Interactions of transforming growth factor-alpha and -beta and luteinizing hormone in the regulation of plasminogen activator activity in avian granulosa cells during follicular development

Abstract

This study examined the influence of transforming growth factor-alpha (TGF alpha), TGF beta, 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 F1 stage of development. PAc activity was greater than PAm activity regardless of the stage of follicular maturation. TGF alpha (0.1-10 ng/ml) increased PA activity in cultures of granulosa cells from F1, F3, and F5-6 follicles in a concentration-dependent manner. TGF alpha-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 TGF alpha-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. TGF beta (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 TGF alpha-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. TGF alpha and TGF beta, alone or in combination, had no effect on basal P4 secretion at all stages of follicular development. TGF alpha, however, decreased LH-induced P4 secretion in F1 and F3 cultures. These results demonstrate a tightly controlled interaction of TGF alpha, TGF beta, and LH in regulating PA activity and P4 secretion during follicular development in the domestic hen.

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

“…In addition, TGFP may function as a modulator of PA activity in response to TGFa at defined periods during follicular maturation. These observations are consistent with our previous findings [20] that transforming growth factors play an important role in the regulation of granulosa PA activity during follicular development. Moreover, the present data confirm that the TGFca-induced PA corresponded to uPA with a molecular mass of 35 kDa.…”

“…The ability of growth factors to influence PA activity has been documented [20,21,45,46]. The results of the present study on granulosa cell PG secretion also indicate that TGFa stimulates avian granulosa cell PA activity during follicular development.…”

“…In contrast, basal and TGFa-induced PA activity in granulosa cells decreased with follicular development. The observed changes in PA activity with follicular maturation in response to TGFa were predominantly associated with a protease activity within a molecular range of 30-35 kDa (data not shown), one corresponding to that of urokinase PA (uPA) [20,21]. Both basal and TGFa-induced PA activity were markedly higher in cell (PAc) than in medium (PAs) except in the TGFa group of F5-6 (Table 1).…”

“…Previous studies by Tilly et al [39] and Lafrance et al [20] have demonstrated that cells from follicles at different stages of maturation respond to TGFct, while the less differentiated cells from F5-6 also respond to TGF{, suggesting the presence of TGFoa and TGF3 receptors in the hen granulosa cells. The present study extends these observations, demonstrating not only the stimulatory effects of TGFot on PG secretion but also more pronounced stimulation in cells from mature (F1, F3) follicles.…”

“…In the domestic hen, plasminogen activator (PA) activity in cultured granulosa cells from the largest preovulatory follicle is stimulated by PGE 2 [19], suggesting that PG may be involved in the regulation of PA activity in the follicle destined to ovulate. Previous studies from our laboratory have shown that TGFa and TGF0 play important roles in the regulation of granulosa cell proliferation and PA activity during follicular development [20,21]. Whether these changes are mediated by PG secretion and action needs to be clarified.…”