Regulation of Estradiol-17beta Synthesis by Small Follicles of the Domestic Hen Ovary

121 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1992.Small follicles are essential for successful reproduction of the hen because they are the source of follicles recruited into the hierarchy and the major source of estrogen. Estrogen is essential for yolk synthesis, egg shell formation, and other reproductive functions in the domestic hen. Although steroidogenesis in preovulatory follicles has been studied extensively, regulation of steroidogenesis in small follicles has received little attention. Therefore, the aim of my dissertation was to investigate the regulation of E$\sb2$ synthesis by small follicles of the hen ovary. Intact small follicles and follicles shells did not use exogenous cholesterol for E$\sb2$ production in vitro due to the saturating level of endogenous cholesterol. Nevertheless, intact follicles and follicle shells produced steroids in a dose-dependent manner in response to increasing concentrations of P$\sb5,$ DHEA, and P$\sb4.$ DHEA was preferred by small follicles for steroid production, suggesting that the $\Delta\sp5$ pathway may be dominant in small follicles. Steroidogenic pathways use by tissues was investigated by thin layer chromatography. Immature small follicles primarily converted P$\sb5$ to DHEA through the $\Delta\sp5$ pathway. But both $\Delta\sp4$ and $\Delta\sp5$ pathways were functional in granulosa and theca layers of preovulatory follicles. The $\Delta\sp4$ pathway was dominant in the granulosa layer, whereas the $\Delta\sp5$ pathway was dominant in the theca layer. LH-stimulated E$\sb2$ production by small follicles is regulated by a stimulatory PKA system and an inhibitory PKC system. The interaction of PKA and PKC second messenger systems may be needed for the fine-tuned regulation of E$\sb2$ production.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD