gene expression potency of 2,3,7,8-tetrachlorodibenzofuran (TCDF), relative to TCDD with complementary histopathology, TCDD and TCDF tissue level analysis, and ethoxyresorufin-O-deethylase (EROD) assay data. Immature ovariectomized C57BL/6 mice were gavaged with 0.03, 0.1, 0.3, 1, 3, 10, 30, or 100 microg/kg TCDD, the World Health Organization TEF-adjusted doses (10 x TCDD dose) of TCDF (0.3, 1, 3, 10, 30, 100, or 300 microg/kg), or sesame oil vehicle and killed at 72 h. Two thousand two hundred eighty-eight and 1347 genes were differentially expressed (P1(t) > 0.90) at one or more doses by TCDD and TCDF, respectively. Automated dose-response modeling (ToxResponse Modeler) identified a total of 1027 and 837 genes with either a sigmoidal, exponential, linear, Gaussian, or quadratic dose-response relationship 72 h after treatment in TCDD and TCDF, respectively. Two hundred seventy genes exhibited a sigmoidal TCDD-induced dose-response (ED(50s) from 0.08 to 42.2 microg/kg) compared to only 179 sigmoidal responsive genes (ED(50s) from 0.74 to 299.9 microg/kg) elicited by TCDF. Of the 1027 TCDD dose-responsive genes, 654 were not examined further due to the lack of a dose response elicited by TCDF. Of the 373 genes that exhibited a TCDD and TCDF dose response, REPs were calculated for the 83 genes that exhibited comparable sigmoidal curve shapes and slopes. The median REP for these 83 genes was 0.10, with a maximum REP of 0.56 and a minimum of 0.01. REPs of 0.04 were also calculated for EROD and increase in relative liver weight (RLW) at 72 h. Collectively, the lower number of TCDF-induced genes compared to TCDD and the 0.04 REPs for EROD activity and increased RLW are not consistent with the TEF of 0.10 for the hepatotoxicity of TCDF in C57BL/6 mice at 72 h.

Topics: Animals; Automation; Benzofurans; Body Weight; Dose-Response Relationship, Drug; Female; Gene Expression Profiling; Liver; Mice; Mice, Inbred C57BL; Organ Size; Polychlorinated Dibenzodioxins; Polymerase Chain Reaction

Wild mink (Mustela vison) living along the Tittabawassee River in central Michigan exhibit elevated hepatic and dietary polychlorinated dibenzofuran (PCDF) concentrations exceeding mink-specific, literature-reported toxicity reference values (TRVs) on a toxicity equivalents basis. However, no apparent effects on individuals or population are evident, suggesting that available TRVs may overpredict risk for the site-specific mix of congeners. To investigate this discrepancy, a 180-day spiked feed study was conducted to assess: (1) the dosages of key congeners necessary to achieve liver concentrations bracketing those observed in wild mink, (2) time to achieve steady-state concentrations, and (3) effect of coadministration of 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF) on the toxicokinetics and distribution of each congener. Adipose and hepatic PCDF concentrations were measured at 0, 90, and 180 days. PCDF concentrations in mink scat were determined at several time points and indicated nearly complete absorption of both TCDF and 4-PeCDF from the diet. Elimination half-times of TCDF were < 15 h and were inversely proportional to dose, while those for 4-PeCDF were approximately 7-9 days with no clear dose dependency in the tested dose range. Coadministration of 4-PeCDF and TCDF accelerated clearance of TCDF compared to administration of TCDF alone. Clearance of 4-PeCDF was not affected by TCDF coadministration. Distribution of 4-PeCDF, but not TCDF, demonstrated increased hepatic sequestration with increasing dose. 4-PeCDF toxicokinetics were described using a previously published two-compartment model. Overall, the toxicokinetic information gathered here illustrates the impact of CYP1A1 induction on bioaccumulation and toxicity potential of TCDF and 4-PeCDF. This information may provide insight into why the current TRVs do not appear to correctly characterize the risk for these two congeners when they are the primary components of an environmental mixture.

Topics: Adipose Tissue; Animals; Benzofurans; Ecology; Female; Liver; Mink; Models, Biological

Temporal analyses were performed on hepatic tissue from immature female C57BL/6 mice in order to compare the gene expression profiles for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibzofuran (TCDF). Time course studies conducted with a single oral dose of 300 microg/kg TCDF or 30 microg/kg TCDD were used to compare differential gene expression on complementary DNA microarrays containing 13,361 features, representing 8194 genes at 2, 4, 8, 12, 24, 72, 120, and 168 h. One hundred and ninety-five genes were identified as differentially regulated by TCDF, of which 116 genes were in common with TCDD, with 109 exhibiting comparable expression profiles (correlation coefficients > 0.3). In general, TCDF was less effective in eliciting hepatic vacuolization, and differential gene expression compared with TCDD when given at an equipotent dose based on a toxic equivalence factor (TEF) of 0.1 for TCDF, especially 72-h postadministration. For example, the induction of Cyp1a1 messenger RNA by TCDF was less when compared TCDD. Moreover, TCDF induced less severe hepatocyte cytoplasmic vacuolization consistent with lower lipid accumulations which significantly subsided by 120 and 168 h when compared with TCDD. TCDF-elicited responses correlated with their hepatic tissue levels which gradually decreased between 18 and 168 h. Although both compounds elicited comparable gene expression profiles, especially at early time points, the TCDF responses were generally weaker. Collectively, these results suggest that the weaker TCDF responses could be attributed to differences in pharmacokinetics. However, more comprehensive dose-response studies are required at optimal times for each end point of interest in order to investigate the effect of pharmacokinetic differences on relative potencies that are important in establishing TEFs.

Topics: Administration, Oral; Animals; Benzofurans; Environmental Pollutants; Female; Gene Expression Profiling; Gene Expression Regulation; Hepatocytes; Liver; Mice; Mice, Inbred C57BL; Oligonucleotide Array Sequence Analysis; Polychlorinated Dibenzodioxins; RNA, Messenger; Time Factors; Toxicogenetics; Vacuoles

The present study clarifies the enzymatic properties of two avian cytochrome P4501A (CYP1A) paralogs, CYP1A4 and 1A5, using a yeast-based vector system. Recombinant CYP1A4 and 1A5 proteins from common cormorant (Phalacrocorax carbo) were expressed in yeast cells, and showed typical reduced CO-difference spectra with a peak at 446 nm. Kinetic analysis of O-dealkylase of methoxy-, ethoxy-, pentoxy- and benzyloxyresorufin catalyzed by the CYP1A enzymes revealed that Vmax value for ethoxyresorufin-O-deethylase (EROD) activity was much higher than that for the other three O-dealkylase activities for both isozymes. Interestingly, remarkable substrate specificity of the CYP1As was observed for O-dealkylation of benzyloxyresorufin and methoxyresorufin; CYP1A4 was highly specific for catalyzing benzyloxyresorufin-O-debenzylase activity, whereas CYP1A5 was more efficient in catalyzing methoxyresorufin-O-demethylase activity. The present study also measured CYP1A-dependent EROD activity in the presence of 2,3,7,8-tetrachlorodibenzofuran (TCDF) to evaluate the ability of this dioxin-like congener to inhibit the EROD activity. One hundred nanomolar TCDF noncompetitively inhibited CYP1A5-dependent EROD activity, although no inhibitory effect was detected for CYP1A4-dependent EROD activity. These results indicate that the avian CYP1A paralogs have different affinities for substrate and inhibitor, thus suggesting their distinct physiological and toxicological roles.

Topics: Animals; Avian Proteins; Benzofurans; Birds; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Kinetics; Liver; Water Pollutants, Chemical; Yeasts

Charge-exchange reactions involving benzene have been successfully exploited to increase the sensitivity of atmospheric-pressure chemical ionization mass spectrometry (APCI-MS) towards hydrophobic compounds of significant environmental relevance which are not detectable with the ordinary APCI techniques. Among them, good sensitivity have been found for (a) highly chlorinated biphenyl derivatives such as dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethene (DDE); (b) cyclopentadienes such as Aldrin and its epoxy derivatives Dieldrin and Endrin; and (c) dibenzofurans and dibenzo-para-dioxins such as 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) and 2,3,7,8-tetrachloro-dibenzo-para-dioxin (2,3,7,8-TCDD). The reactant benzene molecules were introduced into the source either through the nebulizer gas or by direct post-column addition of neat liquid, whereas the targeted compounds were analyzed using a high-performance liquid chromatography (HPLC) RP-18 column using methanol/water solutions as mobile phase. By using benzene as post-column reagent, positive ion mode detection was proven to be significantly enhanced as compared with APCI measurements carried out without benzene assistance.

Topics: Air Pollutants; Aldrin; Atmosphere; Benzene; Benzofurans; Chromatography, High Pressure Liquid; DDT; Dichlorodiphenyl Dichloroethylene; Dichlorodiphenyldichloroethane; Environmental Monitoring; Hydrophobic and Hydrophilic Interactions; Polychlorinated Dibenzodioxins; Spectrometry, Mass, Electrospray Ionization

The transport processes of seventeen 2,3,7,8-chlorinated congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from their major sources to humans were modeled to estimate the time course, from the past to the future, of the human health risk to the Japanese population. The comparison between measured and estimated values showed that the present modeling approach represented the background levels of congeners in the environment, daily intake, and body burden reasonably well, except for in the case of 2,3,7,8-TCDF. Although PCDD/Fs in herbicides have contributed greatly to the daily intake and body burden to the Japanese population in the past, the main sources of the present intake and burden of PCDD/Fs is estimated to be incinerators. The margin of exposure (MOE) for the risk of morphological reproductive alteration in female offspring exposed prenatally was calculated based on the estimated maternal body burden. The results indicated that the MOE values were in the single digits, implying that these values may not be sufficiently large to guarantee the safety of female offspring of mothers born in the 1950s, whereas the MOE values for female offspring born in and after the latter half of the 1990s may be sufficiently large to guarantee safety.

Topics: Adult; Benzofurans; Body Burden; Dibenzofurans, Polychlorinated; Dioxins; Environmental Exposure; Environmental Pollutants; Female; Humans; Incineration; Japan; Models, Theoretical; Polychlorinated Dibenzodioxins; Public Health; Reproduction; Risk Assessment; Safety; Soil Pollutants

New Bedford Harbor (NBH), MA, is a federal Superfund site that is heavily contaminated with polychlorinated biphenyls (PCBs) and other halogenated aromatic hydrocarbons (HAHs), including some potent aryl hydrocarbon receptor (AhR) agonists. A population of Atlantic killifish (Fundulus heteroclitus) continues to inhabit this site, despite accumulating extraordinarily high concentrations of PCBs (272 microg/g dry weight). To determine if NBH killifish have developed resistance to HAHs that act through the AhR, we examined the inducibility of cytochrome P4501A1 (CYP1A1), UDP glucuronosyl transferase (UGT), and glutathione S-transferase (GST) in fish from NBH and a reference site, Scorton Creek (SC, Cape Cod, MA; PCB concentrations 0.177 microg/g dry weight). 2,3,7,8-Tetrachlorodibenzofuran (TCDF) induced CYP1A1 mRNA, protein, and activity in SC fish in all tissues examined (liver, heart, gut, gill, kidney, spleen, and gonad). In contrast, NBH fish expressed low levels of CYP1A1 and showed no induction of CYP1A1 mRNA, protein, or activity by TCDF, or induction that was lower in magnitude or required higher doses of inducer. p-Nitrophenol UGT activity was not induced by TCDF in either population, while GST activity with 1-chloro-2,4-dinitrobenzene as substrate was induced only in NBH fish in one experiment. Inducibility of CYP1A1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or beta-naphthoflavone (BNF) was measured in primary hepatocyte cultures prepared from SC and NBH fish. TCDD induced CYP1A1 activity (ethoxyresorufin O-deethylase) to the same degree in hepatocytes from both populations, demonstrating the functionality of the AhR signaling pathway in NBH fish. However, hepatocytes from NBH fish were 14-fold less sensitive to TCDD than were those from SC fish. The nonhalogenated AhR agonist BNF also induced CYP1A1 in cells from both populations, although with only a 3-fold difference in sensitivity (NBH < SC). These results indicate that chronic exposure to high levels of HAHs has led to a reduction in the sensitivity of NBH killifish to AhR agonists. The resistance is systemic and pretranslational, and exhibits compound-specific differences in magnitude. These findings suggest an alteration in the AhR signal transduction pathway in NBH fish.

Topics: Animals; Benzofurans; beta-Naphthoflavone; Body Weight; Cells, Cultured; Cytochrome P-450 CYP1A1; Drug Tolerance; Enzyme Induction; Female; Glucuronosyltransferase; Glutathione Transferase; Gonads; Hazardous Waste; Hepatocytes; Killifishes; Liver; Male; Microsomes; Organ Size; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; RNA, Messenger

Polychlorinated organic compounds (POCs) have been measured in Arctic cod liver from Vestertana Fjord for a period of 1987-1998. Significant decrease was observed for DDD (p = 0.043), alpha-HCH (p = 0.001), and gamma-HCH (lindane; p = 0.001). Contents of DDE, 2,3,7,8-tetrachlorodibenzofuran, PCBs, chlordanes, chloronaphthalenes, hexachlorobenzene and polychlorodiphenyl ethers had no significant trend. Contents of three hexa- and two heptachlorodibenzofurans and octachlorodibenzofuran increased slightly from 1987 to 1994, but then at very high rate from 1994 to 1998. Trends of HCHs, profiles of PCBs and levels of chlordanes are in accordance with atmospheric long range transport. The hexa-, hepta- and octachlorodibenzofurans observed are major impurities in chlorophenol formulation Ky-5, which has been used as wood preservative and as fungicide/slimicide in industrial processes. Their profile in Vestertana cod was similar to that observed in Ky-5 contaminated fish.

Topics: Animals; Arctic Regions; Benzofurans; DDT; Environmental Monitoring; Fishes; Hexachlorocyclohexane; Hydrocarbons, Chlorinated; Liver; Longitudinal Studies; Pesticides; Polychlorinated Biphenyls

beta-Naphthoflavone (beta-NF) is a widely used inducer of phase-I and phase-II enzymes controlled by aryl hydrocarbon receptor (AhR). Studies of competitive binding with (3)H-labelled 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), 3-methylcholanthrene (3-MC) and benzo[a]pyrene (B[a]P) have shown that beta-NF is a high-affinity ligand for AhR and also for polycyclic aromatic hydrocarbon (PAH)-binding protein, both soluble proteins of rat liver in 8 S and 4 S fractions, respectively, of sucrose gradients. This study examined binding of [(3)H]beta-NF to liver cytosolic proteins of female Sprague-Dawley rats. Treatment of rats with beta-NF, 3-MC, TCDD or alpha-naphthoflavone (alpha-NF) increased the specific [(3)H]beta-NF binding to liver cytosol up to 125-fold that of vehicle (corn oil)-treated rats (<100 fmol/mg of protein). Sucrose gradients revealed a large 4 S and a small 8 S peak of radioactivity from [(3)H]beta-NF binding to cytosols of beta-NF-, 3-MC-, TCDD- or alpha-NF-treated rats. Whereas co-incubation with the unlabelled beta-NF eliminated both peaks, co-incubation with 2,3, 7,8-tetrachlorodibenzofuran (TCDF) eliminated only the 8 S peak. The sucrose density gradient from [(3)H]TCDD binding to cytosol of beta-NF- or TCDD-treated rats yielded a small 4 S and a larger 8 S peak; only the latter was abolished by co-incubation with TCDF. Thus, the patterns of sedimentation, distribution and elimination of radioactivity from the 8 S fraction of the liver cytosols from beta-NF-, 3-MC-, TCDD- or alpha-NF-treated rats were characteristic for the AhR, whereas those from the 4 S fraction appeared specific for [(3)H]beta-NF binding. The data indicate that potent AhR agonists, TCDD, 3-MC and beta-NF, and to a lesser extent alpha-NF, a weak AhR agonist, induce a 4 S [(3)H]beta-NF-binding protein in liver cytosol of female rats. alpha-NF, beta-NF and 3-MC were effective competitors (80-85% inhibition) of the [(3)H]beta-NF-specific binding to the beta-NF-, 3 MC- or TCDD-induced 4 S protein, whereas several PAHs including B[a]P and benzo[e]pyrene were only weak competitors. The increased [(3)H]beta-NF binding was not associated with glycine N-methyltransferase activity. Hence, the 4 S [(3)H]beta-NF-binding protein described herein differs from the constitutive 4 S PAH-binding protein of rat liver cytosols in the inducibility by beta-NF and 3-MC, ligand-binding characteristics, and lack of glycine N-methyltransferase activity. Gel filtration on Sephacryl of liver cyt

Topics: Animals; Benzo(a)pyrene; Benzoflavones; Benzofurans; beta-Naphthoflavone; Binding, Competitive; Carrier Proteins; Cytochrome P-450 CYP1A1; Cytosol; Female; Glycine N-Methyltransferase; Kinetics; Liver; Methylcholanthrene; Methyltransferases; Molecular Weight; Polychlorinated Dibenzodioxins; Protein Binding; Rats; Rats, Sprague-Dawley; Receptors, Aryl Hydrocarbon

Models of receptor action are valuable for describing properties of ligand-receptor interactions and thereby contribute to mechanism-based risk assessment of receptor-mediated toxic effects. In order to build such a model for the aryl hydrocarbon receptor (AHR), binding affinities and CYP1A induction potencies were measured in PLHC-1 cells and were used to determine intrinsic efficacies for 10 halogenated aromatic hydrocarbons (HAH): 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7, 8-tetrachlorodibenzofuran (TCDF), and eight polychlorinated biphenyls (PCB). TCDD, TCDF, and non-ortho-substituted PCBs 77, 81, 126, and 169 behaved as full agonists and displayed high-intrinsic efficacy. In contrast, the mono- and di-ortho-substituted PCBs bound to the AHR but displayed lower or no intrinsic efficacy. PCB 156 was a full agonist, but with an intrinsic efficacy 10- to 50-fold lower than non-ortho-substituted PCBs. PCB 118 was a very weak partial agonist. PCBs 105 and 128 were shown to be competitive antagonists in this system. The model was then used to predict CYP1A induction by binary mixtures. These predictions were tested with binary mixtures of PCB 126, 128, or 156 with TCDD. Both PCB 156 (a low-intrinsic efficacy agonist) and PCB 128 (a competitive antagonist) inhibited the response to TCDD, while the response to TCDD and PCB126 was additive. These data support the following conclusions: 1) only 1-2% of the receptors in the cell need be occupied to achieve 50% of maximal CYP1A induction by one of the high-intrinsic efficacy agonists, demonstrating the existence of "spare" receptors in this system; 2) the insensitivity of fish to ortho-substituted PCBs is due to both reduced affinity and reduced intrinsic efficacy compared to non-ortho-substituted PCBs; 3) PCB congeners exhibit distinct structure-affinity and structure-efficacy relationships. Separation of AHR ligand action into the properties of affinity and intrinsic efficacy allows for improved prediction of the behavior of complex mixtures of ligands, as well as mechanistic comparisons across species and toxic endpoints.

Topics: Animals; Benzofurans; Binding, Competitive; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Environmental Pollutants; Enzyme Induction; Isoenzymes; Kinetics; Ligands; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Structure-Activity Relationship

A laboratory experiment was conducted to investigate the transfer of organic contaminants from an environmentally contaminated marine sediment through a simple marine food chain. The infaunal polychaete, Nereis virens, was exposed to contaminated sediment collected from the Passaic River, NJ, USA, for 70 days. These polychaetes were then fed to the American lobster, Homarus americanus, for up to 112 days. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), 2,4,6,8-tetrachlorodibenzothiophene (TCDT), polychlorinated biphenyls (PCBs), and several chlorinated pesticides were accumulated by polychaetes following exposure to the contaminated sediment. Some of these contaminants were also accumulated by lobsters which were exposed to the contaminated sediment and/or fed contaminated polychaetes. Only the lesser chlorinated PCDDs and PCDFs (mostly tetra- and pentachlorinated congeners) and 2,4,6,8-TCDT were detected in the polychaetes and lobster. Significant alterations were noted in the PCB patterns found in both species, particularly the lobster. The non-ortho-substituted PCBs (such as congeners 77 and 126) became enriched in the PCB mixtures of the polychaetes and especially the lobsters relative to the sediment, probably because these congeners were not metabolized. These congeners and the 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalents of the PCB mixtures were enriched by a factor of about six in the lobsters relative to the sediment. Elimination of PCB congeners containing vicinal hydrogens in the meta-para region is consistent with cytochrome P450IIB-type metabolism. Based on the concentration trends for some PCB congeners and chlorinated pesticide ratios measured in the lobsters during this experiment, it appears that this metabolic system is inducible in the American lobster.

Topics: Animals; Benzofurans; Dibenzofurans, Polychlorinated; Food Chain; Geologic Sediments; Nephropidae; Polychaeta; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Soil Pollutants; Thiophenes

We have characterized the spectrum of PCB contaminants in human milk samples from 95 women in Kazakhstan using GC/MS congener specific analysis. In these samples, 12 PCBs comprised 83% of total PCB concentration, and were similar to the major PCBs reported in other published human milk studies. By summing concentration levels of 80 PCB congeners in the Kazakhstan samples, a mean total PCB concentration of 368 ng/g fat was obtained. This is lower than levels reported in human milk samples from Western Europe. Six indicator PCBs were summed in Kazakh milk samples; their aggregate value was similar to literature values published for human milk from the former Soviet Union. Using WHO's recent TEF scheme, the mean sum of PCDD/F, coplanar PCB, mono-ortho PCB, and di-ortho PCB TEQ is 42 pg TEQ/g fat.

Topics: Benzofurans; Female; Gas Chromatography-Mass Spectrometry; Humans; Infant; Infant, Newborn; Kazakhstan; Milk, Human; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Soil Pollutants; World Health Organization

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a common environmental pollutant causing public concern. Its toxic effects include disruption of the immune, endocrine, and reproductive systems, impairment of fetal development, carcinogenicity, and lethality in rodents. Here, we report that TCDD induces apoptosis in two cultured human leukemic lymphoblastic T cell lines. This cell death was found not to be dependent on an aryl hydrocarbon receptor and to be inhibited by the inhibitor of tyrosine kinases and caspases. Apoptosis-linked c-Jun N-terminal kinase is rapidly activated in these cells by the treatment with TCDD. A dominant-negative mutant of c-Jun N-terminal kinase prevented cell death in the treatment with TCDD. Furthermore, TCDD decreases the Bcl-2 protein level in these cell lines. These findings will help in the understanding of the molecular mechanism underlying TCDD-mediated immunotoxicity.

Topics: Apoptosis; Aspartic Acid; Benzofurans; beta-Naphthoflavone; Calcium-Calmodulin-Dependent Protein Kinases; Cycloheximide; DNA Fragmentation; Environmental Pollutants; Enzyme Activation; Gene Expression Regulation, Neoplastic; Genistein; Humans; JNK Mitogen-Activated Protein Kinases; Lymphoma, T-Cell; Microscopy, Fluorescence; Mitogen-Activated Protein Kinases; Mutation; Polychlorinated Dibenzodioxins; Proto-Oncogene Proteins c-bcl-2; Receptors, Aryl Hydrocarbon; RNA, Messenger; Tumor Cells, Cultured

The AH receptor (AHR) is a ligand-activated transcription factor and member of a growing family of homologous proteins implicated in development. In this study we have characterized the actions of 2,3, 7,8-tetrachlorodibenzofuran (TCDF), a well-studied AHR ligand, and the expression of AHR and selected AHR signal transduction pathway genes in the developing mouse mammary gland. High levels of AHR protein were observed in the mammary glands of C57Bl/6J (AHR +/+) mice during estrous-stimulated growth and branching of terminal end buds (TEBs). Comparative analysis of mammary gland development in AHR -/- and +/+ littermates revealed a 50% reduction in TEBs and an increase in blunt-ended terminal ducts in the AHR null animals. Treatment of mammary glands, removed from estrogen/progesterone-primed C57Bl/6J mice and maintained in organ culture, with TCDF suppressed lobule development (greater than twofold decreases in lobule number and size), with a concomitant suppression of DNA synthesis, as judged by a 35 to 45% decrease in [3H]thymidine incorporation in the TEBs. Immunohistochemical staining patterns for AHR, aryl hydrocarbon nuclear translocator (ARNT; the heterodimerization partner of AHR), and two AHR-regulated genes, Cyp1A1 and Cyp1B1, were similar and not altered by treatment of mammary glands in organ culture with TCDF. The observed differences in the development of mammary glands from AHR +/+ and -/- mice, associated expression of the AHR protein with hormone-dependent lobule development, and suppressive actions of TCDF support the position that, in C57Bl/6J mice, development of the mammary gland is at least in part AHR dependent. Development occurs in the absence of exogenous AHR ligand, suggesting that the unoccupied receptor may function to support the proliferative stages required for full lobule development.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Benzofurans; Cell Division; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; Cytochrome P-450 Enzyme System; DNA Replication; Epithelial Cells; Female; Gene Expression; Immunoenzyme Techniques; Mammary Glands, Animal; Mice; Mice, Inbred C57BL; Mice, Knockout; Organ Culture Techniques; Receptors, Aryl Hydrocarbon; RNA, Messenger; Signal Transduction

The metabolic degradation of fluorinated, chlorinated-fluorinated and chlorinated congeners was measured in liver homogenate of NMRI mice. While in the time period between 0 and 240 min no degradation of the 2,3,7,8-TCDD/TCDF could be detected, for all fluorinated congeners a perceptible degradation was found, even for the 2,3,7,8-TFDD. Stepwise chlorination of the 2,3,7,8-fluorinated congeners leads to a decrease of the degradation rate. In the EROD test, the exchange of chloro- with fluorosubstituents in the 2,3,7,8-TCDF leads to a decrease of induction potency. 3,7-Dichloro-2,8-difluorodibenzofuran was about 1/1000th as potent as 2,3,7,8-TCDF, while 2,3,7,8-TFDF was complete inactive. Comparison of the metabolic rates of different TCDD with those of the analogous TFDD demonstrates that the order of enzymatic degradation of different TCDD and the analogous TFDD is identical. The TFDD are degraded slightly faster than the corresponding TCDD. Surprisingly 1,4,6,9-TXDD showed the second slowest metabolic rate of the fluorinated and chlorinated TXDD after 2,3,7,8-TXDD although none of the 2,3,7,8-positions were substituted. Judging from 2,3,7,8-TFDD and 1,7-dichloro-2,8-difluorodibenzofuran the metabolic pathway of fluorinated and chlorinated-fluorinated congeners seem to be comparable to the chlorinated congeners.

Topics: Animals; Benzofurans; Biotransformation; Cytochrome P-450 CYP1A1; Dioxins; Liver; Male; Mass Spectrometry; Mice; Polychlorinated Dibenzodioxins; Soil Pollutants; Structure-Activity Relationship

Concentration-dependent induction of cytochrome P4501A (CYP1A) and intracellular porphyrin accumulation were observed following treatment of chicken embryo hepatocyte (CEH) cultures with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4'-tetrachlorobiphenyl (PCB 77, IUPAC nomenclature), 2,3',4,4',5-pentachlorobiphenyl (PCB 118), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169), and a commercial mixture of PCBs (Aroclor 1254). For these halogenated aromatic hydrocarbons (HAHs), or mixture, maximal CYP1A activity [measured as ethoxyresorufin-O-deethylase (EROD) activity] and immunodetectable protein were observed at concentrations just prior to, or coincident with, the concentrations at which porphyrin accumulation became evident. Both immunodetectable CYP1A protein and catalytic activity decreased at high concentrations of these compounds, but the rate and extent of decrease of immunodetectable CYP1A protein varied. Time-course studies with PCB 77 indicated a decrease in potency and an increase in maximal CYP1A induction between 24 and 48 hr of exposure which may indicate in vitro metabolism of this HAH. Intracellular accumulation of total porphyrins without CYP1A induction, was observed for 2,2',5,5'-tetrachlorobiphenyl (PCB 52), 2,2',6,6'-tetrachlorobiphenyl (PCB 54), 2,2',3,5',6-pentachlorobiphenyl (PCB 95), 2,2',4,5,5'-pentachlorobiphenyl (PCB 101), 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136), and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153). Overall, these results are consistent with a role for CYP1A induction and/or Ah receptor activation in porphyrin accumulation mediated by HAHs with a planar configuration, whereas those that are not planar may mediate porphyrin accumulation by a mechanism not involving induction of CYP1A.

Topics: Animals; Benzofurans; Cells, Cultured; Chick Embryo; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Enzyme Induction; Liver; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Porphyrins

In vitro induction of ethoxyresorufin O-deethylase (EROD) activity in cell cultures is an extensively validated tool for measuring overall potencies of mixtures of halogenated aromatic hydrocarbons (HAHs) in samples from the abiotic or biotic environment. For risk assessment with special attention to effects in wild birds, an assay was developed that makes use of chicken embryo hepatocytes. However, it was questioned whether compound-specific responses are consistent at the various developmental stages. The results of our present study show that there are considerable differences between early and late embryonal and post-hatching stages. The induction of EROD was measured in primary chicken hepatocyte cultures. The cells were isolated at day 14 and day 19 of embryonal development and at day 1 post hatching. Hepatocytes were exposed in vitro to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB 126, IUPAC nomenclature) and 2,3',4,4',5-pentachlorobiphenyl (PCB 118). The respective compounds were chosen as representatives for dioxins, furans, non-ortho PCBs, and mono-ortho PCBs. These groups of chemicals have been identified as environmental contaminants with major dioxin-like effects that are mediated by a common receptor, the arylhydrocarbon (Ah) receptor. At all developmental stages, TCDF was more potent than TCDD. Relative potencies (RP = EC50TCDD/EC50HAH) decreased in the order TCDF < TCDD < PCB 126 < PCB 118. Depending on the developmental stage, TCDF was 1.2 to 3.4 times more potent than TCDD. PCB 126 was equipotent or less potent by a factor of 3 than TCDD. PCB 118 was 100 to 300 times less potent than TCDD. Both the mean effective concentration (EC50) and the maximum EROD activity (Ymax) of all compounds were lower in hepatocyte cultures from 14-day-old embryos than those from 19-day-old embryos or 1-day-old hatchlings. RPs were comparable in 19-day-old embryos and in hatchlings, but significantly different in 14-day-old embryos.

Topics: Animals; Animals, Newborn; Benzofurans; Cells, Cultured; Chick Embryo; Chickens; Cytochrome P-450 CYP1A1; Enzyme Induction; Liver; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins

Interaction between toxic compounds has long been known to researchers. Attempts to model this interaction have been based on two basic paradigms--termed additivity and independence (1, 2). Previous models based on these assumptions focused on measuring the interaction between the compounds and then classifying the type of interaction as synergism, antagonism, additivity or independence (3, 4). The aim of this work is to present a generalization of the independent action hypothesis that is quantitatively capable of describing deviations regardless of the underlying single component dose response models. The mathematical framework of copulas is employed. This approach is then tested against data sets with both human health and ecological risk applications.

Topics: Animals; Benzofurans; Cleft Palate; Data Interpretation, Statistical; Drug Antagonism; Drug Interactions; Drug Synergism; Drug-Related Side Effects and Adverse Reactions; Humans; Hydrocarbons, Chlorinated; Insecticides; Mice; Mice, Inbred C57BL; Models, Theoretical; Polychlorinated Dibenzodioxins

Insulin stimulated proliferation of MCF-7 human breast cancer cells in serum-free medium, whereas 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) did not affect cell growth. In cells cotreated with insulin plus TCDD or TCDF, insulin-induced cell proliferation and [3H]thymidine incorporation were inhibited. In contrast, alpha-naphthoflavone, a partial aryl hydrocarbon (Ah) receptor antagonist, blocked the inhibitory effects of TCDD, suggesting that the Ah receptor was involved in TCDD-induced responses in MCF-7 cells. TCDD alone did not affect Kd and Bmax values for binding of [125I]insulin to the insulin receptor (IR); however, in MCF-7 cells cotreated with insulin plus TCDD, the insulin-induced Kd value for IR-ligand binding was decreased and the Bmax value was increased. TCDD induced IR mRNA levels and inhibited several other insulin-induced responses including c-fos protooncogene expression, phosphorylation of the insulin receptor, and a 185-kDa protein in MCF-7 cells.

Topics: Base Sequence; Benzofurans; Breast Neoplasms; Carcinoma; Cell Division; Humans; Insulin Antagonists; Molecular Sequence Data; Polychlorinated Dibenzodioxins; Tumor Cells, Cultured

The disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran (TCDF) was investigated in rainbow trout (Oncorhynchus mykiss) in order to better understand the metabolic and physiological factors that modulate the fate of this extremely toxic compound in rainbow trout compared to other species. The fish were dosed orally with [3H]TCDF (1 microgram/kg); fish were terminated at 1-19 days for the determination of whole body half-life or at 0.3-28 days for determination of tissue distribution. Unassimilated TCDF (51.5% of the dose) was eliminated with a half-life of 0.84 days. The assimilated body burden of TCDF equivalents decreased with a half-life of 14.8 days (determined between 3 and 19 days). Trout muscle showed a relatively high capacity to accumulate and retain (unmetabolized) TCDF, accounting, at 3 days, for 32% of the body burden of TCDF equivalents (half-life in muscle, 15.2 days). Trout liver, on the other hand, showed a relatively low capacity to accumulate and metabolize TCDF. At 3 days, the concentrations of TCDF equivalents in liver and bile were, respectively, 0.37 ng/g liver (0.88% of the body burden) and 4.8 ng/ml bile. The data suggest that the relatively high affinity of lipid-rich trout muscle for TCDF limits the ability of the liver to accumulate and metabolize TCDF. The major TCDF metabolites found in trout liver and bile were, respectively, 4-OH-TCDF and TCDF-4-O-glucuronide.

Topics: Animals; Benzofurans; Bile; Chromatography, High Pressure Liquid; Environmental Pollutants; Half-Life; Liver; Muscles; Oncorhynchus mykiss; Tissue Distribution

The disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran (TCDF) was was investigated in channel catfish (Ictalurus punctatus) in order to better understand the metabolic and physiological factors that modulate the fate of this extremely toxic compound in channel catfish compared to other species. The fish were dosed orally with [3H]TCDF (1 microgram/kg); tissue were harvested at 3, 7, and 14 days for radioassay. The body burden of TCDF equivalents in catfish at 3 days was 0.36 microgram/kg, which was decreasing with a half-life of 3.6 days. Catfish muscle showed a relatively low capacity to accumulate and retain TCDF, accounting, at 3 days, for only 19.0% of the body burden of TCDF equivalents (half-life in muscle, 5.0 days). Catfish liver, on the other hand, showed a high capacity to accumulate and metabolize TCDF and to secrete TCDF metabolites into the bile. At 3 days, the concentrations of TCDF equivalents in liver and bile were, respectively, 5.7 ng/g liver (19% of the body burden) and 129 ng/ml bile. However, the concentration of TCDF equivalents in liver decreased with a half-life of 1.8 days to 0.04 ng/g (2.0% of the body burden) at 14 days. Thus, the capacity of catfish liver to retain TCDF decreased dramatically as the body burden decreased. The data suggest that the low affinity of lipid poor catfish muscle for TCDF may allow catfish liver to accumulate a concentration of TCDF sufficient to induce the metabolism of this compound by liver monooxygenases. The major TCDF metabolites found in catfish liver and bile were, respectively, 4-OH-TCDF and TCDF-4-O-glucuronide.

Topics: Animals; Benzofurans; Bile; Environmental Pollutants; Half-Life; Ictaluridae; Liver; Tissue Distribution

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and benz[a]anthracene (BA) highly induce cytochrome P4501A1, determined by aryl hydrocarbon hydroxylase (AHH) activity, in human hepatoma HepG2 cells within 24 h. AHH activity induced by TCDD and TCDF persists for at least 48 h. In contrast, AHH activity induced by BA rapidly declines, although the amounts applied are 4-5 orders of magnitude higher than those of TCDD or TCDF. AHH induction in HepG2 cells differs from that in rat hepatoma cells H4IIEC3/T in two aspects: (1) HepG2 cells are 20 times less sensitive to the test compounds than H4IIEC3/T cells. (2) TCDF-induced AHH activity does not persist in the rat cells. The results suggest that human HepG2 cells, because of their low sensitivity, are inferior to rat H4IIEC3/T cells for determining TCDD equivalents in environmental samples. They may be useful for investigating species dependent differences in the toxicokinetics of individual polyhalogenated aromatic hydrocarbon congeners.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Benz(a)Anthracenes; Benzofurans; Biological Assay; Carcinoma, Hepatocellular; Cytochrome P-450 CYP1A1; Environmental Pollutants; Humans; Liver Neoplasms; Polychlorinated Dibenzodioxins; Rats; Tumor Cells, Cultured

The basic helix-loop-helix containing dioxin receptor mediates dioxin signal transduction. The ligand-activated receptor complex binds to specific sequences termed xenobiotic response elements and regulates transcription of target genes such as the gene for cytochrome P450IA1. This study demonstrates that induction of cytochrome P450IA1 and P450IB1 gene expression by a dioxin receptor ligand is repressed by camptothecin, an inhibitor of the topoisomerase I enzyme. However, a transiently transfected reporter construct under control of an xenobiotic response element-containing promoter was not affected by the topoisomerase inhibitor. In agreement with this observation, ligand-dependent activation of the dioxin receptor to its DNA-binding form is not altered by camptothecin as analyzed by electrophoretic mobility shift assay. Moreover, the inhibitory effect of camptothecin cannot be exerted once the P450IA1 gene has been activated. These results imply that topoisomerase I activity is necessary for the primary P450IA1 induction response, possibly involving dioxin-dependent alterations in chromatin structure of the P450IA1 promoter.

Topics: Adult; Base Sequence; Benzofurans; Blotting, Northern; Camptothecin; Cytochrome P-450 Enzyme System; DNA Topoisomerases, Type I; Enzyme Induction; Enzyme Inhibitors; Gene Expression; Gene Expression Regulation; Humans; Keratinocytes; Molecular Sequence Data; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; RNA, Messenger; Topoisomerase I Inhibitors; Transfection

Studies were conducted to examine the effects of benzo[a]pyrene (BaP) and related-aromatic hydrocarbons (AHs) on the DNA synthetic profiles of adult rat hepatocytes in primary culture. Scheduled DNA synthesis in control cultures peaked at 64 h and was negligible by 72 h after initial seeding of freshly isolated hepatocytes. A concentration-dependent inhibition of DNA synthesis was observed in 1-day old hepatocyte cultures treated with BaP (0.3-30 microM) for up to 28 h. Comparable inhibitory responses were observed in cultures treated for 24 h with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 0.01-1 nM) or 2,3,7,8-tetrachlorodibenzofuran (TCDF, 0.01-1 nM), but not in cultures treated with perylene (0.01-100 nM) or benzo[e])pyrene (1-1000 nM). Ethoxyresorufin-O-deethylase (EROD) activity was highly inducible in hepatocytes challenged for 24 h with BaP (0.3-3 microM) or TCDD (0.1-100 nM) with peak induction observed at 12 or 36 h after chemical challenge, respectively. To determine if DNA synthesis inhibition by these agents involved aryl hydrocarbon receptor (AhR)-related events, subsequent experiments were conducted to examine the interactions of alpha-naphthoflavone (alpha-NF) and ellipticine (ET) with BaP and TCDD in this cell system. Pretreatment with alpha-NF (10 nM) for 24 h prevented the inhibitory effects of both BaP (3 microM) and TCDD (1 nM), while ET (0.01 nM) pretreatment selectively antagonized the effects of BaP (3 microM). Pretreatment of hepatocytes with TCDD or TCDF (1 nM) for 24 h before the onset of DNA synthesis followed by challenge with BaP (3 microM) partially antagonized the inhibitory response to BaP. These data implicate AhR-related signal transduction in the inhibition of hepatocyte DNA synthesis by BaP and related AHs and suggest that in the case of BaP, metabolism by cytochrome P450 to toxic intermediates contributes to the inhibitory response.

Topics: Analysis of Variance; Animals; Benzo(a)pyrene; Benzofurans; Cells, Cultured; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; DNA; Dose-Response Relationship, Drug; Female; Flow Cytometry; Hydrocarbons; L-Lactate Dehydrogenase; Liver; Oxidoreductases; Polychlorinated Dibenzodioxins; Rats; Rats, Sprague-Dawley; Receptors, Aryl Hydrocarbon

Polychlorinated dibenzo-p-dioxins and dibenzofurans induce exthoxyresorufin-O-deethylase (EROD) activity, a marker for CYP1A1. Differences in potency of these compounds can be attributed to differences in their affinity for the Ah receptor as well as differences in pharmacokinetics. To test the role of pharmacokinetics in the in vivo potency of these chemicals, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) were administered to female B6C3F1 mice for 4 or 13 weeks of treatment and EROD activity in liver and skin was determined. The doses were designed to be equally potent based on the published Toxic Equivalency Factor (TEF) values for these compounds. Mice received either 150 ng TCDD/kg/day or 1500 ng TCDF/kg/day, 5 days/week for either 4 or 13 weeks. At 4 weeks, hepatic EROD was induced 11- and 7-fold by TCDD and TCDF, respectively. These data indicate that the published TEFs accurately estimated the relative potency of TCDF after 4 weeks of treatment. After 13 weeks, hepatic EROD was induced 41- and 6-fold by TCDD and TCDF, respectively. The TEFs did not accurately estimate the relative inductive potency of these compounds when compared after 13 weeks of treatment. The inability of the TEFs to predict the relative potency of these compounds after 13 weeks of treatment may be due in part to the differences in the pharmacokinetic properties of each congener. The half-life of TCDF and TCDD is approximately 2 and 15 days, respectively. Steady-state levels of TCDD were not attained by 4 weeks, which is reflected in the increase in hepatic EROD between 4 and 13 weeks. In contrast, steady-state levels of TCDF were reached within 4 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzofurans; Body Weight; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Drug Administration Schedule; Enzyme Induction; Female; Half-Life; Mice; Mice, Inbred Strains; Organ Size; Oxidoreductases; Polychlorinated Dibenzodioxins; Sensitivity and Specificity; Skin

Treatment of B6C3F1 mice with acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene and dibenzofuran resulted in induction of hepatic microsomal methoxyresorufin O-deethylase (MROD) activity. Acenaphthylene was the most potent inducer of MROD, a Cyp1a2-dependent activity, and was utilized as a prototypical inducer for this group of tricyclic hydrocarbons. Acenaphthylene (300 mg/kg) caused a > 80-fold induction of hepatic microsomal MROD activity; no induction was observed in kidney or lung. Analysis of induced hepatic microsomes with antibodies to Cyp1a1 and Cyp1a2 showed that acenaphthylene induced immunoreactive Cyp1a2 but not Cyp1a1 proteins and subsequent mRNA analysis confirmed with a cDNA probe for Cyp1a1 and Cyp1a2 that acenaphthylene induced Cyp1a2 but not Cyp1a1 mRNA. Results from nuclear run-on experiments using hepatic nuclei showed that acenaphthylene caused an approximately 4-fold increase in the rate of Cyp1a2 gene transcription in B6C3F1 mice. Results of competitive binding studies indicated that the tricyclic hydrocarbons did not competitively displace [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin or [3H]benzo[a]pyrene from the mouse hepatic cytosolic aryl hydrocarbon (Ah) receptor or 4S carcinogen binding protein respectively. The data indicate that acenaphthylene and related tricyclic hydrocarbons induce Cyp1a2 gene expression in B6C3F1 mice via an Ah receptor-independent pathway. Thus, tricyclic hydrocarbons induce Cyp1a2 without the co-induction of Cyp1a1 and therefore these relatively non-toxic compounds can be used to further probe the role of Cyp1a2 in the metabolism and metabolic activation of diverse chemical carcinogens.

Topics: Acenaphthenes; Animals; Anthracenes; Antibodies, Monoclonal; Benzofurans; Crosses, Genetic; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 Enzyme System; Enzyme Induction; Female; Fluorenes; Male; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Microsomes, Liver; Oxidoreductases; Perylene; Phenanthrenes; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon

Cytochrome P4501A1 (CYP1A1) is known to play important roles in the activation and detoxification of carcinogens and other toxicants in vertebrate animals, including fish. Although extensively studied in mammalian systems, the regulation of CYP1A forms in other vertebrates is less well understood. We examined the time course and dose-response relationships for induction of CYP1A1 mRNA, protein, and catalytic activity by 2,3,7,8-tetrachlorodibenzofuran (TCDF) in the marine fish Stenotomus chrysops (scup). The time course of CYP1A1 induction was determined following a single ip dose (10 nmol/kg) of 2,3,7,8-TCDF. Hepatic ethoxyresorufin O-deethylase activity was increased after 1 day, reached a maximum by 8 days, and was still elevated 14 days after treatment. The content of immunodetectable CYP1A1 protein in liver was elevated on Day 1 and continued to increase through 14 days. CYP1A1 protein content was also strongly induced in heart and gill beginning at 2 days after treatment and extending through Day 14. Hepatic CYP1A1 mRNA was strongly induced by 1 day after dosing and remained elevated through 14 days. The sustained induction of CYP1A1 mRNA by 2,3,7,8-TCDF contrasts with the transient induction seen previously in fish treated with nonhalogenated inducers and most likely reflects differences in persistence of the inducers. Dose-response studies indicated that induction of CYP1A1 mRNA, protein, and catalytic activity occurred following doses of 2,3,7,8-TCDF as low as 0.4 nmol/kg (120 ng/kg), within the range of whole-body contents of this congener measured in fish from contaminated environments. The estimated dose producing half-maximal CYP1A1 induction in scup was approximately 2-10 nmol/kg, suggesting that the sensitivity of these fish to induction may be as great as or greater than that of rats. In contrast to previous results obtained with 3,3',4,4'-tetrachlorobiphenyl (TCB) and beta-naphthoflavone, which appear to inhibit or inactivate CYP1A1 in fish and other vertebrates, there was a good correlation among levels of CYP1A1 mRNA, protein, and catalytic activity in individual fish following various doses of 2,3,7,8-TCDF. The difference in response to 2,3,7,8-TCDF versus 3,3',4,4'-TCB may reflect differences in the inducing potencies of the two compounds relative to their similar potencies as inhibitors of CYP1A1 catalytic activity. In additional studies to evaluate structure-activity relationships for CYP1A1 induction by chlorinated dibenzofurans in

Topics: Animals; Benzofurans; Catalysis; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; DNA, Complementary; Dose-Response Relationship, Drug; Enzyme Induction; Female; Fishes; Isomerism; Male; Oxidoreductases; RNA, Messenger; Structure-Activity Relationship; Time Factors

The pharmacokinetics of TCDD and related compounds is congener, dose, and species specific, with urinary and biliary excretion being dependent on the metabolism of these compounds. Isolated hepatocytes and liver slices in suspension culture and hepatic microsomes were used as in vitro models to assess the hepatic uptake and metabolism of [3H]- and [14C]TCDD and [3H]TCDF (0.01-1.0 microM) in control and induced (5 micrograms TCDD/kg, 3 days earlier) male Sprague-Dawley rats. TCDD pretreatment, with an increase in cytochromes P450 1A1 and 1A2 (CYP1A1, CYP1A2), produced an increase in the hepatic uptake of TCDD, while no increase in the hepatic uptake of TCDF was observed. The results are consistent with CYP1A2 serving as a hepatic binding protein for TCDD but not for TCDF. The rates of metabolism of TCDD and TCDF were directly proportional to their concentrations, indicating that the reaction follows first order kinetics at concentrations from 0.01 to 1.0 microM. Very limited metabolism of TCDD and TCDF was observed in control rat liver (0.45 and 3.2 pmol/hr/g hepatocyte wet wt at 0.1 microM, respectively). TCDD induced its own rate of metabolism about two- to fivefold at 1.0 microM but no induction was observed at 0.01 and 0.1 microM. In contrast, TCDD markedly induced the rate of TCDF metabolism at all substrate concentrations. While the results support the role of rat CYP1A1 in TCDF metabolism, the data suggest that CYP1A1 or CYP1A2 may not metabolize TCDD. These results also support the hypothesis that the more rapid metabolism and excretion of TCDF accounts for the relative resistance of the rat to the acute toxicity of TCDF. Comparative studies in rat and human liver microsomes found that TCDF metabolism exhibited first order kinetics in both species. Furthermore, the rate of TCDF metabolism in human liver microsomes was similar to that of control rat liver microsomes. Together the results suggest that TCDF will be far more persistent in rats, and possibly humans, following exposure at low doses which do not significantly induce cytochrome P450 1A1 and/or 1A2.

Topics: Animals; Benzofurans; Cytochrome P-450 Enzyme System; Humans; In Vitro Techniques; Liver; Male; Microsomes, Liver; Polychlorinated Dibenzodioxins; Rats; Rats, Sprague-Dawley

Topics: Animals; Benzofurans; Body Weight; Brachyura; Fisheries; Gas Chromatography-Mass Spectrometry; Liver; Marine Biology; Muscles; Nephropidae; New Jersey; New York; Pancreas; Polychlorinated Dibenzodioxins; Water Pollutants, Chemical

Previous studies have established that TCDF is rapidly metabolized and excreted in rats and that pretreatment of rats with TCDD increases the rate of hepatic metabolism of this compound. The extrahepatic metabolism of TCDF was investigated to assess which enzyme was involved in the metabolism of this compound. Very little metabolism of TCDF was detected in control microsomes (0.3-3.0 pmol/mg/hr), while TCDF metabolism was increased 40- to 200-fold in TCDD-induced rat liver, kidney, and lung microsomes. Since TCDD induces cytochrome P4501A1 and P4501A2 (CYP1A1 and CYP1A2) in the rat liver but only CYP1A1 in kidney and lung, these results suggest that CYP1A1 metabolizes TCDF. To test this hypothesis, TCDF metabolism was investigated in the presence and absence of selective chemical inhibitors and antibodies to CYP1A1 and 1A2. 1-Ethynylpyrene, a suicide inhibitor of CYP1A1 and antibody to rat CYP1A1, produced a dose-dependent inhibition of TCDF metabolism in TCDD-induced rat liver microsomes. Conversely, 2-ethynylnaphthalene, a suicide inhibitor of CYP1A2 and antibody to rat CYP1A2, had no inhibitory effect on the hepatic microsomal metabolism of TCDF. Together, the results strongly indicate that rat CYP1A1 is the primary enzyme responsible for the metabolism of TCDF. 4-Hydroxy-2,3,7,8-TCDF was also identified as the major TCDF metabolite formed by rat CYP1A1. TCDF was also metabolized by human liver microsomes and recombinant yeast microsomes expressing human CYP1A1 and reductase but not by yeast microsomes expressing human CYP1A2 with or without reductase. A similar HPLC profile of TCDF metabolites was observed with microsomes from human liver and yeast expressing human CYP1A1. However, based on ethoxyresorufin-O-deethylase activity, a marker of CYP1A1, the relative rate of TCDF metabolism is about 100-fold greater in TCDD-induced rat liver microsomes than in yeast microsomes expressing human CYP1A1 and reductase. Thus, although TCDF is metabolized by rat and human CYP1A1, the results indicate that there are marked quantitative differences in metabolism which suggest that TCDF will be more persistent in humans.

Topics: Animals; Benzofurans; Cytochrome P-450 CYP1A2; Cytochrome P-450 Enzyme System; Environmental Pollutants; Humans; Liver; Male; Oxidoreductases; Rats; Rats, Sprague-Dawley; Species Specificity

The laterally halogenated chemicals 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 3,3',4,4'-tetrachlorobiphenyl (TCB) exhibit the same spectrum of toxic effects as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototype and most toxic member of the halogenated aromatic hydrocarbon family. Metabolism of all three compounds appears to be the rate-limiting step for excretion, which is primarily via the bile into the feces. Therefore, the biliary elimination of TCDF, TCDD, and TCB was examined as an indirect measure of metabolism. Male F344 rats were anesthetized with pentobarbital, the bile duct was cannulated, and 0.1 mumol [3H]TCDD, [14C]TCDF, or [14C]TCB/kg body wt was administered iv. Bile was collected for 0-8 hr while the animals were kept under anesthesia. To determine if TCDF was able to induce its own metabolism in vivo, a single dose of 1.0 mumol TCDF/kg was administered to rats by oral gavage 3 days prior to iv injection of 0.1 or 0.3 mumol [14C]TCDF/kg. Biliary excretion and hepatic concentrations of [14C]TCDF were significantly increased in the pretreated animals. These results suggest an autoinduction of TCDF metabolism. Essentially all biliary [14C]TCDF radioactivity was attributable to metabolites. High-pressure liquid chromatography profiles of biliary radioactivity from 0 to 4 hr were qualitatively different between naive and pretreated rats. To determine if pretreatment with TCDD altered the metabolism of TCDF and vice versa, a single dose of 1.0 mumol TCDF/kg or 0.1 mumol TCDD/kg was administered by oral gavage 3 days prior to iv injection of 0.1 mumol [3H]TCDD or [14C]TCDF/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Aroclors; Benzofurans; Bile; Chlorodiphenyl (54% Chlorine); Enzyme Induction; Feces; Male; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Rats; Rats, Inbred F344

The distribution of 2,3,7,8-tetrachloro-[3H]dibenzofuran ([3H]TCDF; 40 micrograms/kg) resembled that earlier reported for 2,3,7,8-tetrachlorodibenzo-p-dioxin, with a strong accumulation in the liver and a selective uptake in the nasal olfactory mucosa of adult and fetal mice. Pretreatments with a series of selected congeners of polychlorinated biphenyls (PCBs), i.e.. I (IUPAC)-77, I-105, I-118, I-126, I-153, I-156, I-169, and a commercial preparation, Aroclor 1254 (25-100 mg/kg body wt. i.p.), were found to modulate the hepatic uptake of [3H]TCDF (24 h post-3H-injection). At a short pretreatment time (4 h), non-ortho-chlorinated congeners decreased the uptake of [3H]TCDF equivalents in the liver (e.g., I-126 = 3,3',4,4',5-pentachlorobiphenyl: 34% of control), while several mono- and di-ortho PCB congeners and Aroclor 1254 increased the hepatic uptake of [3H]TCDF (e.g., I-156 = 2,3,3',4,4',5-hexachlorobiphenyl: 183% of control). At a longer pretreatment time (48 h), both a non-ortho (I-169 = 3,3',4,4',5,5'-hexachlorobiphenyl) and mono-ortho PCB congener(s) (e.g. I-156) markedly increased the hepatic 3H-uptake (190%), a probable effect of an induction of hepatic binding sites for TCDF. Ethoxyresorufin-O-deethylase activities, regarded to mirror the metabolic activity of cytochrome P-450 IA1 (CYP IA1), were strongly and time-dependently induced after I-169, but not after I-156, pretreatment (25 mg/kg). The initial liver concentrations of the two PCB congeners were similar and increased for I-169 but not for I-156 at later time points. In conclusion, the results show a selective uptake of [3H]TCDF in the mouse liver and nasal olfactory mucosa of both dam and fetus. The uptake of [3H]TCDF in the liver is influenced both by dose and pre-exposure with PCBs. The presence of a PCB-sensitive, but CYP IA1-independent, hepatic binding site for TCDF is suggested. Consequently, pharmacokinetic interactions with PCBs complicate the toxicity assessment of TCDF in complex mixtures.

Topics: Animals; Aroclors; Autoradiography; Benzofurans; Chlorodiphenyl (54% Chlorine); Chromatography, Gas; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Drug Interactions; Female; Liver; Mice; Oxidoreductases; Polychlorinated Biphenyls; Pregnancy; Tissue Distribution

Polychlorinated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzofuran (TCDF) have been shown to induce transcription of the cytochrome P-450IA1 gene by activating an intracellular receptor protein (the Ah- or dioxin receptor) to bind to specific DNA sequences, termed xenobiotic response elements (XREs). However, the expression and inducibility of the cytochrome P-450IA1 activity exhibit tissue-specific differences. With regard to the TCDF induction response, we have examined three human cell types of endodermal (the hepatoma cell line HepG2), ectodermal (normal keratinocytes), and mesodermal origin (normal fibroblasts). DNase I hypersensitivity analysis of the 5' flank and first intron of the P-450IA1 gene showed that in the nonresponsive fibroblasts the chromatin structure lacked open regions while in the two responsive cell types (keratinocytes and HepG2) several constitutive hypersensitive sites as well as TCDF-induced alterations in the chromatin structure could be detected. This observation might correlate with the fact that the XRE, in either the context of the P-450IA1 gene sequences or in front of a heterologous promoter, was inefficient in directing a TCDF induction response in fibroblasts. In in vitro DNA binding studies, the dioxin receptor was activated to a DNA-binding nuclear form in all three cell types. However, in fibroblast nuclear extracts two novel constitutive protein-XRE complexes were detected. The fibroblast factor(s) were immunochemically distinct from the receptor but exhibited indistinguishable DNA binding specificity. These data are compatible with a model where the P-450IA1 is noninducible in fibroblasts due to the presence of a putative repressor(s) which may compete effectively with the receptor for binding to the response element as indicated by in vitro DNA-binding off-rate experiments.

Topics: Base Sequence; Benzofurans; Cells, Cultured; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Deoxyribonuclease I; DNA; Fibroblasts; Gene Expression Regulation, Enzymologic; Humans; Keratinocytes; Molecular Sequence Data; Oxidoreductases; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Receptors, Drug; Regulatory Sequences, Nucleic Acid; RNA, Messenger; Tumor Cells, Cultured

Three dioxin-receptor ligands were analyzed for their effect on cytochrome P450IA1 mRNA expression in normal human keratinocytes. Although a 2 h pulsed treatment with the receptor agonists 2,3,7,8-tetrachlorodibenzofuran (TCDF) and beta-naphthoflavone (BNF) gave the same maximal induction response, the effect of BNF was transient compared to effect of TCDF. This was most likely due to metabolism of BNF as exemplified by the fact that a P450IA1 enzyme suicide-inhibitor, 1-ethynylpyrene, could prolong the induction response following a short BNF treatment. The TCDF induction of a reporter gene construct under the control of the -1140 to +2435 part of the CYPIA1 gene transiently transfected into HK was effectively inhibited by the dioxin-receptor antagonist alpha-naphthoflavone (ANF). In addition, ANF inhibited the accumulation of TCDF-activated nuclear receptors with capacity to bind to a xenobiotic response element. Interestingly, ANF could also suppress already maximally induced P450IA1 mRNA levels. The data demonstrate that the stability of the ligand influences the long-term effects on gene expression and that the effect of stable ligands may be masked due to receptor antagonist presence. In addition, the results support the hypothesis that a constant low level of activated nuclear receptors is required to maintain induced P450IA1 expression.

Topics: Base Sequence; Benzoflavones; Benzofurans; beta-Naphthoflavone; Cytochrome P-450 Enzyme System; Humans; Keratinocytes; Molecular Sequence Data; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Receptors, Drug; RNA, Messenger

Insulin-like growth factor-I (IGF-I) stimulated the growth and [3H]thymidine uptake in MCF-7 human breast cancer cells grown in serum- and growth factor-inactivated serum-containing media. Cotreatment of the cells with IGF-I plus 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a significant decrease in mitogen-induced cell proliferation and [3H]thymidine uptake. Similar effects were observed for cells treated with 2,3,7,8-TCDD and IGF-I plus 17 beta-estradiol. The relative antimitogenic activities of 2,3,7,8-TCDD and related compounds followed the order 2,3,7,8-TCDD greater than 2,3,7,8-tetrachlorodibenzofuran (TCDF) greater than 1,2,7,8-TCDF greater than 1,3,7,8-TCDD which was similar to their aryl hydrocarbon (Ah) receptor binding affinities. The results showed that 2,3,7,8-TCDD did not alter the IGF-I receptor mRNA levels or the KD values for binding of [125I]IGF-I to the IGF-I receptor in MCF-7 cells. However, 2,3,7,8-TCDD significantly decreased the number of IGF-I-induced IGF-I receptor binding sites and this may play a role in the growth-inhibitory properties of 2,3,7,8-TCDD and related compounds and in the 'cross-talk' between the two endocrine-response pathways.

Topics: Benzofurans; Breast Neoplasms; Cell Division; Estradiol; Humans; Insulin-Like Growth Factor I; Polychlorinated Dibenzodioxins; Receptor, IGF Type 1; Receptors, Aryl Hydrocarbon; Receptors, Drug; Tumor Cells, Cultured

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to dietary 2,3,7,8-[3H]tetrachlorodibenzofuran (TCDF) (0.36 to 42.8 ng g-1) and accumulation, tissue distribution, biotransformation, and hepatic monooxygenase enzyme (MO) induction were studied. The assimilation efficiency of TCDF ranged from 49 to 62% in 30-day exposures and was independent of the TCDF level in the diet. Depuration half-lives (whole body) of TCDF following 30-day exposure ranged from 40 to 77 days and were significantly more rapid in fish exposed to 42.8 ng g-1. Liver somatic index (LSI) and rate of increase in liver weight were elevated in fish exposed to 42.8 ng g-1 TCDF compared to controls. Exposure to 9.2 ng g-1 TCDF in the diet for 140 days also resulted in higher LSI values, as well as increased mortality (16%), but had no significant effects on growth. [3H]TCDF was found mainly in the carcass (63-74%) and GI tract (18-31%), with lesser amounts in liver (0.6-2.3%) during the 140-day exposure, primarily (> 98%) in the form of the parent compound. Radioactivity in bile was found mainly as a single polar transformation product by reverse-phase HPLC. Glucuronidase hydrolysis yielded a product with the retention time expected of hydroxylated TCDF, suggesting the presence of a glucuronide conjugate. MO enzyme induction measured by ethoxyresorufin-O-deethylase (EROD) activity in liver (postmitochondrial supernatant) was 137.5 and 15 times higher than that in control fish after 30 days dietary exposure to 42.8 and 9.2 ng g-1, respectively. EROD activities were correlated with TCDF concentrations in liver (R2 = 0.59, N = 45).

Topics: Animals; Benzofurans; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Diet; Dose-Response Relationship, Drug; Enzyme Induction; Injections, Intraperitoneal; Liver; Mixed Function Oxygenases; Organ Size; Oxidoreductases; RNA, Messenger; Tissue Distribution; Trout

Differences in expression of cytochrome P450 forms and their functions in different organs and cell types could determine the response of those cells and organs to xenobiotics. Recently, we described the cellular localization of cytochrome P450IA1 (P450E) induced in 10 organs or organ systems of the fish, Stenotomus chrysops (scup) treated with 3,3',4,4'-tetrachlorobiphenyl or with 2,3,7,8-tetrachlorodibenzofuran. (R.M. Smolowitz, M.E. Hahn, and J.J. Stegeman, Drug Metab. Dispos. 19, 113, 1991). Here we describe the presence and localization of P450IA1 in organs of scup sampled directly from an environment contaminated by chlorinated biphenyls and bibenzofurans, the outer New Bedford Harbor of Massachusetts. Western blot analysis of microsomes from selected organs (liver, kidney, gill, and heart), using monoclonal antibody 1-12-3, revealed induced levels of P450IA1 in each. The localization of P450IA1 in these and other organs was determined in sections prepared by standard histological methods and stained with MAb 1-12-3 in an indirect peroxidase labeling method. P450IA1 was detected in multiple cell types in liver, including hepatic, pancreatic, and vascular tissue. Kidney and gut also showed prominent P450IA1 levels in epithelial structures and in vascular endothelial cells. Specific staining was detected in endothelial cells, but not other cell types, in heart, gill, spleen, testis, ovary, nose, and brain. In heart, the staining was present in the endocardium of atrium and ventricle, and endothelium of the coronary vasculature and great vessels. The results demonstrate that P450IA proteins are induced in many organs of fish exposed to environmental chemicals in the wild, with patterns of cellular localization like those seen in fish experimentally treated with known inducers. The strong staining of P450IA1 in endothelial cells in all organs examined supports experimental results indicating that endothelium is a major site of P450IA1 induction. Our results indicate further that immunohistochemistry is a useful method for detecting P450 induction as a biomarker for exposure.

Topics: Animals; Benzofurans; Cytochrome P-450 Enzyme System; Dibenzofurans, Polychlorinated; Environmental Exposure; Enzyme Induction; Fishes; Immunohistochemistry; Liver; Microsomes, Liver; Polychlorinated Biphenyls; Polycyclic Compounds; Tissue Distribution; Water Pollutants, Chemical

The level of charge heterogeneity in the aryl hydrocarbon receptor (AhR) was examined by high-resolution denaturing two-dimensional (2D) gel electrophoresis. Hepa 1c1c7 cell cytosolic fraction was photoaffinity-labeled with 2-azido-3-[125I]iodo-7,8-dibromodibenzo-p-dioxin and applied to isoelectric focusing (IEF) tube gels. After optimization of focusing conditions a broad peak of radioactivity was detected in the apparent pI range of 5.2-5.7. IEF tube gels were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by visualization of the radiolabeled AhR by autoradiography; three distinct isoforms were detected. The same 2D electrophoretic isoform pattern was obtained when the AhR from Hepa 1c1c7 was photoaffinity-labeled in cell culture. BPrCl cells, a mutant line derived from Hepa 1c1c7 cells, contain an AhR that is unable to bind to DNA. Photoaffinity-labeled BPrCl cytosolic fractions were subjected to 2D gel electrophoretic analysis resulting in essentially the same molecular weight and isoform pattern as seen in Hepa 1c1c7 cytosol. This result would suggest that if a mutation is present in the BPrCl AhR it has not caused a significant change in its IEF pattern, although a small shift in the pI values was observed. Two-dimensional gel electrophoresis of photoaffinity-labeled cytosolic fractions from HeLa cells, the rat liver tumor cell line McA-RH7777, and buffalo rat thymus revealed three isoforms, essentially the same isoform pattern as in Hepa 1c1c7 cells. This would indicate that despite the considerable molecular weight polymorphism between species the level of charge heterogeneity is highly conserved.

Topics: Affinity Labels; Animals; Benzofurans; Cytoplasm; DNA; Electrophoresis, Polyacrylamide Gel; Humans; Isoelectric Focusing; Liver Neoplasms, Experimental; Molecular Weight; Neoplasm Proteins; Polychlorinated Dibenzodioxins; Rats; Rats, Inbred BUF; Receptors, Aryl Hydrocarbon; Receptors, Drug; Species Specificity; Thymus Gland; Tumor Cells, Cultured

In this study, the effects of benzo[a]pyrene (BP), 3-methylcholanthrene (3MC) and tetrachlorodibenzofuran (TCDBF) on the expression of the cytochrome P450IA1 gene in the rat hepatoma cell line H4IIE were examined. The initial rate of increase in the steady-state concentration of the mRNA for this gene was similar with each of these inducers; however, the elevated level of this mRNA was more sustained after TCDBF treatment. Nuclear run-off assays suggested that the elevated level of the mRNA was caused principally by an effect upon transcription.

Topics: Animals; Benzo(a)pyrene; Benzofurans; Cytochrome P-450 Enzyme System; Dioxins; Enzyme Induction; Gene Expression Regulation, Enzymologic; Isoenzymes; Liver Neoplasms, Experimental; Methylcholanthrene; Polychlorinated Dibenzodioxins; Rats; Tumor Cells, Cultured

The possible role of hepatic lipoproteins as intracellular carriers in the transport of 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo(a)pyrene was assessed by in vitro and in vivo studies. Following administration of [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin or unlabelled 2,3,7,8-tetrachlorodibenzofuran to C57 BL/6 mice or Sprague-Dawley rats these compounds were bound to lipoproteins which subsequently underwent rapid and pronounced degradative processing, possibly catalysed by lipoprotein lipase, to heavier entities. At the highest doses of xenobiotics administered, an almost complete disappearance of lipoprotein particles was observed. The in vitro incubation of [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin-lipoprotein and [3H]benzo(a)pyrene-lipoprotein complexes with separated Ah receptor and 4S protein, respectively, demonstrated that a passive transfer occurred; the latter was likely dependent on both the relative affinities of the ligands towards the different cellular binding components as well as on their quantitative binding capacity. Taken together, these findings support the idea of a carrier-role for lipoproteins in the intracellular transport of hydrophobic xenobiotics and it may be asked whether the widespread modulators of lipoprotein level such as fibrates or others affect drug transfer or action.

Topics: Animals; Benzo(a)pyrene; Benzofurans; Carrier Proteins; Dioxins; In Vitro Techniques; Lipoproteins; Liver; Mice; Mice, Inbred C57BL; Polychlorinated Dibenzodioxins; Rats; Rats, Inbred Strains; Receptors, Aryl Hydrocarbon; Receptors, Drug

Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) are toxic environmental contaminants which have the potential to accumulate in human tissues. In order to examine the potential for systemic exposure following dermal exposure, the absorption, distribution, and elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 1,2,3,7,8-pentachlorodibenzofuran (1PeCDF), and 2,3,4,7,8-pentachlorodibenzofuran (4PeCDF) were evaluated in male F344 rats. TCDD (0.00015, 0.001, 0.01, 0.1, 0.5, and 1.0 mumol/kg) and the three PCDFs (0.1, 0.5, and 1.0 mumol/kg) were applied to a preclipped region on the back of the rat and covered with a perforated cap. The rats were held in individual metabolism cages for 3 days. In animals administered 0.1 mumol/kg, the absorption of TCDF was greater than that of 4PeCDF, 1PeCDF, and TCDD. Relative absorption (percentage of administered dose) declined with increasing dose while the absolute absorption (microgram/kg) increased nonlinearly with dose. Absorption of TCDF at 0.1 mumol/kg was 48% of the administered dose which was significantly greater than that of the other compounds. At this dose, absorption of 4PeCDF was greater than that of TCDD. Absorption at the higher doses was similar for all four compounds. Maximum relative absorption of TCDD (approximately 40% of the administered dose) was obtained at 0.001 and 0.00015 mumol/kg. Major tissue depots for these four chemicals included liver, adipose, skin, and muscle tissue; however, the liver:fat ratio for 4PeCDF was approximately fourfold higher than that for the other three compounds. When normalized to 100% of dose absorbed, the distribution of 4PeCDF-derived radioactivity in liver and adipose tissue was similar to that previously observed after oral and iv administration. In animals administered 0.1 mumol TCDF or 1PeCDF/kg, 56 and 32% of the respective absorbed dose was excreted as polar metabolites within 3 days. Very little of the absorbed dose of either TCDD (approximately 10%) or 4PeCDF (approximately 2%) was eliminated. Results indicate that the dermal absorption of these compounds is incomplete and that systemic toxicity following acute dermal exposure to levels found in the environment is unlikely.

Topics: Administration, Cutaneous; Animals; Benzofurans; Dioxins; Dose-Response Relationship, Drug; Environmental Pollutants; Feces; Industrial Waste; Male; Polychlorinated Dibenzodioxins; Polymers; Rats; Rats, Inbred F344; Skin Absorption; Tissue Distribution

A comparison of the molecular properties of the male Long-Evans rat and male C57BL/6 mouse hepatic cytosolic aryl hydrocarbon (Ah) receptor complex was determined using 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-[3H]tetrachlorodibenzofuran (TCDF) as radioligands. In low salt buffer, the sedimentation coefficients, Stokes radii, relative molecular masses, frictional ratios, axial ratios and gel permeation chromatographic properties of the rat receptor complexes were ligand independent. In contrast, there were several ligand-dependent differences in the mouse Ah receptor complexes formed after incubation in low salt buffer and these include: sucrose density gradient analysis of the 2,3,7,8-[3H]TCDF receptor complex gave a 9.5 S specifically bound peak and a 2.6 S nonspecifically bound peak whereas the corresponding 2,3,7,8-[3H]TCDD receptor complex gave a single 9.6 S specifically bound peak; sucrose density gradient analysis of the two major peaks eluted from a Sephacryl S-300 column chromatographic separation of the 2,3,7,8-[3H]TCDF receptor complex gave two specifically bound peaks at 9.2 and 5.1 S. The molecular properties of the rat hepatic cytosolic receptor complexes incubated in high salt (0.4 M KCl) buffer were ligand independent with one exception, namely the significant difference in the sedimentation coefficient of the specifically bound disaggregated 2,3,7,8-[3H]TCDD receptor complex (6.8 S) and the corresponding 2,3,7,8-[3H]TCDF receptor complex (5.0 S). The major ligand-dependent differences in the mouse receptor complexes incubated in high salt (0.4 M KCl) were associated with the sedimentation coefficients of the complexes derived after direct incubation and after gel permeation chromatography. For example, both ligands gave two specifically bound complexes after chromatography on Sephacryl S-300 column and centrifugation of these fractions gave both the approximately 9 and approximately 5 S peaks; this suggested that there was some equilibration between the aggregated and disaggregated receptor complexes. The behavior of the 2,3,7,8-[3H]TCDF mouse receptor complex was similar after incubation in low or high salt buffer except that sucrose density gradient analysis of the gel permeation chromatographic fractions gave an additional specifically bound peak which sedimented at 7.2 S. These studies demonstrate that the molecular properties of the Ah receptor were dependent on the source of the cytosolic receptor preparation, the

Topics: Animals; Benzofurans; Centrifugation, Density Gradient; Chromatography, Gel; Cytosol; Female; Humans; Liver; Male; Mice; Mice, Inbred C57BL; Polychlorinated Dibenzodioxins; Rats; Receptors, Aryl Hydrocarbon; Receptors, Drug; Species Specificity

1,2,3,7,8-Pentachlorodibenzofuran (1PeCDF) is one of several toxic polychlorinated dibenzofurans (PCDFs) which are ubiquitous environmental contaminants. Related in structure and toxicity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), PCDFs have been detected in municipal and industrial effluents, PCB mixtures, and in a variety of antiseptics and preservative solutions. The objective of this study was to evaluate the distribution and elimination of 1PeCDF in the rat and to compare these parameters with that of 2,3,4,7,8-pentachlorodibenzofuran (4PeCDF) and 2,3,7,8-tetrachlorodibenzofuran (TCDF). After iv administration of 0.1 mumol [3H]1PeCDF/kg, 1PeCDF was rapidly cleared from the blood and distributed to the liver, muscle, skin, and adipose tissue in a manner similar to that for other dibenzofurans. The initial pool sizes of 1PeCDF-derived radioactivity in the liver, muscle, skin, and adipose tissue were 43,35,10, and 7% of the administered dose, respectively. In all cases, loss of radioactivity from these tissues could be described by exponential decay and the initial half-lives for these tissues were 1.36, 0.03, 13, and 1 day, respectively. After redistribution from the muscle, skin, and adipose tissues to the liver, 1PeCDF was metabolized to a polar metabolite(s) and excreted from the body via the bile into the feces. No parent compound was detected in the bile and fecal excretion was the major route of elimination. Most of the radioactivity in the urine was excreted within the first day, after which less than 0.5% of the dose/day was detected. More than half of the administered dose was excreted in the urine and feces within 2 days. The whole-body half-life of related compounds is 4PeCDF much greater than 1PeCDF greater than or equal to TCDF. Therefore, persistence appears to be inversely related to the metabolism of these compounds and metabolism is inhibited by chlorine-substituted carbon atoms adjacent to the oxygen atom in the dibenzofuran ring.

Topics: Animals; Benzofurans; Bile; Environmental Pollutants; Feces; Lethal Dose 50; Male; Rats; Rats, Inbred F344; Structure-Activity Relationship; Tissue Distribution

Topics: Benzofurans; Chemical Phenomena; Chemistry; Chlorine; Chromatography, Gas; Isomerism

The effects of tetrachlorodibenzofuran pretreatment was studied in microsomes from adult Drosophila of the Karsnäs 60w strain. Pretreatment for 18 h with 0.2 or 1 mg TCDBF did not increase benzo[alpha]pyrene monooxygenase activity, 7-ethyoxyresorufin deethylase activity or the formation of 2-, 3- or 4-hydroxylated metabolites from biphenyl, in accordance with previous results with alpha-naphthoflavone pretreatment. The results suggest that adult Drosophila is non-responsive to induction by polycyclic aromatic hydrocarbons. The role of the TCDD receptor, which has been reported to be present in Drosophila, is obscure against this background. The implications for mutagenicity testing in Drosophila is discussed.

Topics: Animals; Benzofurans; Cell Fractionation; Drosophila melanogaster; Environmental Pollutants; Kinetics; Microsomes; Mixed Function Oxygenases

Acute exposure of adult mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) results in a selective suppression of proliferating cells of the immune system, including hematopoietic stem cells and B cells. Suppression of B cell-mediated or humoral immunity, in turn, results in altered host resistance to the parasite Plasmodium yoelii, a malaria model. Data presented in this study demonstrate a direct effect of TCDD on cultured lymphoctes resulting in a selective inhibition of the differentiation of B cells into antibody-secreting cells. A structure-activity study suggested that this inhibition was mediated by the Ah receptor. As previously defined by receptor binding studies in hepatic cytosol, active congeners were inhibitory, whereas inactive congeners were without effect. Using lymphocytes from congenic mice which differ only at the Ah locus, it was determined that the Ahbb-derived cells were inhibited by TCDD in vitro, whereas the Ahdd-derived cells were not. B cell differentiation thus provides a valuable model for understanding TCDD toxicity as well as the role of the Ah receptor in growth and differentiation.

Topics: Animals; Antibody Formation; B-Lymphocytes; Benzofurans; Cell Differentiation; Dioxins; Female; Malaria; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Polychlorinated Dibenzodioxins; Structure-Activity Relationship; Thymectomy

The risk of cancer to humans exposed to soil treated with wastewater/sewage treatment plant sludge, known to be contaminated with small amounts of polychlorinated dibenzodioxins and dibenzofurans (PCDDs and PCDFs), was evaluated. The particulate-bound PCDDs and PCDFs are found in trace amounts in the effluent from ground water pumping (dewatering) at an abandoned wood preservation facility. The water, which was sent to a water recovery plant, underwent primary and secondary treatment prior to discharge. The residual sludge was added to agricultural soil as a conditioner. The present analysis treats the extreme case of sludge applied near the home of a target individual, a lifetime resident, who is also a farm worker in the area of the application. The successive stages of infancy, childhood and adulthood are treated separately to assess the contributions of typical age-specific indoor and outdoor activities on exposure rates. Five toxicity rating schemes using so-called TCDD equivalents, and two unit risk slopes are applied to the chemical profile in sludge to determine the cancer potency of the soil contaminants. These risk estimates range from 1 X 10-8 to 3 X 10-7.

Topics: Adult; Benzofurans; Child; Dioxins; Health; Humans; Polychlorinated Dibenzodioxins; Risk; Sewage; Skin Absorption; Soil Pollutants

A 4-S protein which specifically binds [3H]benzo(a)pyrene and other polycyclic aromatic hydrocarbons has been investigated in the rat using a hydroxylapatite assay and sucrose gradient analysis. Although there was significant interanimal variation, the specific polycyclic aromatic hydrocarbon binding activity appeared to be highest in 4-week-old male rats and declined with age. The specific [3H]benzo(a)pyrene binding activity was induced after pretreatment with either phenobarbital or isosafrole as evidenced by a 72 and 61% increase, respectively, over untreated controls. No apparent increase in specific binding activity was observed after pretreatment of animals with 3-methylcholanthrene. Pretreatment with either phenobarbital or isosafrole also resulted in the appearance of a small, nonspecific, benzo(a)pyrene binding peak at the 8- to 9-S region in the sucrose density gradients. This 8-S peak was not seen in untreated control animals and represented low affinity, high capacity binding sites. In contrast to the 8-S protein, the 4-S binding protein had low affinity for polychlorinated aromatic compounds such as tetrachlorodibenzodioxin and tetrachlorodibenzofuran. The addition of a 200-fold excess of tetrachlorodibenzofuran to incubations did not displace [3H]benzo(a)pyrene from the 4-S protein. The addition of sodium molybdate to isolation buffers, known to stabilize certain hormone receptors, did not alter the sedimentation coefficient or the specific binding activity of the 4-S protein. These experiments indicate that the 4-S protein does not appear to be a subunit of the 8-S protein. We conclude that in the rat the 4-S protein is distinct from the 8-S protein and the 4-S species may regulate the polycyclic aromatic hydrocarbon-induced expression of aryl hydrocarbon hydroxylase activity.

Topics: Age Factors; Animals; Benzo(a)pyrene; Benzofurans; Binding, Competitive; Carrier Proteins; Cytosol; Enzyme Induction; Female; Liver; Macromolecular Substances; Male; Molybdenum; Phenobarbital; Polycyclic Compounds; Rats; Safrole

Topics: Animals; Benzofurans; Biological Availability; Carbon; Coal Ash; Cyprinidae; Dioxins; Furans; Goldfish; Mass Spectrometry; Particulate Matter; Polychlorinated Dibenzodioxins; Stereoisomerism; Water Pollutants; Water Pollutants, Chemical

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) cause the same spectrum of fetal anomalies in C57BL/6N mice. Pregnant dams were treated with TCDD, TCDF and combinations of the 2 compounds on gestation day 10, and examined for maternal and fetal effects on day 18. The fetal kidneys were the most sensitive target for teratogenicity. The dose response for cleft palate induction fit the probit model for both compounds, suggesting that TCDD was approximately 30 times more potent than TCDF. The interaction between these 2 compounds was consistent with a model for additive toxicity.

Topics: Animals; Benzofurans; Body Weight; Cleft Palate; Dioxins; Dose-Response Relationship, Drug; Drug Interactions; Female; Hydronephrosis; Liver; Mice; Mice, Inbred C57BL; Organ Size; Polychlorinated Dibenzodioxins; Pregnancy; Teratogens

Topics: Animals; Benzofurans; Enzyme Induction; Male; Microsomes, Liver; Rats; Rats, Inbred Strains

The distribution and excretion of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlordibenzofuran (TCDF) were studied in pregnant C57BL/6N mice following an oral dose of 30 micrograms/kg 14C-TCDD and 800 micrograms/kg 14C-TCDF on gestation day 11. The distribution in maternal blood and liver and excretion in urine and feces was similar to that previously reported in males of the same strain. However, the rates of elimination were more rapid in pregnant females for both chemicals. This was more pronounced for TCDD than for TCDF. At all time points examined, the levels of radioactivity in the individual embryos were below 0.5% of the total TCDD dose and below 0.05% of the total TCDF dose. Assuming that all radioactive material found in embryos was unmetabolized compound, no more than 2.6 ng (8 pmoles) TCDD and 6.4 ng (21 pmoles) TCDF per g tissue were detected. In light of recent findings which strongly suggest a direct effect of TCDD and related compounds on embryonic palatal tissue, our data clearly support the potent teratogenic effect of TCDD and TCDF on the development of the secondary palate.

Topics: Animals; Benzofurans; Cleft Palate; Dioxins; Embryo, Mammalian; Female; Gestational Age; Maternal-Fetal Exchange; Mice; Mice, Inbred C57BL; Polychlorinated Dibenzodioxins; Pregnancy; Teratogens; Tissue Distribution

A fire in the State Office Building in Binghamton, New York, involving a polychlorinated biphenyl-containing electrical transformer, resulted in contamination of the structure with soot containing 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran. Benzene extracts of soot collected from various areas of the building were tested for in vitro keratinization-inducing activity by the method of J. C. Knutson and A. Poland (Cell 22, 27-36, 1980). The results, in terms of relative keratinization-inducing activity, are compared to a high-resolution gas chromatographic/mass spectrometric analysis for total polychlorinated dibenzofurans in the same samples. This comparison showed a good correlation and suggests that the in vitro keratinization model has potential for use as a semiquantitative assay for dioxinlike activity.

Topics: Air Pollutants; Benzofurans; Carbon; Cell Line; Humans; Keratins; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins

Topics: Animals; Benzofurans; Birds; Dioxins; Environmental Pollutants; Polychlorinated Biphenyls; Salmon; Soil Pollutants

A series of recombinant inbred strains called BXD [produced from a cross between C57BL/6J (B6) and DBA/2J (D2)] were given single i.p. doses of 0.6 mg/kg 2,3,7, 8-tetrachlorodibenzofuran (TCDBF) on day 12 of gestation. The uteri were examined in late gestation with respect to resorptions and fetal death, and fetal malformations. The strains of the B6-type with respect to Ah-locus (Nos. 5, 6, 8, 11, 12, 14, 16 and 29) that are Ah-responsive, exhibited cleft palates in 80-100% of all fetuses, while hydronephrosis occurred at a rate of 20-70%. These two types of malformation are well recognized from earlier experiments with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and its structural analogues, including TCDBF. In the strains of D2-type with respect to Ah-locus (Nos. 2, 15, 19, 21, 22, 24, and 31), which are Ah-nonresponsive, no cleft palates occurred. One strain (No. 2) had a few (17%) fetuses with hydronephrosis. The frequency of fetal deaths and resorptions were relatively low, but slightly higher among B6-strains than D2-strains. The results indicate an association between the genes producing malformations by TCDBF and the Ah-locus.

Topics: Abnormalities, Drug-Induced; Animals; Benzofurans; Chromosome Mapping; Cleft Palate; Female; Fetal Resorption; Hydronephrosis; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Inbred Strains; Polychlorinated Dibenzodioxins; Pregnancy

2,3,7,8-Tetrachlorodibenzofuran (TCDBF) was administered in single doses (0.1-0.8 mg/kg body weight) intraperitoneally to pregnant C57BL mice on d 10, 11, 12, or 13 of gestation. A dose-dependent increase was observed in the frequency of fetal resorptions and fetal death, especially in the earlier stages (d 10-11). Cleft palate and hydronephrosis as well appeared in a dose-dependent manner, with a peak in sensitivity after administration on d 11-12. TCDBF given at a dose level of 0.1 mg/kg body weight on d 12 of gestation (only dose- and stage-tested) produced a marked thymic hypoplasia as well. A few cases of general hydrops occurred. The pattern of malformations and time of sensitivity corresponded well to that observed earlier after administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; ED50 approximately equal to 25 micrograms/kg) and 3,3',4,4'-tetrachloroazoxybenzene (TCAOB; ED50 approximately equal to 6 mg/kg), two congeners of TCDBF, indicating common mechanisms of action of this family of compounds. Ornithine decarboxylase (ODC) is an important enzyme in cell proliferation and growth with a high activity in embryonic tissues. Liver ODC activity has previously been found to be stimulated by TCDD in weaning mice. However, this enzyme was not found to be stimulated in fetal and placental tissues, but slightly in maternal kidney after treatment with TCDBF in teratogenic doses. It is possible that the ODC activity increases under certain conditions only, on administration of TCDD and its congeners.

Topics: Abnormalities, Drug-Induced; Animals; Benzofurans; Dose-Response Relationship, Drug; Environmental Pollutants; Female; Fetus; Mice; Mice, Inbred C57BL; Ornithine Decarboxylase; Polychlorinated Dibenzodioxins; Pregnancy

Treatment of pregnant C57BL/6N mice with 2,3,7,8-tetrachlorodibenzofuran (TCDF) (0, 250, 500, and 1000 micrograms/kg on gestation day 10 or 0, 10, 30, 50, and 100 micrograms/kg on gestation days 10-13) results in dose-related increases in isolated cleft palates and hydronephrotic kidneys in the offspring. TCDF is teratogenic in 100% of the fetuses at dose levels that are not maternally toxic. The fetal kidney is the most sensitive target organ but the kidney lesions may be reversible.

Topics: Abnormalities, Drug-Induced; Animals; Benzofurans; Cleft Palate; Female; Fetal Death; Gestational Age; Hydronephrosis; Maternal-Fetal Exchange; Mice; Mice, Inbred C57BL; Pregnancy; Teratogens

A flow-limited physiological model was developed to describe the time course of 2,3,7,8-tetrachlorodibenzofuran (TCDF) in the blood and tissues of rats, mice, and monkeys. The liver showed the greatest tendency to concentrate the material with tissue-to-blood distribution coefficients ranging from 30 in the monkey to 130 in the mouse. TCDF was also concentrated in the fat with tissue-to-blood distribution coefficients between 25 and 40 in all species. TCDF was eliminated by metabolism followed by excretion primarily to the feces. Urinary excretion was a minor route of elimination in all species. Metabolism was modeled as a linear process occurring in the liver. Intrinsic metabolic clearances ranged from 0.45 ml/min/kg in the monkey to 2.8 ml/min/kg in one species of mice. Fecal excretion of TCDF-derived radioactivity can be simulated with a series of well-mixed compartments which receive input of metabolites in the bile.

Topics: Animals; Benzofurans; Environmental Pollutants; Haplorhini; Kinetics; Liver; Metabolic Clearance Rate; Mice; Mice, Inbred Strains; Models, Biological; Rats; Species Specificity

Topics: Animals; Benzofurans; Environmental Pollutants; Gastric Mucosa; Macaca mulatta; Male; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Sebaceous Glands; Thymus Gland

Topics: Animals; Benzofurans; Feces; Kinetics; Macaca mulatta; Tissue Distribution

Topics: Adipose Tissue; Administration, Oral; Aging; Animals; Benzofurans; Body Weight; Guinea Pigs; Injections, Intravenous; Liver; Male; Skin; Tissue Distribution

Topics: Animals; Benzofurans; Half-Life; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Species Specificity; Tissue Distribution

1 The minimum toxic dose of tetrachloro-dibenzo-p-dioxin (TCDD) for man has been calculated from monkey and human data to be 0.1 microgram kg-1. 2 The amount of TCDD which man takes in from his environment is about 1/2050 of that present in one square metre of his immediate environment. 3 The average concentration of TCDD present in Vietnam immediately after spraying Agent Orange was 8 microgram m-2. 4 A soldier directly sprayed would attain an internal body concentration of 7 X 10(-5) microgram kg-1 or 1/1750 of the minimum toxic dose; soldiers moving through previously sprayed areas would ingest much less. 5 These quantitative aspects indicate that the dioxin sprayed with Agent Orange in Vietnam cannot have caused systemic illnesses in Vietnam veterans or birth defects in their children.

Topics: 2,4-Dichlorophenoxyacetic Acid; 2,4,5-Trichlorophenoxyacetic Acid; Abnormalities, Drug-Induced; Agent Orange; Animals; Benzofurans; Dioxins; Environmental Pollutants; Female; Food Contamination; Herbicides; Humans; Male; Polychlorinated Dibenzodioxins; Pregnancy; Soil Pollutants; Vietnam

Topics: Adipose Tissue; Animals; Aroclors; Benzofurans; Environmental Pollutants; Haplorhini; Liver; Radioimmunoassay; Rats

Topics: Animals; Benzofurans; Bile; Biotransformation; Kinetics; Male; Rats; Tissue Distribution

The effects of TCDF exposure on the immune system were investigated in Hartley guinea pigs. TCDF was administered by gavage at doses of 0.05, 0.17, 0.5 or 1.0 microgram/kg body weight once weekly for six weeks. Thymus/body weight ratios were suppressed in the higher dosage groups. Parameters of cell-mediated and humoral immune function were investigated. TCDF modestly suppressed cell-mediated immune function and had slight effects on humoral-mediated functions. TCDF immunosuppression appears similar to that induced following exposure to TCDD.

Topics: Animals; Antibody Formation; Benzofurans; Blood Proteins; Cell Division; Female; Guinea Pigs; Hydrocortisone; Immunity; Immunity, Cellular; Leukocyte Count; Lymphocytes; Organ Size; Thymidine; Time Factors