UP-REGULATION OF UROKINASE PLASMINOGEN-ACTIVATOR MESSENGER-RIBONUCLEIC-ACID AND PROTEIN IN HEN GRANULOSA-CELLS BY TRANSFORMING GROWTH-FACTOR-ALPHA IN-VITRO DURING FOLLICULAR DEVELOPMENT

The aim of the present study was to examine the regulatory role of tra nsforming growth factor alpha (TGF alpha) on urokinase plasminogen act ivator (uPA) gene expression and protein levels in hen granulosa cells from different stages of ovarian follicular development in vitro. Cra nulosa cells from the first (F1), the second and third (F2-3), and the fourth, fifth, and sixth (F4-6) largest preovulatory follicles were c ultured for 21 h in the absence and presence of TGF alpha (10 ng/ml). The uPA mRNA abundance and protein content were determined by Northern and Western blot analysis, respectively. Cell-associated and secreted PA activity was measured by a fibrinolysis assay and characterized by zymography. Hen granulosa cells produce a uPA with a molecular mass o f about 35 kDa and a transcript size of approximately 2.5 kb. Basal uP A mRNA abundance, protein content, and activity were highest in granul osa cells from F4-6 follicles and decreased with follicular maturation . Granulosa cell uPA mRNA levels, protein content, and activity were i ncreased in the presence of TGF alpha, reaching maximal levels in gran ulosa cells from less mature follicles, although the percentage of sti mulation was higher in cells from late stages of follicular developmen t. These findings clearly demonstrate specific expression of uPA in pr oliferatively active granulosa cells and responsiveness of uPA to TGF alpha at both transcriptional and translational levels. They support t he concept that PA of the urokinase type plays an important role in ex tracellular matrix remodeling during TGF alpha-induced granulosa cell proliferation and ovarian follicular growth.