In vitro effect of vitellogenin on steroid production by ovarian follicles of greenback flounder Rhombosolea tapirina.
Ovarian follicles from vitellogenic greenback flounder (Rhombosolea tapirina) were incubated in L15 medium alone, or containing human chorionic gonadotropin (hCG), dibutyryl cyclic AMP (dbcAMP) or the steroid precursors testosterone (T), 17-hydroxyprogesterone (17P) and androstenedione (A) in the presence of vitellogenin (Vtg) at 0.1-5.0mg mL(-)(1). Medium concentrations of 17beta-estradiol (E(2)) and T were measured by radioimmunoassay. HCG generally stimulated follicular E(2) but not T production, whereas 17P, A and T stimulated production of E(2), T, and E(2) respectively. Treatment of follicles with dbcAMP inhibited follicular E(2) production, but increased follicular T production at high doses. The effect of low concentrations of Vtg on follicular steroid production was variable; however, higher doses of Vtg significantly suppressed basal, hCG-, dbcAMP- and steroid precursor-stimulated follicular E(2) and T production. The results of this study show that high concentrations of Vtg may suppress follicular steroid production by interfering in the steroidogenic pathway. This suggests that Vtg may regulate its own production by limiting the ovarian production of E(2).
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School of Aquaculture, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Locked Bag 1370, Launceston, Tasmania 7250, Australia.
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D019326:17-alpha-Hydroxyprogesterone / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D005432:Flounder / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D006080:Ovarian Follicle / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D013045:Species Specificity; D013256:Steroids / Q000096:biosynthesis*; D013739:Testosterone / Q000096:biosynthesis / Q000494:pharmacology; D014819:Vitellogenins / Q000378:metabolism / Q000494:pharmacology*
D006063:Chorionic Gonadotropin; D013256:Steroids; D014819:Vitellogenins; D013739:Testosterone; D004958:Estradiol; D003994:Bucladesine; D019326:17-alpha-Hydroxyprogesterone