In vitro effect of vitellogenin on steroid production by ovarian follicles of greenback flounder Rhombosolea tapirina.

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Sun, B
Pankhurst, NW
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2006
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Abstract

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 0.1-5.0 mg mL- 1. Medium concentrations of 17߭estradiol (E2) and T were measured by radioimmunoassay. HCG generally stimulated follicular E2 but not T production, whereas 17P, A and T stimulated production of E2, T, and E2 respectively. Treatment of follicles with dbcAMP inhibited follicular E2 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 E2 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 E2.

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Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

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144

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1

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Biochemistry and cell biology

Zoology

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