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  • 1,2,3,7,8-Pentachlorodibenzo-p-dioxin  (2)
  • Benzo(a)pyrene  (1)
  • Brown adipose tissue  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture (1992)
    Springer
    Archives of toxicology 66 (1992), S. 478-483 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; 1,2,3,7,8-Pentachlorodibenzo-p-dioxin ; 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin ; 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin ; Mixture ; Structure-activity relationship ; Acute toxicity ; Phosphoenolpyruvate carboxykinase ; Pyruvate carboxylase ; γ-Glutamyl transpeptidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Sprague-Dawley rats were treated with an LD20, LD50 and LD80 respectively, of tetra-, penta-, hexa-,hepta-CDD and a mixture of the four CDDs, all carrying chlorine substituents in the biologically crucial 2, 3, 7, and 8 positions. Specific activities of two key enzymes of gluconeogenesis, viz, phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC), as well as the activity of the preneoplastic marker enzyme γ-glutamyl transpeptidase (γ-GT), were determined in livers of CDD-treated and ad libitum-fed control animals. PEPCK activity showed evidence for dose-related inhibition on the second day after dosing; PC activity was slightly reduced, whereas γ-GT activity was dose-dependently inhibited. By 8 days after dosing PEPCK activities were dose-dependently decreased after administration of all four CDDs and their mixture. PC activities were significantly reduced, but no dose-response was evident. The activity of γ-GT was dosedependently inhibited, but only to a value of 25% below control activities. It is concluded that CDDs share a common mechanism of acute toxicity, viz, inhibition of glucocorticoid-dependent enzymes which results in a derailment of intermediary metabolism not compatible with survival of the animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970672
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Tissue-specific alterations of de novo fatty acid synthesis in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-treated rats (1988)
    Springer
    Archives of toxicology 62 (1988), S. 146-151 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; TCDD ; De novo fatty acid synthesis ; Brown adipose tissue ; Thyroid hormones ; Thyroidectomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract De novo fatty acid synthesis was determined by the3H2O method in numerous tissues and organs of TCDD-treated (125 μg/kg), pair-fed and free-fed male Sprague-Dawley rats to investigate if this important pathway of intermediary metabolism is altered by TCDD. Of the 12 tissues and organs examined, liver showed an increased, and interscapular brown adipose tissue (IBAT) a decreased de novo fatty acid synthesis when comparing TCDD-treated to pair-fed or free-fed control rats. De novo fatty acid synthesis was unaffected in other organs and tissues examined, with the exception that the concentration of3H-fatty acids in plasma reflected the increased rate of synthesis seen in the liver of TCDD-treated animals. Increased de novo fatty acid synthesis in liver coincided with increased plasma triiodothyronine (T3) concentrations, whereas decreased de novo fatty acid synthesis in IBAT parallelled decreased plasma thyroxine (T4) levels. Thyroidectomy decreased de novo fatty acid synthesis, as expected, in both liver and IBAT. However, TCDD elicited no response in either of these organs in thyroidectomized rats. This finding suggests that changes observed in non-thyroidectomized rats are probably secondary effects. Indeed, known tissue-specific effects of T3 on liver and T4 on IBAT provide a likely explanation for the altered de novo fatty acid synthesis of these organs. It is suggested that increased de novo fatty acid synthesis in the liver of TCDD-treated rats might be responsible for the additional wasting away observable in these animals as compared to pair-fed controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570132
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture (1992)
    Springer
    Archives of toxicology 66 (1992), S. 484-488 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; 1,2,3,7,8-Pentachlorodibenzo-p-dioxin ; 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin ; 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin ; Mixture ; Structure-activity relationship ; Acute toxicity ; Plasma tryptophan ; Ethoxyresorufin O-deethylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Sprague-Dawley rats were treated with an LD20, an LD50, and an LD80 of 2,3,7,8-tetrachlorodibenzop-dioxin (tetra-CDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (penta-CDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (hexa-CDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (hepta-CDD), respectively, and a mixture of the four homologues where each CDD was represented at one-fourth its previously established LD20, LD50, and LD80, respectively. Plasma tryptophan levels, liver ethoxyresorufin O-deethylase (EROD) activities, and liver weights were determined at 2 and 8 days after treatment. Plasma tryptophan levels were dose-dependently elevated, particularly at 8 days after treatment, by as much as 75% over control levels. EROD activity in CDD-treated animals was induced 27- to 28-fold, as compared with vehicle-treated controls, but did not show any dose-response. Liver weights were also significantly increased by the CDD treatments, but the increase was not dose related. There was no correlation between plasma tryptophan levels, a biomarker of acute toxicity of CDDs, and EROD activity, a biomarker of arylhydrocarbon (Ah) receptor-mediated enzyme induction. It is concluded that the acute toxicity of CDDs, which correlates and shows perfect structure-activity relationship with reduced activities of key enzymes of intermediary metabolism, and the induction of enzymes by much lower doses of CDDs in the liver, have different mechanisms of action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970673
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of selected induction of microsomal and nuclear aryl hydrocarbon monooxygenase and epoxide hydrolase as well as cytoplasmic glutathione S-epoxide transferase on the covalent binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo (1980)
    Springer
    Journal of cancer research and clinical oncology 98 (1980), S. 139-152 
    Details
    ISSN: 1432-1335
    Keywords: Carcinogen ; Benzo(a)pyrene ; DNA binding ; Enzyme induction ; Aryl hydrocarbon monooxygenase ; Epoxide hydrolase ; Glutathione S-transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Groups of four adult male rats [ZUR:SIV-Z] were pretreated with corn oil (control; 2ml/kg/day i.p. for 3 days), trans-stilbene-oxide (SO; 200 mg/kg/day i.p. for 2 days), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10 μg/kg i.p. once, 4 days before killing), phenobarbital (PB; 1 g/liter in the drinking water for 8 days), and dieldrin (20 mg/kg/day i.p. for 3 or 9 days). They received an injection of [G-3H]benzo(a)pyrene (BaP, 31 μg/kg, 7.4·109 dpm/kg;i.v.) 16 h before killing. In the liver of each rat, five enzymatic activities and the covalent binding of BaP to DNA have been determined. The microsomal aryl hydrocarbon monooxygenase activity (AHM) ranged from 75% of control (SO) to 356% (TCDD), the nuclear AHM from 63% (SO) to 333% (TCDD). Microsomal epoxide hydrolase activity (EH) was induced up to 238% (PB), nuclear EH ranged from 86% (TCDD) to 218% (PB). A different extent of induction was observed in the two compartments. Highest induction of glutathione S-epoxide transferase activity (GST) was found with PB (202%). The DNA binding of BaP was modulated within 79% (dieldrin, 9 days) and 238% of control (TCDD). An enzyme digest of control DNA was analysed by Sephadex LH-20 chromatography. Multiple linear regression analysis with all data expressed as % of control yielded the following equation: DNA Binding= 1.49· Microsomal AHM-1.07 · Nuclear AHM+0.33 · Microsomal EH-0.52 · Nuclear EH+0.11 · Cytoplasmic GST+58.2. From this analysis it is concluded that (1) AHM located in the endoplasmic reticulum is most important in the formation of DNA-binding metabolites, (2) EH in the same compartment is not determinative in this respect nor has it a protective effect, (3) both membrane-bound enzyme activities located in the nucleus may inactivate potential ultimate carcinogens, and (4) cytoplasmic GST probably cannot reduce DNA binding due to its subcellular localization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00405958
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    Paper (German National Licenses)
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