INFLUENCE OF FOLLICULAR MATURATION ON THE DEPOSITION OF FIBRONECTIN BY CHICKEN GRANULOSA-CELLS IN-VITRO - EFFECT OF 8-BROMO-CYCLIC AMP

Fibronectin deposition by avian granulosa cells and the effect of 8-br omo cAMP (8-br-cAMP) on this process was investigated in vitro. Granul osa cells obtained from the first (F1) and third (F3) largest preovula tory follicles and from small yellow follicles (SYF) were incubated in serum free medium 199 for 12 or 24 hr with and without 8-br-cAMP. Fib ronectin deposited in incubation wells, secreted in medium or associat ed with cells was measured by ELISA. Basal fibronectin deposition incr eased with time and was greatest for F1 cells. Within 12 hr, 8-br-cAMP enhanced fibronectin deposition dose-dependently by F3 and SYF cells, but not by F1 cells. The amount of fibronectin deposition caused by 8 -br-cAMP (which was greater after 24 hr incubation) was 0.10- to 0. 16 -fold for F1 cells; 0.20- to 0.81-fold for F3 cells and more than 30-f old for SYF cells. Fibronectin secreted in the medium by unstimulated cells was also greatest in F1 cells. 8-bromo cAMP stimulated fibronect in secretion in medium dose-dependently by F3 and SYF cells, however, it had only a marginal stimulatory effect on this process in F1 cells, Cell-associated fibronectin was not increased significantly by 8-br-c AMP in F1, F3 or SYF cells. Total (deposited plus medium plus cell ass ociated) fibronectin production was elevated in dose- and time-depende nt manner by 8-br-cAMP in F3 and SYF cells, but only at high concentra tions in F1 cells. Like deposited fibronectin, the relative effect of 8-br-cAMP on fibronectin secreted in the medium and on total fibronect in production was greatest in immature SYF cells. These results demons trate that fibronectin synthesized and deposited by unstimulated chick en granulosa cells in vitro increase concomitantly with follicular mat uration and cellular differentiation, and the relative change in fibro nectin production caused by 8-br-cAMP was greatest in immature SYF cel ls.