The sensitivity to endocrine disruptors and the establishment of sensitive bioassay for endocrine disruptors in poultry

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1.Aromatic hydrocarbon receptor (AhR ; dioxin receptor) mRNA expression with aging.We detected the expression of AhR mRNA in various tissues of female chickens with aging (0 to 390 days old) by RT-PCR. As a result, AhR mRNA was detected in gizzard, liver, lung, kidney and heart during all stages. However, the oviduct and bone marrow of female chickens represented no AhR mRNA at 0-day stage and less at 30-90-day stages, respectively. These results suggest that the sensitivities of oviduct and bone marrow to dioxin are altered according to the age of female chickens.2.Expression and localization of AhR in oviduct of laying chickens.AhR expression was detected in magnum, isthmus and shell gland of oviducts by western blotting analysis. Especially in isthmus and shell gland, AhR was strongly localized in the cytoplasm of their epithelial cells. These results suggest that dioxin directly disrupts the metabolism of isthmus and shell gland, resulting in the eggshell weakness.3.In Vivo bioassa … More y of endocrine disruptors using avian medullary bone.The treatment of male Japanese quail with DDE (10mg/day) for 7 days induced medullary bone formation in marrow cavities of femurs. Concomitantly, the treatment increased the serum vitellogenin levels. These results suggest that avian medullary bone formation is superior as in vivo bioassay model of endocrine disruptors.4.Expression and localization of endocrine disrupter receptors in avian medullary bone.Estrogen receptor (α and β) and androgen receptor are well known as receptors for endocrine disruptor. In the present study by in situ hybridization and immunohistochemical analyses, both receptors (especially α subtype in estrogen receptor) were localized in osteoblasts of chicken medullary bone. These results suggest that endocrine disruptors directly act on osteoblastic bone formation.5.RT-PCR analysis of vitellogenin mRNA expression in avian liver.We tried to detect vitellogenin mRNA expression in liver of male quails treated with estrogen receptor agonists. As a result, vitellogenin mRNA expression was induced by estrogen receptor α agonist but not estrogen receptor β agonist. This indicates that vitellogenin synthesis in liver is stimulated through estrogen receptor α. Less