Abstract
The role of progesterone in FSH- and 8-bromo-cAMP (8-Br-cAMP)-induced fibronectin production by chicken ovarian granulosa cells was examined. Granulosa cells isolated from the third largest (F3; developing; 15-20 mm in diameter) preovulatory follicle and a pool of immature small yellow follicles (SYF; 6-8 mm in diameter) were incubated in serum-free medium 199, and the total amount of fibronectin produced (deposited, secreted into the medium, and associated with cells) was measured by enzyme-linked immunosorbent assay. Unstimulated F3 cells deposited greater amounts of fibronectin than unstimulated SYF cells. FSH or 8-Br-cAMP significantly increased fibronectin deposition. Similarly, both agents increased the quantity of fibronectin secreted into the medium and that associated with cells. The magnitude of FSH- and 8-Br-cAMP-enhanced fibronectin deposition or secretion into medium by SYF cells was greater than that by F3 cells. Cyanoketone (an inhibitor of progesterone synthesis) significantly suppressed basal fibronectin production by F3 cells, but not that by SYF cells. Cyanoketone completely blocked FSH- or 8-Br-cAMP-induced fibronectin production by F3 cells, but caused only a modest inhibition (nonsignificant) of agonist-induced fibronectin production by SYF cells. Exogenous progesterone completely reversed the inhibitory effects of cyanoketone on agonist-induced fibronectin production. The nondegradable synthetic progestin R5020 also reversed the inhibitory effects of cyanoketone on agonist-induced fibronectin production. The antiprogestin, ZK 98.299, inhibited basal and FSH-stimulated fibronectin production. The data demonstrate that FSH- and cAMP-stimulated fibronectin production by chicken granulosa cells is dependent (at least in part) on de novo progesterone synthesis. Furthermore, they indicate that fibronectin production and deposition by these cells are stimulated by progesterone, perhaps in an intracrine/autocrine manner, and that the role of progesterone increases with advancing stages of follicular development.
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