Avian Granulosa Cell Prostaglandin Secretion is Regulated by Transforming Growth Factor α and β and Does Not Control Plasminogen Activator Activity during Follicular Development1

The aim of the present study was to determine the role of transforming growth factor alpha (TGFα) and beta (TGFβ) in the regulation of prostaglandin (PG) secretion, and the relationships between PG and plasminogen activator (PA) activity in hen granulosa cells during ovarian follicular development. Cells from the first (F1), third (F3), and fifth and sixth (F5−6) largest preovulatory follicles were cultured for up to 21 h in the presence of TGFα (0.1−10 ng/ml) and/or TGFP (4−20 ng/ml) or TGFα together with a cyclooxygenase inhibitor, indomethacin (0.05−0.5 pM). 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 characterized by zymography. Basal PGF secretion from Fl, F3, and F5−6 cells was 2.2 ± 0.3, 2.2 ± 0.5, and 1.1 ± 0.3 ng/lg DNA, respectively, and 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 103 cpm/μg DNA, respectively. TGFα stimulated PG secretion and PA activity in a dose-dependent manner. The TGFα-induced PA activity was predominantly associated with a molecular mass of 30–35 kDa, corresponding to that of urokinase PA. The stimulation of PG secretion by TGFα was maximal in F3 and F1 granulosa cells whereas PA activity in the presence of TGFα was highest in cells from F5–6 follicles. Dependent on the stage of follicular development, TGFβ suppressed both basal and TGFα-stimulated PG secretion but enhanced the TGFα-induced PA activity. The inhibitory effect of TGFβ on PG secretion induced by TGFα appeared to be more pronounced in the less differentiated cells. Indomethacin inhibited TGFα-induced PG secretion but had no effect on TGFα-induced PA activity. In conclusion, our data show that the ability of avian granulosa cells to produce PGF and PGE is dependent on the stage of preovulatory follicular development. The antagonistic effects of TGFα and TGFβ on PG release suggest a role for the two growth factors in the control of PG secretion by the avian granulosa cells. The regulation of PA activity in granulosa cells by the growth factors is independent of PG secretion and action during preovulatory follicular maturation.