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1 May 2011 Effects of Co-Administration of Estrogen and Androgen on Induction of Sex Reversal in the Medaka Oryzias latipes
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Abstract

To investigate how estrogen and androgen affect each other in inducing sex reversal in the medaka, O. Iatipes, 17β-estradiol (E2) and 17α-methyldihydrotestosterone (MDHT) were co-administered by a convenient method for hormonal treatment, in which freshly fertilized eggs were immersed for 24 h in saline containing either or both of the two sex steroids in different concentrations and/or ratios. The minimal concentrations of E2 and MDHT sufficient to induce the maximal rate of sex reversal from male to female and from female to male were 500 ng/ml and 2.5 ng/ml, respectively, both of which were referred to as the most efficacious dose (MED), and each equivalent for the inducing potency in sex reversal. E2 and MDHT, when simultaneously administered at MED, greatly suppressed each other to induce each corresponding sex reversal. Thus, the present experimental results indicate that E2 and DMHT are antagonists that induce corresponding sex reversal, and suggest that genotypic sex in the medaka might be modified through an unknown factor of common affinity to both sex steroids, by which the pathway of differentiation of either sex could be switched at the early stages of development far before gonadal sex differentiation.

© 2011 Zoological Society of Japan
Hirokuni Kobayashi, Takashi Iwamatsu, Yasushi Shibata, Michio Ishihara, and Yasuhisa Kobayashi "Effects of Co-Administration of Estrogen and Androgen on Induction of Sex Reversal in the Medaka Oryzias latipes," Zoological Science 28(5), 355-359, (1 May 2011). https://doi.org/10.2108/zsj.28.355
Received: 27 April 2010; Accepted: 1 October 2010; Published: 1 May 2011
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