Steroid biosynthesis in vitro by the gonads of Sparus auratus L. (Teleostei) at different stages during natural sex reversal

The metabolism in vitro of pregnenolone-4- 14C by the gonads of Sparus auratus L., a protandrous hermaphroditic teleost, was studied during sexual maturity in the male and female phases and during sex reversal. Steroids were identified by their mobilities on thin-layer chromatograms, derivative formation, and recrystallization to constant specific activity, and their yield-time curves were plotted. Progesterone and 17α-hydroxyprogesterone were in every case the most abundant metabolites isolated, and the only ones identified in incubates with ovarian tissue during sex reversal. Some androstenedione was produced by mature testicular tissue, testicular tissue during reversal, and mature ovarian tissue, but only in the first case was there a significant further conversion to testosterone. Although estrogen production was always very small, estradiol-17β and estrone were isolated. Their formation was greater in mature ovarian tissue than in testicular preparations. The gonadal steroids of Sparus auratus L. do not seem to differ from those already described in various gonochoristic species. During sex reversal, gonadal steroid biosynthesis is probably at a minimum, with little interaction between the coexisting testicular and ovarian tissues.