INFLUENCE OF GROWTH-FACTORS ON THE PLASMINOGEN-ACTIVATOR ACTIVITY OF AVIAN GRANULOSA-CELLS FROM FOLLICLES AT DIFFERENT MATURATIONAL STAGES OF PREOVULATORY DEVELOPMENT

Granulosa cells from the first (F1), third (F3) and fifth and sixth (F 5-6) preovulatory follicles and the small yellow follicles (SYFs; diam eter 6-8 mm) were cultured for 21 h in the absence and presence of mur ine and human epidermal growth factors, growth fibroblast growth facto r, transforming, factors alpha and beta-I (TGF alpha, TGF beta), plate let-derisred growth factor and insulin-like growth factor-I at concent rations of 0.1-100 ng/ml. Plasminogen activator (PA) activities in the cell (PAc) and in the medium (PAm) were measured by fibrinolysis and fibrin overlay methods. Basal PAc and PAm activities were highest in c ell cultures from the less mature follicles (F5-6 and SYF) and decreas ed as the follicles matured (F3>F1). PAc activity was greater than PAm activity, irrespective of the stage of follicular development. All gr owth factors examined at the 100 ng/ml level were effective in increas ing PAc and PAm activities in cultures of granulosa cells from F1 foll icles. However, only TGF alpha was able to increase PA activities at l ower concentrations. The stimulation of the PA activities of granulosa cells from F3 follicles was inconsistent. None of the growth factors significantly increased PA activities in granulosa cells from F5-6 fol licles and SYFs, as determined by fibrinolysis. The major PAc and PAm species (characterized by fibrin overlay) had a molecular mass of abou t 35 kDa, which is characteristic of the urokinase type. Both assay me thods detected a stimulatory effect of the growth factors on PA activi ties in the granulosa cells from F1 follicles. However, an increase in PA activities in cells from F3 and F5-6 follicles and SYFs was indica ted only after fibrin overlay analysis. Tritiated thymidine was incorp orated into the DNA of granulosa cells at all stages of follicular dev elopment and was enhanced by all growth factors, although TGF alpha an d TGF beta were the most effective and had a ranked order of activity: F3, F5-6>F1, SYF. The present findings show that, of the growth facto rs examined, TGF alpha may be an effective regulator of PA activity in avian granulosa cells during follicular development, in addition to i ts observed mitogenic action.