Changes in food intake and food selection in rats after 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) exposure

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on food selection were studied in TCDD-resistant Han/Wistar and TCDD-sensitive Long-Evans rats and their crosses. The rats were offered a selection diet consisting of chocolate, cheese, and chow, and TCDD was given at the same time or 4 or 16 days later. TCDD persistently reduced the chocolate intake. When the selection diet was started at the time of or less than 11 h after TCDD exposure, TCDD almost completely prevented the intake of chocolate and also cheese in all strains already on the first day, while controls started to consume large amounts of both foods. This may be due to conditioned taste aversion. The effect on food selection with familiar foods seemed to reduce fat intake, while protein and carbohydrate intakes were more variable. There were no major strain differences in the chocolate intake inhibition despite a 1000-fold sensitivity difference in TCDD lethality.     

Learning in monkeys exposed perinatally to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

TCDD is an extremely toxic chemical pollutant which bioaccumulates in maternal adipose tissue, and is transferred to the developing organism during gestation and lactation. Long-term cognitive deficits have been reported following perinatal exposure to polychlorinated biphenyls, which are structurally and toxicologically similar to TCDD. In the current study, monkeys exposed to TCDD perinatally were later tested in two cognitive paradigms, discrimination-reversal learning (RL) and delayed spatial alternation (DSA). RL detected effects; whereas DSA, as analyzed, did not. RL consisted of a series of simple spatial reversals, followed by spatial reversals with color and shape as irrelevant cues, then by color reversals and finally by shape reversals. TCDD-exposed monkeys exhibited retarded learning of the shape reversals. The deficit was most pronounced on the first reversal following overtraining. There were no group differences on the spatial or color reversals. However, the number of trials the TCDD-exposed monkeys individually took to learn the spatial reversals was positively correlated with TCDD concentration in body fat. Conversely, the number of trials they took to learn the color reversals was negatively correlated with TCDD in body fat.     

Acute myelotoxic responses in mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Blood cells are derived from a multitiered system of progenitor stem cells that lose their capacity for proliferation and self-renewal as they continue along pathways of differentiation. Since these hematopoietic events can be readily monitored in vivo and in vitro in the mouse, we have utilized this system to examine altered cellular differentiation associated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity. Progenitor cells were suppressed following acute exposure of mice to TCDD at doses as low as 1.0 micrograms/kg body wt. In vitro studies demonstrated that myelotoxicity occurs by a direct inhibition of proliferating stem cells. Genetic studies indicated that the myelotoxic responses to TCDD, both in vivo and in vitro, segregate with the Ah locus. In addition, the in vitro myelotoxicity of various polyhalogenated aromatic hydrocarbon congeners correlated with their previously reported ability to induce hepatic microsomal enzyme activity and to bind to an intracellular receptor for TCDD. TCDD was also found to bind specifically to bone marrow cells from Ah-responsive, but not nonresponsive mice, indicating that bone marrow cells possess a specific receptor for TCDD. These data indicate that the myelotoxic response to TCDD is regulated by the Ah receptor present in the target tissue and demonstrates the utility of this system for examining the cellular and molecular events associated with the toxicity of polyhalogenated aromatic hydrocarbons, the prototype for which is TCDD.     

Toxicity of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)

In summary, the toxicity of TCDD has been comprehensively examined in multiple acute, subchronic, and chronic studies. Acute toxicity studies have shown marked species differences, with up to a 10,000-fold difference between the single oral LD50 dose for the guinea pig and hamster. TCDD is capable of causing an acnegenic response in man and a similar skin response in certain animals. It is also a potent inducer of microsomal enzymes in some but not all species. A dose-related suppression of cell-mediated immunity has been observed at higher dose levels in laboratory animals but not in humans manifesting TCDD-induced acnegenic response. TCDD causes a dose-related teratogenic response in mice, with the no-adverse-effect level of 0.1 micrograms TCDD/kg/day. In rats, TCDD causes embryo- and fetotoxicity above the no-adverse-effect level of 0.03-0.125 micrograms/kg/day. Dose-related reproductive effects have also been noted in monkeys at doses that elicit maternal toxicity, and additional long-term studies are presently underway. A multigeneration reproduction study as well as a lifetime chronic toxicity study have been completed with TCDD in rats; in both studies, the no-adverse-effect level was found to be 0.001 microgram TCDD/kg/day. Numerous mutagenic studies have been performed using in vitro plant and microbial test systems as well as in vivo tests in mammals and man. A mutagenic response was noted in a few of the vitro test systems, but there are no definitive in vivo correlates of TCDD mutagenicity in higher mammals or man. TCDD has been studied for carcinogenic potential in rats and mice. There is good correlation of the results, with a carcinogenic response noted in both species only after long-term ingestion of higher dose levels that induce toxicity. No carcinogenic response occurred at continuous dose levels of 0.001-0.0014 micrograms/kg/day in rats and 0.001-0.03 micrograms/kg/day in mice. Data presently available are more supportive of a nongenetic (?promotor) rather than a genetic mechanism of carcinogenesis. The most recent research, some of which is still underway, indicates that the biologic uptake and toxicity of TCDD may be significantly decreased if the TCDD is adsorbed onto carbon or soil particles. This information is helpful in hazard assessment of exposure to TCDD.     

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on chorionic gonadotropin secretion by human trophoblasts

This study tests the idea that the environmental toxicant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), affects human trophoblast differentiation and alters the secretion of chorionic gonadotropin (CG). Primary cultures of cytotrophoblast cells were incubated under differentiation-inducing and nondifferentiation-inducing conditions in the presence or absence of different concentrations of TCDD. Levels of immunoreactive CG as well as bioactive CG were measured in culture supernatants. TCDD caused a significant increase in the secretion of immunoreactive CG from differentiated trophoblast cultures but had no effect on the secretion of bioactive hormone. The net effect was a TCDD-dependent reduction in the CG bioactive/immunoreactive (B/I) ratio for differentiated trophoblast cultures. TCDD had no effect on immunoreactive or bioactive CG secretion by undifferentiated trophoblasts. Immunocytochemical studies showed that TCDD had no effect on the morphologic differentiation of trophoblast cells as determined by staining nuclei and desmosomal proteins. On the other hand, immunocytochemical staining for CG was increased in cells exposed to TCDD compared to control cells. These in vitro results support earlier in vivo studies in macaques suggesting that trophoblast is a target for TCCD and that TCDD-induced early pregnancy loss is accompanied by a decrease in the CG B/I ratio.     

CTL hyporesponsiveness induced by 2,3,7, 8-tetrachlorodibenzo-p-dioxin: role of cytokines and apoptosis

Studies have shown that blocking B7-mediated costimulation induces T cell tolerance via anergy or apoptosis. Provision of exogenous IL-2 can reverse or prevent the induction of tolerance. We have previously shown that TCDD-induced suppression of the CTL response to allogeneic P815 tumor cells is accompanied by decreased expression of CD86 (B7-2) as well as suppressed IL-2 and IFNgamma production. In the present studies, the role of IL-2 and IFNgamma and the analysis of inappropriate deletion of CD8(+) cells was examined. Administration of IL-2 on days 7-9 relative to the injection of P815 tumor cells dose-dependently increased the CTL activity and the generation of CD8(+) CTL effector cells in TCDD-treated mice. This increased CTL response was not due to recruitment of naive CTL precursors (CTLp), suggesting that a small pool of activated CTLp in TCDD-treated mice could respond to the IL-2. A much larger pool of activated CTLp in control mice was also expanded by IL-2 treatment. In contrast, treatment with IFNgamma during the same time period did not alter CTL activity in control or TCDD-treated mice. To address the possibility that insufficient IL-2 early in the response was responsible for the reduced pool of activated CTLp in TCDD-treated mice, IL-2 was administered on days 1-3 after P815 injection. However, not only did early treatment with IL-2 fail to restore the response in TCDD-treated mice, it suppressed the CTL response of non-TCDD-treated mice. To test whether exposure to TCDD induced apoptosis of activated CD8(+) T cells, phosphatidylserine (PS) expression was measured on various days after P815 tumor challenge. Surprisingly, the percentage of apoptotic CD8(+) T cells was significantly lower in TCDD-treated mice compared to controls throughout the allograft response. Similarly, exposure to TCDD failed to enhance peripheral deletion of Vbeta3(+)CD8(+) T cells after injection of the superantigen Staphylococcal enterotoxin A (SEA). Taken together, the data indicate that TCDD induces an early defect in CTLp activation that is not due to insufficient IL-2 or deletion of CD8(+) cells and may implicate a novel mechanism by which ligands of the Ah receptor disrupt CTL precursor activation.     

Learning and memory in rats gestationally and lactationally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Recently we reported that in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or coplanar polychlorinated biphenyls (PCBs) resulted in a reduction of errors on a radial arm maze (RAM) working memory task. The effect was more pronounced in males than in females. In this study, we further investigated the effects of in utero and lactational exposure to TCDD on learning and memory by testing male and female TCDD-exposed rats on three different spatial learning and memory tasks: the RAM, the Morris water maze (MWM), and spatial discrimination-reversal learning (RL), as well as on a nonspatial learning task, visual RL. Time-mated Sprague-Dawley rats were gavaged with either TCDD (0.1 microg/kg/day) or corn oil vehicle on gestation days 10-16. Litters were culled to eight on day 2 and weaned on day 21. Beginning on day 80, one male and one female from each litter were tested on the same RAM working memory task used in the previous study. Again, the TCDD-exposed male rats displayed a pronounced decrease in errors relative to control males. Following the RAM testing, the same animals were tested on the MWM, but no differences between the exposed and control rats were observed. Another male and female from each litter were tested on spatial RL on a T-maze. There were no differences between the exposed and control rats on this task. Following spatial RL, the same rats were tested on visual RL on the same maze. The exposed animals did not differ from controls on original learning, but took more trials to reach criterion on the first and second reversals. These results demonstrate a reliable, but task-specific, facilitation of spatial learning and memory in male rats exposed to TCDD during gestation and lactation. In contrast, both male and female TCDD-exposed rats showed a deficit in learning on the visual RL task. This pattern is consistent with that seen in earlier monkey studies. Perinatally TCDD-exposed monkeys were facilitated on certain spatial tasks, but impaired on visual RL tasks.     

Curcumin, myrecen and cineol modulate the percentage of lymphocyte subsets altered by 2,3,7, 8-tetracholorodibenzo-p-dioxins (TCDD) in rats

The aim of this study was to investigate the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a persistent environmental pollutant, on the percentage of T-cell subsets and B-lymphocyte and effectiveness of curcumin, β-myrcene (myrcene) and 1,8-cineole (cineol) on this toxicity in rats. Rats (n = 112) were divided randomly into 8 equal groups. One group was kept as control and given corn oil as carrier. TCDD was orally administered at the dose of 2 μg/kg/week. Curcumin, myrcene and cineol were orally administered by gavages at the doses of 100, 200 and 100 mg/kg/day, respectively, dissolved in corn oil with and without TCDD. The blood samples were taken from half of the rats on day 30 and from the rest on day 60 for the determination of lymphocyte subsets (CD3(+), CD4(+), CD8(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte). The results indicated that although TCDD significantly (p < 0.05) decreased the percentage of CD3(+), CD4(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte, it caused a significant increase in the percentage of CD8(+) cells. In contrast, curcumin, myrcene and cineol significantly decreased CD8(+) cells levels but increased CD3(+), CD4(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte cells populations. The beneficial effects of curcumin, myrcene and cineol and the toxic effects of TCDD were increased at day 60 compared to day 30. In conclusion, curcumin, myrcene and cineol showed immunomodulatory effects and eliminated TCDD-induced immune suppressive effects in rats.     

Fewer T lymphocytes and decreased pulmonary influenza virus burden in mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

The immune system is a sensitive target for the toxicity of the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In mice, immunotoxicity associated with exposure to TCDD includes suppression of humoral and cell-mediated immunity and impaired host resistance to infectious agents. However, the underlying mechanisms for these effects of TCDD are unknown. We previously reported that treatment of C57BI/6 mice with TCDD and influenza A virus increases mortality, impairs cytokine production, and suppresses T cell expansion and the generation of cytotoxic T lymphocytes (CTL) in the draining lymph node. However, the overall virus-specific cytolytic activity in the lung is unaffected. This enigmatic finding left several questions unanswered, including whether decreased CD8+ lymphocytes in the lung are the consequence of either delayed or suppressed recruitment of cells to the lung; whether exposure to TCDD affects the recruitment of CD4+ cells to the lung; and what effect TCDD treatment has on pulmonary virus burden. To compare the kinetics of the response in vehicle- and TCDD-treated mice, we examined the number of bronchoalveolar lavage (BAL) cells and CTL activity in the lung through d 10 postinfection. We found that the peak day for cellular influx and cytolytic activity in the lung is 9 d after infection. Immunophenotypic analysis of BAL cells shows that, when compared with BAL cells from infected controls, exposure to TCDD caused a 50% decrease in the percentage and number of both CD4+ and CD8+ cells. When the pulmonary virus burden was examined over time, we found that on d 1-5 postinfection, lungs from mice exposed to TCDD generally had lower virus titers than lung homogenates from vehicle-treated controls. By d 9 postinfection, no influenza virus was detected in lung homogenates from either vehicle- or TCDD-treated mice. These findings are likely not related to the observed decrease in CD4+ and CD8+ BAL cells; moreover, the diminished CD4+ population in the lung indicates that CD4+ cells are probably not compensating for the decreased CTL generation in TCDD-treated mice. Our observation that mice exposed to TCDD and infected with influenza virus do not have an increased pulmonary virus burden suggests either that TCDD treatment alters the host response to infection, creating a cellular environment that is less supportive for viral growth, or that exposure to TCDD directly affects influenza virus, leading to impaired virus replication within lung epithelial cells.     

ACTH, prolactin, corticosterone and pituitary cyclic AMP responses to repeated stress

The present experiment was conducted to determine whether the plasma hormonal and pituitary cyclic AMP responses observed following a single exposure to an acute stressor would diminish following reexposures to the same stressor. Fifteen-min stress exposures (forced running) were separated by 45-min recovery periods. Separate groups of control and stressed animals were sacrificed before and after each of four 15-min stress periods and after each recovery period. The first exposure to 15 min of forced running raised plasma ACTH, corticosterone and pituitary cyclic AMP levels approximately 6-fold and more than tripled levels of plasma prolactin. Plasma ACTH and pituitary cyclic AMP responses to the second, third and fourth stress exposures were very similar to the responses to the first stress exposure, and levels of these substances returned to prestress levels during each 45-min recovery period. Plasma prolactin responses to the four stress sessions were somewhat variable but no significant trend among the responses was seen. Plasma prolactin levels also returned to prestress levels between stress exposures. Corticosterone levels were similar following each of the four stress sessions but levels remained elevated compared to prestress levels between stress exposures. These data suggest that pituitary responses to acute stress are rapid, that return to prestress levels is also rapid, with the exception of corticosterone, and that repeated responses of the same magnitude may be evoked when stressors are separated by short recovery periods.     

Persistent suppression of contact hypersensitivity, and altered T-cell parameters in F344 rats exposed perinatally to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

The outcome of perinatal low-level TCDD exposure on the T-cell-mediated contact hypersensitivity (CHS) response in adult F344 rats was investigated. Suppression of the 2,4-dinitrofluorobenzene (DNFB)-specific contact hypersensitivity reponse occurred in mature offspring of dams dosed by gavage with 1microg or 3microg TCDD/kg on gestation day (GD) 14. To determine if this effect was correlated with altered distribution or activation of major T-cell subtypes, cells of the auricular lymph node draining the hapten-treated skin were evaluated by flow cytometry for expressed phenotype, including activation markers, 24h after challenge. Six-month-old female offspring with significantly decreased CHS and born to dams given 3microg TCDD/kg, had significantly greater proportion of CD4(+) T cells expressing a naive phenotype marker, CD45RC(hi), in their draining nodes. The greater relative frequency of this CD4(+) subset in peripheral lymphoid tissues associated with a reduced CHS in these rats may be attributed to a reduction in the proportion of CD4(+) T cells maintaining or recruited into an activated state. The CHS proved to be a valuable bioassay for investigating long-term immunotoxic effects of perinatal TCDD exposure in rats.     

Very low-dose (femtomolar) 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) disrupts steroidogenic enzyme mRNAs and steroid secretion by human luteinizing granulosa cells

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic congener of the polyhalogenated aromatic hydrocarbons (PAH), which causes anatomical abnormalities and developmental defects, impairs ovulation and reduces fertility. TCDD's endocrine-disrupting effects are, in part, caused by a direct action at the ovary.Herein we investigated the in-vitro effects of environmentally relevant doses of TCDD on estradiol-17β (E₂) production by human luteinizing granulosa cells (hLGC) obtained from women stimulated for in-vitro fertilization (IVF). TCDD at all concentrations tested (3.1 fM, 3.1 pM and 3.1 nM) significantly decreased E₂ secretion when assayed for by radioimmunoassay (RIA). Herein we confirm that TCDD alters E₂ secretion by hLGC in a time-, not dose-dependent fashion and are the first to show decreases in E₂ secretion with fM concentrations of TCDD. Using real-time quantitative PCR (RT-qPCR), the decreased E₂ secretion correlates with a decrease in the mRNA expression levels two enzymes in the estrogen biosynthesis pathway: CYP11A1 and CYP19A1.     

Characterization of cardiotoxicity induced by 2,3,7, 8-tetrachlorodibenzo-p-dioxin and related chemicals during early chick embryo development

Cardiotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied in White Leghorn-Babcock (WLB) and Plymouth Rock-Barred (PRB) chick embryos. TCDD, injected on day 0 (D0), induced a dose-related increase in heart weight in both strains in the absence of pericardial edema on D10. PRB embryos were four to five times more sensitive to this cardiotoxicity than WLB. To determine if another aryl hydrocarbon receptor agonist produced a similar response, graded doses of TCDD; 3,3',4,4',5-pentachlorobiphenyl (PeCB 126); or 2,2',4,4',5,5'-hexachlorobiphenyl (HxCB 153) were injected into WLB eggs. TCDD and PeCB 126 induced a dose-related increase in heart weight without pericardial edema, while HxCB 153 had no effect. We then hypothesized that TCDD-induced cardiotoxicity progressed to heart failure and edema. In PRB, morphometric analysis revealed that TCDD (0.06-0.45 pmol/g) induced a dose-related increase in left and right ventricle cavity area without wall hypertrophy on D10, consistent with dilated cardiomyopathy. A time course showed that 0.24 pmol/g did not alter heart morphology on D8 but induced cardiac dilation on D10 and D12. The 0.24 pmol/g dose also induced changes associated with progression of cardiomyopathy toward heart failure, including increased cardiac atrial natriuretic factor mRNA expression and decreased cardiac responsiveness to isoproterenol-induced positive chronotropy, on D10 and D12. Finally, 0.24 pmol/g induced a significantly higher incidence of subcutaneous and peritoneal edema, indicative of overt heart failure, on D12 (75%, 15/20) compared to D10 (14%, 3/22). In conclusion, TCDD induced a phenotype of dilated cardiomyopathy and symptoms associated with the development of congestive heart failure.     

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) renders influenza virus-specific CD8+ T cells hyporesponsive to antigen.

While considerable evidence indicates that exposure to the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) impairs T cell function, the precise mechanism underlying this effect is not well understood. Furthermore, relatively little is known about the effects of TCDD on the fate of activated, antigen-specific T cells in vivo. In the present study, we took advantage of major histocompatibility complex (MHC) class I-restricted tetramers and clonotypic anti-T cell receptor (TCR) antibodies to follow the fate of influenza virus-specific CD8+ T cells in mice treated with TCDD. Exposure to TCDD suppressed the clonal expansion of influenza virus-specific CD8+ T cells, resulting in a three- to five-fold reduction in the number of cytotoxic T lymphocytes (CTL) in the lymph node, as compared to vehicle-treated mice. Studies to address possible mechanisms for the diminished CTL response failed to show evidence for increased apoptosis in virus-specific CD8+ T cells from TCDD-exposed mice. However, treatment with TCDD reduced the number of proliferating virus-specific CD8+ T cells by as much as 70% on day 7 post infection. Moreover, ex vivo restimulation of lymph node cells with influenza virus nucleoprotein (NP366-374) peptide and exogenous interleukin-2 (IL-2) only partially restored the proliferation of influenza virus-specific CD8+ T cells from TCDD-exposed mice and failed to stimulate interferon-gamma (IFNgamma) production by these cells. The observation that neither proliferation nor IFNgamma production by CD8+ T cells could be completely restored, even when cells were provided with optimal stimulation, suggests that exposure to TCDD drives antigen-specific CD8+ T cells into a state of unresponsiveness similar to anergy.     

Effects of nicotine on beta-endorphin, alpha MSH, and ACTH secretion by isolated perfused mouse brains and pituitary glands, in vitro

The effects of nicotine on secretion of the pituitary peptides beta-endorphin, alpha MSH, and ACTH were studied using the isolated perfused mouse brain (IPMB) and isolated superfused pituitaries of C3H mice. Nicotine (6.1 microM) stimulated secretion of beta-endorphin immunoreactivity from C3H IPMB approximately twofold. Secretion of alpha MSH immunoreactivity was stimulated approximately two- and sixfold by 6.1 microM and 12.2 microM nicotine, respectively. However, nicotine (6.1 microM) had no direct effect on the secretion of beta-endorphin, alpha MSH, or ACTH immunoreactivities from the isolated superfused pituitaries. The data suggest nicotine acts in the brain to stimulate pituitary secretion of alpha MSH and beta-endorphin. Electrocorticographic (ECoG) activity of the IPMB was monitored. Nicotine induced characteristic ECoG changes including a reduction of input voltage, a biphasic response of rapid desynchronization followed by prolonged synchronization, and seizure at high doses (12.2 microM).     

Absence of lipid peroxidation as determined by ethane exhalation in rats treated with 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)

The exhalation of ethane is widely used as an indicator of in vivo lipid peroxidation. To test the hypothesis that lipid peroxidative events are involved in the toxicity of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), we administered a lethal dose of TCDD (60 g/kg), IP to male Sprague Dawley rats (160–180 g) and measured by gas chromatography the exhalation of ethane into the atmosphere of a closed all-glass exposure chamber. TCDD-treated rats exhaled only slightly more ethane than control rats at a single time point 7 days following TCDD administration. Since the exhalation of ethane is the net result of the endogenous production of the gas and its metabolic degradation, the latter was quantified by measuring the clearance of exogenous ethane (initial concentration = 100 ppm) introduced to the atmosphere of the exposure chamber. The clearance of ethane in TCDD-treated rats was markedly decreased, reaching a minimum 7 days following TCDD treatment. Apparently, the slight increase in exhaled ethane was due to an inhibition of ethane metabolism caused by TCDD. However, rats obviously intoxicated and having lost considerable body weight might be impaired in their ability to transport ethane. To bypass this problem we injected ethane (0.2 ml) directly into the rats IP. Here also the metabolic clearance in TCDD-treated rats was diminished. In a further experiment, rats treated with dithiocarb at a dose where ethane metabolism was totally inhibited exhaled more ethane than did TCDD-treated rats. It is therefore concluded that the slight increase in ethane exhalation following a lethal dose of TCDD is due to a partial inhibition of ethane metabolism and that there is no net increase in ethane production due to lipid peroxidation. Indeed when TCDD-treated rats were administered Fe⁺⁺, a well-known initiator of lipid peroxidation, they were less competent to carry out lipid peroxidation than rats treated with Fe⁺⁺ alone.A preliminary report of this study was presented at the 68th annual meeting of the Federation of American Societies for experimental Biology, St. Louis, MO, USA, April, 1984This work is part of the M.D. thesis of U. Regel     

In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces disruption of glands of the prostate and fibrosis in rhesus monkeys

We investigated the effects that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure has on the prostate in rhesus monkey offspring. Dams received 0, 30 or 300 ng/kg TCDD subcutaneously on Day 20 of gestation, and then 5% of the initial dose was injected every 30 days until Day 90 after delivery. The offspring were maintained until reaching sexual maturity, and examined histopathologically. Dose-dependent decreases in glands of the prostate and widespread fibrosis were observed in offspring. It is noteworthy that 7 years from the final lactational TCDD exposure, inflammatory cell infiltration and disruption of glands of the prostate were still observed. Differential mRNA expression associated with fibrosis, inflammatory response and disruption of cell components were demonstrated by microarray analysis, with up-regulation of TGM4, TGFB1, COL1A1 and MMP2 confirmed. In conclusion, in utero and lactational exposure to TCDD induced dose-related prostatic fibrosis, indicating prostatic dysfunction and inducible semen quality reduction in second-generation rhesus monkeys.     

Changes in fibrinopeptide A peptides in the sera of rats chronically exposed to low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitously distributed endocrine disruptors. To investigate peptide changes in the sera of rats chronically exposed to TCDD and to explore the association of these changes with liver morphology, TCDD was administrated to male rats at doses of 140, 350, and 875 ng/kg/week for 29 weeks. Serum was collected and proteomic analysis was performed using automated Bruker Daltonics ClinProt with matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. One peptide at 1740.89 was found to be significantly decreased and further identified with nano LC-MS/MS system. The MS BLAST homology search engine reported the peptide to be a partial sequence of fibrinopeptide A. Liver fatty degeneration and necrosis were assessed by hematoxylin and eosin staining. Liver fatty degeneration and necrosis were both found to be significantly increased after TCDD exposure. Levels of fibrinopeptide A were significantly correlated with liver fatty degeneration and necrosis.