Meeting Abstract

99.2  Wednesday, Jan. 7  Characterizing the biological activity of estradiol sulfate during embryonic development: Inactive steroid metabolite or precursor for steroid production? PAITZ, RT*; BOWDEN, RM; Illinois St. Univ.; Illinois St. Univ.

Steroids are known to play an important role in directing sexual differentiation of vertebrates. Traditionally, research has focused on the embryonic gonads as the primary source of these steroids, but more recent work has shown that steroids of maternal origin can also influence offspring development. In oviparous vertebrates, these maternal steroids can be present in relatively high concentrations in the yolk at oviposition and create a situation where embryos must begin development in an environment already rich with steroid signals. This may be especially important in some oviparous reptiles where it is has been shown that the sex of the developing embryo can be influenced by steroids. We recently demonstrated that estradiol present in the yolk of red-eared slider (Trachemys scripta) eggs is converted to a water-soluble form during the first 15 days of development and that estrogen sulfotransferase (an enzyme that converts estradiol to estradiol sulfate) activity significantly increases over this same period. At this point it is unknown what the biological activity of these conjugated metabolites may be, so the goal of this study was to test the effects of estradiol sulfate on embryonic development. We predicted that estradiol sulfate application would lead to an increased production of females, similar to what is seen following the application of estradiol. To test this, we applied varying doses of estradiol sulfate to T. scripta eggs at two different points of development. Hatchling sex will be determined to test for any effects estradiol sulfate may have on sex determination. If estradiol sulfate application does not influence sex ratios, it would suggest that embryos may be able to buffer themselves from maternal estradiol.