Intracrine role of progesterone in fibronectin production and deposition by chicken ovarian granulosa cells in vitro: Effect of extracellular calcium

Abstract

The role of extracellular Ca2+ in progesterone-induced fibronectin production and deposition by hen granulosa cells was studied. Granulosa cells isolated from preovulatory follicles of the chicken ovary were incubated in Ca2+-deficient or Ca2+-containing medium 199, and the amount of total fibronectin produced (Ebronectin deposited in the matrix, secreted into the medium, or associated with cells) was measured by ELISA. The quantity of fibronectin deposited as well as the total amount of fibronectin produced in the presence or absence of exogenous progesterone was suppressed in Ca2+- deficient medium. It required greater concentrations of exogenous progesterone to significantly increase fibronectin production in Ca2+- deficient medium than in Ca2+-replete medium. Cyanoketone, an inhibitor of progesterone synthesis, suppressed total fibronectin produced by unstimulated cells both in the absence and presence of Ca2+. However, the inhibitory effect of cyanoketone was significantly less in Ca2+-replete medium than in Ca2+-deficient medium. Exogenous progesterone reversed completely the inhibitory effects of cyanoketone. In the presence of cyanoketone, progesterone caused a greater (3-fold) increase in fibronectin production in Ca2+replete medium than in the absence of Ca2+. Thapsigargin, an agent that mobilizes Ca2+ from internal stores, suppressed basal and progesterone-induced fibronectin production in the absence and presence of cyanoketone. However, the inhibitory effect of thapsigargin was significantly reduced in Ca2+-replete medium. It is concluded that endogenous progesterone stimulates fibronectin production by chicken granulosa cells, probably in an intracrine manner, and that extracellular Ca2+ plays a key role in this process.