AVIAN GRANULOSA-CELL PROSTAGLANDIN SECRETION IS REGULATED BY TRANSFORMING GROWTH FACTOR-ALPHA AND FACTOR-BETA AND DOES NOT CONTROL PLASMINOGEN-ACTIVATOR ACTIVITY DURING FOLLICULAR DEVELOPMENT

The aim of the present study was to determine the role of transforming growth factor alpha (TGF alpha) and beta (TGF beta) in the regulation of prostaglandin (PG) secretion, and the relationships between PG and plasminogen activator (PA) activity in hen granulosa cells during ova rian follicular development. Cells from the first (F1), third (F3), an d fifth and sixth (F5-6) largest preovulatory follicles were cultured for up to 21 h in the presence of TGF alpha (0.1-10 ng/ml) and/or TGF beta (4-20 ng/ml) or TGF alpha together with a cyclooxygenase inhibito r, indomethacin (0.05-0.5 mu M). The release of PG into the incubation medium was determined by RIA. Cell-associated (PAc) and secreted (PAs ) PA activities were measured by a fibrinolysis assay and characterize d by zymography. Basal PGF secretion from F1, F3, and F5-6 cells was 2 .2 +/- 0.3, 2.2 +/- 0.5, and 1.1 +/- 0.3 ng/mu g DNA, respectively, an d was higher than that of PGE. Basal total PA (PAc+PAs) activity from F1, F3, and F5-6 cells was 41 +/- 13, 261 +/- 68, and 958 +/- 268 x 10 (3) cpm/mu g DNA, respectively. TGF alpha stimulated PG secretion and PA activity in a dose-dependent manner. The TGF alpha-induced PA activ ity was predominantly associated with a molecular mass of 30-35 kDa, c orresponding to that of urokinase PA. The stimulation of PG secretion by TGF alpha was maximal in F3 and F1 granulosa cells whereas PA activ ity in the presence of TGF alpha, was highest in cells from F5-6 folli cles. Dependent on the stage of follicular development, TGF beta suppr essed both basal and TGF alpha-stimulated PG secretion but enhanced th e TGF alpha-induced PA activity. The inhibitory effect of TGF beta on PG secretion induced by TGF alpha appeared to be more pronounced in th e less differentiated cells. Indomethacin inhibited TGF alpha-induced PG secretion but had no effect on TGF alpha-induced PA activity. In co nclusion, our data show that the ability of avian granulosa cells to p roduce PGF and PGE is dependent on the stage of preovulatory follicula r development. The antagonistic effects of TGF alpha and TGF beta on P G release suggest a role for the two growth factors in the control of PG secretion by the avian granulosa cells. The regulation of PA activi ty in granulosa cells by the growth factors is independent of PG secre tion and action during preovulatory follicular maturation.