In Vitro Steroidogenesis on Oocyte Development in the Starry Flounder, Platichthys stellatus

In this study, oocyte steroidogenesis are investigated in relation to oocyte development in the starry flounder, Platichthys stellatus, a marine multiple spawner. Vitellogenic (0.52 and 0.55 mm oocyte diameter) and mature oocytes (0.63, 0.66 and 0.71 mm oocyte diameter) were incubated in vitro in the presence of [(3)H]17α-hydevrepoxyprogesterone ([(3)H]17α-OHP) as a precursor. Steroid metabolites were extracted from the incubated media and oocytes, the extracts were separated and identified by thin-layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The major metabolites produced from [(3)H]17α-OHP were andevrepogens [andevrepostenedione (A4) and testosterone (T)] and estrogens [17β-estradiol (E2) and estrone (E1)] and progestins [17α,20α-dihydevrepoxy-4-pregnen-3-one (17α20αP) and 17α,20β-dihydevrepoxy-4-pregnen-3-one (17α20βP)] in vitellogenic and mature oocytes. The results from this study suggest the potential roles of E1 in the oocytes with diameter 0.52-0.71 mm, 17α20αP and 17α20βP at the oocytes of 0.63, 0.66 and 0.71 mm.