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(346) Assessment of the Reproductive Axis: Comparing Critical Periods of Hormone Sensitivity.
Foran, Christy*,1, Peterson, Bethany2, Tilton, Susan3, Arcand-Hoy, Lisa4, Nimrod-Perkins, Alison5, Benson, William6, 1 West Virginia University, Morgantown, WV, USA2 University of Mississippi, University, MS, USA3 Oregon State University, Corvallis, OR, USA4 BBL Sciences, Syracuse, NY, USA5 Eli Lilly and Company, Greenfield, IN, USA6 U. S. Environmental Protection Agency, Gulf Breeze, FL, USA
ABSTRACT- Japanese medaka (Oryzias latipes) have been developed as a model species to compare the effects of endocrine active chemicals at critical life-stage periods of hormonal sensitivity, specifically as reproductively active adults, during the developmental period of differentiation, and parental or in ovo exposure. Steroid hormones have feedback mechanisms at the level of the pituitary and hypothalamus, but also act on target tissues to stimulate and maintain the reproductive tract and regulate gametogenesis in the gonads. Assessment of reproductive output of exposed adults can be correlated to changes in physiological function along the reproductive axis, including circulating steroid hormone concentrations, ex vivo steroidogenesis from the gonads, pituitary responsiveness to gonadotropin releasing hormone, hepatic estrogen receptor content, and hepatic vitellogenin. Adult exposure provides baseline data for the relationship between exposure and impairment of the reproductive axis. Developmental exposure either as hatchlings or in ovo allows us to determine persistent adult effects of endocrine disruptors. In addition, parental or in ovo exposure allows the separation of potential effects of gametic imprinting and steroid sequestering from impacts of exposure during differentiation. Our results with cadmium, ethinylestradiol and trenbolone indicate that the relationship between biomarkers and exposure will be further complicated by the mechanism of action of the endocrine active chemical and the timing of exposure.
Key words: transgenerational, imprinting, reproduction, brain-pituitary-gonadal axis
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