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PT07 Chemical and Biological Analysis of Endocrine Disrupting Compounds
(PT104) Histological correlates of estradiol-induced feminization and intersex formation in Xenopus laevis.
Hu, F1, Carr, J1, 1 Texas Tech University, Lubbock, TX, USA
ABSTRACT- Estrogen or ecoestrogenic chemicals can disrupt normal gonadal development causing hermaphroditism and feminization in amphibians. The cellular basis for estrogen-induced sex reversal is not well understood. In the present study, we investigated the concentration- and stage-dependent effects of estradiol on gonadal histology in the African clawed frog, Xenopus laevis. Embryos were exposed to 1 g/L, 10 g/L, 100 g/L estradiol or vehicle control beginning at Nieuwkoop-Faber-stages 1-10. Sample collections were performed at NF-stage 49, 51, 52, 55, and stage 66. After metamorphosis, the remaining animals were allowed to develop for an additional two-month in untreated FETAX medium. Gonadal differentiation did not occur before NF- stage 52 in all groups. Primordial germ cells (PGCs) were observed in cortical and medulla regions of the developing gonads at NF stage 55 in the 1 g/L and 10 g/L treatment, but were present only in the cortical region in animals exposed to 100 g/L estradiol. The percentage of female offspring was positively correlated with estradiol concentration at the completion of metamorphosis and in the 2-month grow-out animals; 100 % females were observed in the 100 g/L estradiol treatment. About 11% of the animals exposed to 1 g/L estradiol exhibited intersex gonads. Oocyte size was significantly smaller in the intersex animals. Compared with controls, estradiol-treated animals exhibited a greater number of spermatids and spermatozoa, indicating that estradiol might facilitate spermatogenesis. We conclude that the degree of estradiol-induced intersex formation is proportionately related to the degree of PGC migration from the cortex to the medulla of the developing gonad in X. laevis. Estradiol exposure prevents PGC migration in genetic males and this effect is concentration-dependent. Furthermore, we conclude that estradiol-induced feminization is not reversible in X. laevis. Supported in part by a seed grant from TTU.
Key words: Amphibians, Endocrine disruptors, sex differentiation
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