INTRACRINE ROLE OF PROGESTERONE IN FIBRONECTIN PRODUCTION AND DEPOSITION BY CHICKEN OVARIAN GRANULOSA-CELLS IN-VITRO - EFFECT OF EXTRACELLULAR CALCIUM

The role of extracellular Ca2+ in progesterone-induced fibronectin pro duction and deposition by hen granulosa cells was studied. Granulosa c ells isolated from preovulatory follicles of the chicken ovary were in cubated in Ca2+-deficient or Ca2+-containing medium 193, and the amoun t of total fibronectin produced (fibronectin deposited in the matrix, secreted into the medium, or associated with cells) was measured by EL ISA. The quantity of fibronectin deposited as well as the total amount of fibronectin produced in the presence or absence of exogenous proge sterone was suppressed in Ca2+-deficient medium. It required greater c oncentrations of exogenous progesterone to significantly increase fibr onectin production in Ca2+-deficient medium than in Ca2+-replete mediu m. Cyanoketone, an inhibitor of progesterone synthesis, suppressed tot al fibronectin produced by unstimulated cells both in the absence and presence of Ca2+. However, the inhibitory effect of cyanoketone was si gnificantly 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 gre ater (3-fold) increase in fibronectin production in Ca2+-replete mediu m than in the absence of Ca2+. Thapsigargin, an agent that mobilizes C a2+ from internal stores, suppressed basal and progesterone-induced fi bronectin production in the absence and presence of cyanoketone. Howev er, the inhibitory effect of thapsigargin was significantly reduced in Ca2+-replete medium. It is concluded that endogenous progesterone sti mulates fibronectin production by chicken granulosa cells, probably in an intracrine manner, and that extracellular Ca2+ plays a key role in this process.