INTERACTIONS OF TRANSFORMING GROWTH-FACTOR-ALPHA AND FACTOR-BETA AND LUTEINIZING-HORMONE IN THE REGULATION OF PLASMINOGEN-ACTIVATOR ACTIVITY IN AVIAN GRANULOSA-CELLS DURING FOLLICULAR DEVELOPMENT

This study examined the influence of transforming growth factor-alpha (TGFalpha), TGFbeta, and LH on progesterone (P4) secretion and plasminogen activator (PA) activity in cultured avian granulosa cells from the first (F1), third (F3), and fifth and sixth (F5-6) preovulatory follicles during a 21 -h incubation period. PA activity in the cell (PAc) and the medium (PAm) fractions was measured by fibrinolysis and fibrin overlay methods. P4 was determined by RIA. Basal PAc and PAm activities were highest in cell cultures from the less mature (F5-6) follicles and decreased as follicles matured to the Fl stage of development. PAc activity was greater than PAm activity regardless of the stage of follicular maturation. TGFalpha (0.1-10 ng/ml) increased PA activity in cultures of granulosa cells from Fl, F3, and F5-6 follicles in a concentration-dependent manner. TGFalpha-induced PAc and PAm activities were observed by 6 and 15 h of incubation, respectively, and increased rapidly between 15-21 h. LH (100 ng/ml) attenuated TGFalpha-induced PA activity by 15 h in cultures of granulosa cells from F1 and F3, but not F5-6, follicles. Basal PA activities were unaffected by the gonadotropin. TGFbeta (2-100 ng/ml) stimulated PAc activity in a dose-dependent manner only in cultures of granulosa cells from F5-6 follicles and significantly enhanced TGFalpha-induced PAc and PAm activities in cell cultures from F3 and F5-6, but not F1, follicles. Basal and growth factor-induced PAc and PAm activities corresponded to a mol wt of about 35 kDa, a value consistent with that of the low mol wt uPA species. TGFalpha and TGFbeta, alone or in combination, had no effect on basal P4 secretion at all stages of follicular development. TGFalpha, however, decreased LH-induced P4 secretion in F1 and F3 cultures. These results demonstrate a tightly controlled interaction of TGFalpha, TGFbeta, and LH in regulating PA activity and P4 secretion during follicular development in the domestic hen.