Toxicity of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats after single oral administration

The Protective Effect of α-Tocopherol on the Content of Selected Elements in the Calvaria for Exposed Hens to TCDD in the Early Embryonic Period

This paper focuses on negative effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on element content in male chicken calvaria and α-tocopherol (vitamin E) ability to reduce its toxic potential on bone mineralization in offspring. In the experiment carried out once, a solution containing only DMSO, TCDD, TCDD + α-tocopherol, and exclusively α-tocopherol was administrated. Subsequently, on the 5th day after hatching, the mineral composition of the chicken calvaria was evaluated. The results obtained suggest that the use of α-tocopherol contributes to the maintenance of the concentration of calcium, magnesium, and manganese in the chicken calvaria treated with TCDD in the embryonic period. In turn, vitamin E increases the level of zinc. It has been found that α-tocopherol in chicken embryos has a protective effect against disturbance of level of chosen trace elements in the bones of offspring caused by the TCDD.

The Influence of α-Tocopherol on Serum Biochemical Markers During Experimentally Induced Pleuritis in Rats Exposed to Dioxin

Toxicity of dioxins is wide ranging. Amongst the organs, the liver is the most susceptible to damage by dioxins. Damage caused to liver cells results in promoting inflammatory processes. The aim of this work was to evaluate whether high doses of tocopherol will change the inflammatory response, monitored by biochemical indicators, by improving liver function in rats exposed to tetrachlorodibenzo-p-dioxin (TCDD). The study was conducted on a population of female Buffalo rats. The animals were divided into the following groups: Control Group A—representing physiological norms for the studied diagnostic indicators; Control Group B—subjects were administered a 1% ceragenin solution to induce pleuritis; Study Group 1—where rats were administered α-tocopherol acetate for 3 weeks, after which pleuritis was induced; Study Group 2—rats were administered a single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), while 3 weeks later, pleuritis was induced; and Study Group 3—rats were administered a single dose of TCDD and next, were administered α-tocopherol acetate for 3 weeks, followed by pleuritis induction. The results clearly show that administering tocopherol in the course of inflammation causes changes to the distribution and ratio of in the serum protein fractions, including acute phase proteins. The latter proteins are indicative to the improvement in liver function and linked to protein synthesis and stimulation of the antibody-mediated immunity. Moreover, in the course of inflammation caused by exposure of rats to TCDD, tocopherol significantly affected the acute phase protein concentration.

Assessment of physical traits of rat offspring derived from mothers exposed to dioxin

Negative effects of dioxin action are associated with limited abilities of their bio-degradation along with continuously increasing production and long-term bio-accumulation of those toxins in living organisms. Dioxins penetrate through placenta to fetus indicating indirect toxic effects on offspring of mothers exposed to the action of these toxins. During lactation a significant part of dioxins is excreted from organism with milk, which contributes to further accumulation of those compounds and multiple exceeding of maximal permissible dose of dioxins in newborns feeding with mother's milk. The aim of the study was to determine how a single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) administered to females 3 weeks before getting pregnant affects the parturition duration, labour delay, number and weight of offspring. The studies were performed on rat offspring deriving from primigravida females from the Buffalo strain, which 3 weeks before getting pregnant were administered with a single dose of TCDD. The obtained results revealed that labours in females exposed to dioxin effects were characterized by significant temporal range and their end occurred 3 weeks later compared to females from the control group, which gave birth within a very narrow temporal range ending within 2 days. Offspring obtained from females exposed to the TCDD action was smaller in number and was characterized by smaller rearing and smaller birth weight even after the first month of life; however weight gain in both groups was similar and it was twelve-fold increase.

Effect of tocopherol and acetylsalicylic acid on the biochemical indices of blood in dioxin-exposed rats

New sources of dioxins and increased dioxin concentrations in the environment, coupled with their increased bioavailability along the food chain and accumulation in adipose tissues, contribute to various adverse long-term biological effects. The purpose of the study was to determine whether tocopherol protects the CNS by decreasing the pro-inflammatory influence of free radicals generated by TCDD; whether acetylsalicylic acid inhibits the production of inflammatory mediators; and whether the combined administration of tocopherol and acetylsalicylic acid to TCDD-exposed rats has a potential CNS-protective effect. The study included 117 rats divided into 8 groups: 75 female and 12 male Buffalo rats aged 8-10 weeks, weighing 140-160 g; as well as 30 female rats aged 6 weeks and weighing 120 g, which were the offspring of females from each study group. In the experiment, the following substances were used: 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dosed at 5 μg/kg BW and 12.5 μg/kg BW, diluted in a 1% DMSO solution at the concentration of 1 μg/ml; α-tocopherol acetate, dosed at 30 mg/kg BW, in 0.2 ml of oil solution; and acetylsalicylic acid, 50mg/kg BW, suspended in 0.5 ml of starch solution, administered orally using a feeding tube. Pleurisy was induced by an injection of 0.15 ml of 1% carrageenin solution. The use of tocopherol reduces the adverse effects of the inflammatory reaction induced by TCDD. Administering tocopherol improves protein metabolism by reducing protein catabolism, and raises γ-globulin fraction levels. Combined acetylsalicylic acid and tocopherol suppress catabolic processes accompanying inflammation.

The influence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on hematological parameters during experimentally induced pleuritis in rats

Proper functioning of homeostatic mechanisms is characteristic for every healthy organism and enables adapting to environmental changes. These complicated systematic reactions can neutralize the harmful stress factors leading to various inflammatory reactions. The aim of this study was to determine dynamic changes in the inflammatory reaction after single 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) administration of 5 μg/kg body weight into rats with experimentally induced pleuritis. These changes were observed by monitoring the hematological blood parameters during inflammation. The obtained results proved that dioxins contribute to various changes in the character of the inflammatory response. TCDD administration before pleuritis initiation caused an increase of lymphocytes and significant decrease of the number of neutrophils during inflammation. The current study proved that administration of low TCDD dose (seven times lower than used in other studies) can cause thymus, spleen, or lymphatic gland atrophy. This finding indicates the toxic influence of small TCDD dose especially on the immune system.

Occurrence of disseminated intravascular coagulation in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced pneumonia in the rat

Intensity of inflammatory reaction in tissue or organ structures depends on the efficiency of homeostatic mechanisms of the organism which limit the extent of this reaction. In studies on the dynamics of inflammatory reaction in induced pneumonia after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the occurrence of disseminated intravascular coagulation (DIC) has been observed. In this article we evaluated the DIC syndrome in regard to histopathological assessment and laboratory diagnostics of blood. The evaluation indicates that some hematologic indicators (RBC, HCT, and HGB) decreased in the experimental inflammatory reaction, which might be associated with erythrocyte hemolysis in the inflammatory focus and erythrocyte elimination from circulation as a result of DIC. There also were shifts in the number of various leukocyte forms due likely to the accumulation of particular cells in the inflammatory focus. Histopathological assessment of the inflammatory focus revealed the process of hepatization and the occurrence of DIC.

Polybrominated dibenzo-p-dioxins, dibenzofurans, and biphenyls: inclusion in the toxicity equivalency factor concept for dioxin-like compounds

In 2011, a joint World Health Organization (WHO) and United Nations Environment Programme (UNEP) expert consultation took place, during which the possible inclusion of brominated analogues of the dioxin-like compounds in the WHO Toxicity Equivalency Factor (TEF) scheme was evaluated. The expert panel concluded that polybrominated dibenzo-p-dioxins (PBDDs), dibenzofurans (PBDFs), and some dioxin-like biphenyls (dl-PBBs) may contribute significantly in daily human background exposure to the total dioxin toxic equivalencies (TEQs). These compounds are also commonly found in the aquatic environment. Available data for fish toxicity were evaluated for possible inclusion in the WHO-UNEP TEF scheme (van den Berg et al., 1998). Because of the limited database, it was decided not to derive specific WHO-UNEP TEFs for fish, but for ecotoxicological risk assessment, the use of specific relative effect potencies (REPs) from fish embryo assays is recommended. Based on the limited mammalian REP database for these brominated compounds, it was concluded that sufficient differentiation from the present TEF values of the chlorinated analogues (van den Berg et al., 2006) was not possible. However, the REPs for PBDDs, PBDFs, and non-ortho dl-PBBs in mammals closely follow those of the chlorinated analogues, at least within one order of magnitude. Therefore, the use of similar interim TEF values for brominated and chlorinated congeners for human risk assessment is recommended, pending more detailed information in the future.

Systemic and myelotoxic effects of single administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

OBJECTIVE

Systemic and myelotoxic effects of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) were examined by the single administration of TBDD by gavage to rats.

METHODS

Fifteen Wistar rats of both sexes per group received 0, 10, 30, 100 or 300 μg TBDD/kg body weight. Rats surviving to the scheduled necropsy on Days 2, 7 and 36 after TBDD administration were examined for growth rate, organ weight, hematology, histopathology and adipose tissue levels of TBDD.

RESULTS

Three 300 μg/kg-dosed females died on Days 21, 23 and 27, and exhibited a marked decrease in body weight, severe thymic atrophy, decreased bone marrow hematopoiesis and hemorrhage in the subarachnoid space of brain and spinal cord. TBDD-dosed surviving rats exhibited growth retardation, decreased bone marrow hematopoiesis, decreases in red blood cell counts, hemoglobin concentrations, and hematocrit values, an increase in reticulocytes and decreases in platelet counts, white blood cell counts and eosinophils. These signs suggested TBDD myelotoxicity. Splenic extramedullary hematopoiesis was increased in both sexes given TBDD, whereas atrophy of the splenic white pulp occurred only in TBDD-dosed females. Marked decreases in body weights and the size and weight of the thymus, severe thymic atrophy and death in TBDD-dosed females suggested a wasting syndrome. The adipose tissue level of TBDD culminated on Day 7 and decreased to 20-30% of the Day 7 level on Day 36.

CONCLUSIONS

The TBDD-induced effects were characterized by a wasting syndrome and myelotoxicity that appeared at the dose levels of 30 μg/kg and higher and caused death in 300 μg/kg-dosed females.

In utero and lactational exposure to low doses of chlorinated and brominated dioxins induces deficits in the fear memory of male mice

Environmental-level in utero and lactational exposures to dioxins have been considered to affect brain functions of offspring. Here, we determined whether in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD), at the dose that does not harm the dams, affects the acquisition and retention of fear memory in mouse offspring. Pregnant C57BL/6J mice were administered by gavages TCDD or TBDD at a dose of 0 or 3.0 microg/kg body weight on gestation day 12.5, and their male offspring were examined for their behavior in adulthood. In the fear conditioning, a paired presentation of tone and foot shock was repeated three times, and retention tests for contextual and auditory fear memory were carried out 1 and 24h after the fear conditioning. Groups of mice that were exposed to TCDD and TBDD in utero and via lactation showed deficits in the contextual and auditory retention tests at 1 and 24h retention intervals. The present results suggest that maternal exposure to a low dose of TCDD or TBDD disrupts the functions of memory and emotion in male mouse offspring, and that the developmental toxicities of these chemicals are similar to each other.

Subacute toxicity of polychlorinated naphthalenes and their effect on cytochrome P-450

The aim of the study was to investigate the subacute toxicity of a polychlorinated naphthalene (PCN) mixture and its effect on cytochrome P-450 levels in rats. The animals were administered PCNs intragastrically in repeated daily doses of 1, 10, and 100 mg/kg. The animals were dissected after 7, 14, or 21 doses. Doses of 10 and 100 mg/kg induced a significant decrease in the body weight at all time points of the experiment compared with the control group. The exposure to PCNs increased both the level of total cytochrome P-450 and the activity of CYP 1A at the same time points. In the groups of rats given PCNs in doses of 10 and 100 mg/kg, an evident dose- and time-dependent increase in malondialdehyde (MDA) level was observed throughout the experiment. The correlation between the increased MDA and decreased glutathione (GSH) levels in the liver was also observed.

Occurrence of two different types of glutathione S-transferase placental form-positive hepatocytes after a single administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

Occurrence of glutathione S-transferase placental form (GST-P)-positive hepatocytes was examined, using 15 Wistar rats of both sexes each orally administered 2,3,7,8-tetrabromo-dibenzo-p-dioxin (TBDD) by gavage at a single dose of 0, 10, 30, 100 or 300 microg/kg body weight. Liver tissues were stained with anti-GST-P antibody. Two different types of GST-P-positive hepatocytes were found in the TBDD-dosed rat. One type was of the hepatocytes stained homogeneously with anti-GST-P antibody and clearly distinguishable from the surrounding normal tissue. The foci were composed of 2 to 60 hepatocytes exhibiting morphologically focal and clonal proliferation. The GST-P-positive hepatocellular foci occurred at two higher dose levels and only on Day 36 after the single administration. Another type was of the area occupied by the positively but heterogeneously stained hepatocytes appearing predominantly in the centrilobular region, at lower dose levels and persistently on Day 2 through 36. The stained hepatocytes appeared to be neither focally nor clonally proliferating. Females were more susceptible to formation of the two differently stained hepatocytes than males. It is suggested that the GST-P-positive foci represent an early stage of hepatocarcinogenesis, while the GST-P-positive area is associated with the induction of detoxifying Phase II GSTs.

DOSE- AND TIME-DEPENDENT EFFECTS OF 2,3,7,8-TETRABROMODIBENZO-P-DIOXIN ON RAT LIVER

Dose- and time-dependent effects of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) on the liver were examined by single administration of TBDD by gavage to male and female rats. Fifteen Wistar rats of each sex per group received 0, 10, 30, 100 or 300 microg TBDD/kg body weight. Rats surviving to scheduled necropsy on Day 2, 7 or 36 after the TBDD administration were examined for hepatic histopathology, activities of hepatic microsomal enzymes and serum levels of lipids, total cholesterol and transaminases and hepatic concentrations of TBDD. Tigroid basophilic cytoplasm and hepatocellular hypertrophy were observed at 10 microg/kg on Day 2 or 7 through 36, whereas degenerative and aggressive lesions such as necrosis, fibrosis, multinucleated hepatocytes and disarrangement of hepatocytes occurred later at higher dose levels. Persistently increased activities of hepatic aryl hydrocarbon hydroxylase (AHH), ethoxycoumarin O-deethylase (ECOD) and ethoxyresorufin O-deethylase (EROD), increased serum levels of total cholesterol and phospholipid and increased relative liver weight were observed in all groups dosed 10 mug/kg and above, suggesting that hepatic microsomal monooxygenases and basophilic cytoplasm of hepatocytes were early and sensitive indicators among those TBDD-induced effects. A dose-dependent increase in liver concentrations of TBDD on Day 2 was followed by logarithmic decreases in TBDD concentrations against the days elapsed after the TBDD administration. An elimination half-life (t(1/2)) of TBDD from the liver was estimated to range from 12 to 16 days. It was suggested that females were more susceptible to TBDD than males, and that acute hepatotoxicity of TBDD was as potent as that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Hemopoietic cell kinetics after intraperitoneal single injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widely spread environmental pollutant. Homopoietic system is one of the targets of TCDD in laboratory animals including monkeys. The present study is the hemopoietic cell kinetics in mice, from the severe depression in cellularity of bone marrow and CFU-GM, to their recovery after the intraperitoneal injection of high dosage of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). The bone-marrow cellularity and CFU-GM were severely decreased to 37.8% and 48% of the control, respectively until day 1 after exposure to TCDD. They were, however, soon recovered, even overshot the control value. Subsequently, they tended to show decrease and oscillation again to and under the control value. In conclusion, our cell kinetic study has proven the oscillation in bone-marrow cellularity and CFU-GM during the recovery period, of which the observation seems to be useful to extend our understanding in the hematotoxicity of TCDD.

Toxic effects of the herbicide 2,4-dichlorophenoxyacetic acid on lymphoid organs of the rat

We investigated the toxicity of the widely used herbicide dimethylammonium salt of 2,4-dichlorophenoxyacetic acid (DMA-2,4-D) on the lymphoid system of rats after a single dose oral administration using histological, cytochemical and molecular methods. DMA-2,4-D destroyed in a dose- and time-dependent manner the vascular integrity of the thymus and caused cell depletion in the white pulp of the spleen and in the cortex of the thymus, which was at least partly due to programmed cell death. DMA-2,4-D appeared to have hemolytic activity and caused intravascular hemolysis of erythrocytes. An increased hemosiderin content in macrophages of the spleen indicated phagocytosis of lysed erythrocytes. We conclude that acute DMA-2,4-D herbicide poisoning results in severe damage of the lymphatic organs thymus and spleen.

Tissue distribution after a single subcutaneous administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in comparison with toxicokinetics of 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Wistar rats

Tissue concentrations of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) and induction of ethoxyresorufin O-deethylase (EROD) were determined in female Wistar rats following a single subcutaneous (s.c.) injection of TBDD. Two sets of experiments were performed in order to study (a) the time course after a single s.c. administration of 600 ng TBDD/kg body wt up to 78 days, and (b) the dose-response seven days after a single s.c. injection of different doses of TBDD (3 to 3,000 ng/kg body wt). The results obtained on toxicokinetics and enzyme induction were compared with those following a single s.c. administration of 300 ng/kg body wt 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Three days after the injection, approximately 93% of TBDD and 90% of TCDD had been absorbed. Fourteen days after s.c. injection less than 1% of the administered dose of both substances remained at the injection site. Three days after a single s.c. injection of 600 ng TBDD/kg body wt and 300 ng TCDD/kg body wt, the maximum tissue concentrations in the liver amounted to (M +/- S.D.) 5.7 +/- 0.8 and 4.7 +/- 0.9 ng/g wet weight, respectively. In adipose tissue, the peak concentration was 3.2 +/- 0.2 ng/g wet weight for TBDD on day 14, and 0.8 +/- 0.1 ng/g for TCDD on day 7. Throughout the study, the concentration ratio in the TCDD-treated group was always at least twice as high as that in the TBDD-treated group. The elimination half-life (t1/2) of TBDD and of TCDD in the liver was 13.3 and 13.6 days, respectively. In the adipose tissue the t1/2 of TCDD was 24.5 days but no reliable t1/2 could be calculated for TBDD (t1/2 = 39.4 days with a 95% confidence interval of 25.9 to 82.4 days). Tissue content of TBDD and TCDD in liver and adipose tissue increased dose-dependently, and the linear regression in a double-logarithmic plot showed a straight line. Time course of the induction of hepatic EROD activity after treatment with 600 ng TBDD/kg body wt was almost identical with that observed following a single dose of 300 ng TCDD/kg body wt. The induction of hepatic EROD activity was linearly correlated in a double-logarithmic plot to the hepatic concentrations of the congeners (both TBDD and TCDD). The slopes of the dose-response curves after administration of TBDD and TCDD were almost parallel for tissue concentrations ranging from 0.1 to 30 ng/g wet weight.

Subchronic toxicity of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

2,3,7,8-Tetrabromodibenzo-p-dioxin (2,3,7,8-TBDD) was administered daily to male and female rats for 91 days by gavage. Ten male and 10 female rats per group received 0.01, 0.1, 1, 3, or 10 micrograms 2,3,7,8-TBDD/kg body weight per dose per day, solubilised in arachis oil. At 1 microgram/kg per day and above, body weight gain was dose-dependently reduced by treatment. Animals in the 3 and 10 micrograms/kg dose groups showed symptoms of wasting syndrome. Fifty percent of the animals in the 3 micrograms/kg dose-group died and all animals of the highest dose (10 micrograms/kg) died or had to be killed in extremis. Hematological investigations indicated changes--mainly in the 1 and 3 micrograms/kg dose-groups--in hemoglobin content, packed cell volume and number of thrombocytes. The prothrombin-time was markedly prolonged after 3 micrograms/kg in week 13. Clinical chemistry performed at the end of treatment revealed an increase in plasma alkaline phosphatase (APh), aspartate aminotransferase, ASAT and alanine aminotransferase, ALAT (females only) in the highest surviving dose-group (3 micrograms/kg). Marginal changes of APh and ASAT were seen in rats in the 1 microgram/kg dose-group. In the same animals, total bilirubin was elevated. Triglycerides were reduced mainly at 1 and 3 micrograms/kg. Serum thyroxin was reduced, beginning with a marginal change at 0.1 micrograms/kg, triiodothyronine was elevated, starting with a dose of 1 microgram/kg. Thymus weights were reduced in rats of the 1, 3 and 10 micrograms/kg dose-groups. Histopathological analysis showed atrophy of the lymphatic tissue in thymus and spleen. Investigations of the liver indicated peliosis hepatis after treatment with 3 or 10 micrograms/kg. Activities of microsomal enzymes (ethoxyresorufin O-deethylase, ethoxycoumarin O-deethylase, aryl hydrocarbon hydroxylase, UDP-glucuronyltransferase) investigated in liver, lung and kidney were dose-dependently elevated after 13 weeks of treatment. At a dose of 3.0 micrograms/kg, activities were below those of the dose 1.0 microgram/kg, probably due to liver toxicity. The induction ratio of kidney was generally higher than in liver and lung. No signs of treatment-related toxicity were observed in the 0.01 and 0.1 micrograms/kg groups after the subchronic administration of 2,3,7,8-TBDD by gavage.