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In this study, we investigated the effect of organosulfur compounds including, diallyl sulfide (DAS), garlic extract, and dially disulfide (DADS) on inducible expression of UDP-glucuronosyltransferase (UGT1) and thyroid hormone level in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-treated rats. We measured UGT1 gene expression in rat liver and lung tissues after treatments. We found that a correlation was found to exist between UGT1 gene expression and active T-4 concentrations. The total concentration of plasma T-4 decreased in TCDD-alone treated male and female rats compared to control animals (TCDD-alone < control). Plasma T-4 concentration in TCDD + DAS, TCDD + garlic extract and TCDD + DADS treated groups were moderately higher than in TCDD alone animals, but lower than control animals. TCDD + DAS, TCDD + garlic extract and TCDD + DADS moderately increased T-4 glucuronidation and moderately reduced total T-4. The nonthyroidal nature of thyroid hormone reduction observed in this study extends the evidence for microsomal enzyme inducers as indirect thyroid tumor promoters in rats. Furthermore, the results of present study suggest protective effects of DAS, garlic extract, or DADS on TCDD-induced changes.
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