STEROID-METABOLISM IN GONADS OF TURTLE EMBRYOS AS A FUNCTION OF THE INCUBATION-TEMPERATURE OF EGGS

In embryos of many reptiles, the sexual differentiation of gonads is temperature-dependent. In the turtle Emys orbicularis, all individuals become phenotypic males at 25-degrees-C, whereas 100% phenotypic females are obtained at 30-degrees-C. Steroid metabolism in embryonic gonads was studied at both temperatures, during and after the thermosensitive period for sexual differentiation. Pools of gonads were incubated for various times, with 3-beta-hydroxy-5-pregen-20-one (pregnenolone), progesterone, dehydroepiandrosterone or 4-androstene-3,17-dione as substrates. The analysis of metabolites combined two successive chromatographies (HPLC and TLC) and autoradiography. Conversion of pregnenolone to progesterone and of dehydroepiandrosterone to 4-androstene-3,17-dione was more importan in testes at 25-degrees-C than in ovaries at 30-degrees-C. In ovaries, a large amount of 5-pregnene-3-beta,20-beta-diol was formed from pregnenolone, and 5-androstene-3-beta,17-beta-diol was produced from dehydroepiandrosterone. In both testes and ovaries, 5-alpha-pregnane and 5-alpha-androstane derivatives were the main metabolites obtained from progesterone and 4-androstene-3,17-dione, respectively. Progesterone was also converted to 20-beta-hydroxy-4-pregnen-3-one. Dehydroepiandrosterone and 4-androstene-3,17-dione were also metabolized into 11-beta-hydroxy-4-androstene-3,17-dione (only in testes), testosterone, 11-beta,17-beta-dihydroxy-4-androstene-3-one, 17-beta-hydroxy-4-androstene-3,11-dione (low amounts in testes, traces in ovaries), 17-alpha-hydroxy-4-androstene-3-one, estrone and estradiol-17-beta (traces).