No abstract

1. The purpose of this study was to investigate the effects of epidermal growth factor (EGF) on progesterone (P(4)) secretion from ovarian granulosa cells in Tsaiya ducks (Anas platyrhynchos var. domestica). 2. We obtained the largest (F1) follicle from Tsaiya duck, the granulosa layer was separated and the cells were isolated according to their proximity to the germinal disc. 3. The granulosa cells were cultured in vitro, the culture media and the cells were used to determine P(4) and steroidogenic enzyme concentrations, respectively. 4. P(4) concentrations were decreased in cultured granulosa cells taken proximal to the germinal disc (GD) compared to those distal to the germinal disc (NGD). 5. EGF inhibited both basal and ovine luteinising hormone (oLH)-induced P(4) concentrations. It also inhibited the P(4) secretion via protein kinase A (PKA) pathway when cultured with GD and NGD granulose cells (mixed together) in vitro. 6. Western blot results showed decreased concentrations of cytochrome P450 side-chain cleavage (P450scc) enzyme, 3β-hydroxysteroid dehydrogenase (3β-HSD) enzyme and steroid acute regulatory (StAR) protein expression, when the cells were co-treated with EGF and oLH. 7. The inhibitory effect of oLH-induced P(4) production was attenuated by EGF by the addition of MAP-erk kinase (MEK) inhibitor (PD98059) suggests EGF may inhibit P(4) production by affecting via the mitogen-activated protein kinase (MAPK) pathway.

The corpus luteum (CL) is a transient endocrine gland that produces progesterone, a product required for the establishment and maintenance of pregnancy. In the absence of pregnancy, the production of progesterone in the CL decreases and the structure itself regresses in size. The life span and function of the CL are regulated by complex interactions between stimulatory (luteotrophic) and inhibitory (luteolytic) mediators. When an ovum is released from a mature follicle, angiogenesis and rapid growth of follicular cells form the CL. The purpose of the present study was to determine whether steroidogenesis, proliferation, and hypoxiarelated proteins are expressed in caprine CL. The expression of proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor 1α (HIF-1α) were determined in caprine CL during the estrous cycle. Cytochrome P450 side chain cleavage protein did not vary significantly during the estrous cycle; however, there was an increased expression of 3βhydroxysteroid dehydrogenase in the early and middle stages, which rapidly decreased in the late stage. The same observations were made with respect to steroidogenic acute regulatory protein. Variations in progesterone content and expression of PCNA, HIF-1α, and VEGF were consistent with this result. Thus, the steroidogenic proteins, PCNA, HIF-1α, and VEGF in caprine CL are dependent on the stage of the estrous cycle.