| Abstrakt: |
Experiments were conducted in vitroto examine the effect of epidermal growth factor (EGF) and transforming growth factor α (TGF-α) on the production of fibronectin (deposited, secreted into medium and cell-associated) by hen granulosa cells isolated from the largest (F1; about 35 mm in diameter, mature) and third largest (F3; 15–20 mm in diameter) preovulatory follicles, as well as from a pool of immature small yellow follicles (6–8 mm in diameter). The cells were incubated in culture wells coated with type IV collagen or in wells without collagen coating, and the amounts of fibronectin produced were measured using a specific ELISA. The total amount of fibronectin produced by unstimulated cells was greatest in wells containing F1cells and increased with time. The amount of fibronectin deposited by unstimulated cells was greatest in wells containing F1cells and was much higher in collagen-coated wells than in uncoated wells. Both EGF and TGF-α increased the quantity of fibronectin deposited by granulosa cells in collagen-coated and uncoated wells. Fibronectin secreted into the medium by unstimulated cells also increased with the stage of follicular maturation and was enhanced by EGF and TGF-α. The quantity of cell-associated fibronectin in granulosa cells in collagen-coated and uncoated wells was also increased by these growth factors. Type IV collagen did not have any appreciable effect on the amount of fibronectin present in the incubation medium or on cell-associated fibronectin. Because of its marked effect on deposited fibronectin, there were greater total quantities of fibronectin in culture wells coated with type IV collagen. These results demonstrate that EGF and TGF-α stimulate the production and deposition of fibronectin by chicken granulosa cells. The results also suggest that in combination with collagen IV, these growth factors can regulate the formation of the extracellular matrix (for example, basal lamina) of the hen ovarian follicle. |
