Presence and Hormonal Control of Plasminogen Activator in Granulosa Cells of the Domestic Hen1

Plasminogen activator (PA) has been implicated in the control of ovarian cell differentiation and in the process of follicular rupture at the time of ovulation in rats. This study was conducted to evaluate whether PA activity is present in granulosa cells of the largest preovulatory (F1) follicle in the ovary of the domestic hen, and if so, to examine its hormonal regulation. An in vitro assay system, which measures the plasmin-mediated lysis of a chromogenic substrate, S-2251, was validated for use with granulosa cells of the hen to assess levels of both cell-associated and secreted PA. Chicken luteinizing hormone (cLH) suppressed PA activity in a dose-dependent fashion, with the highest dose (100 ng/ml incubation medium) resulting in levels that were 21.8% (cell-associated) and 50.9% (secreted) those of basal values (overall mean of 5 separate assays). Similarly, the ovarian steroid, testosterone, at the lowest dose administered (2 ng/ml medium), was found to inhibit both cell-associated and secreted PA activity (29.0% and 73.0% versus basal, respectively; N=5 assays), whereas progesterone at the highest dose (50 ng/ml media) significantly depressed only cell-associated PA activity (71.9%), but not secreted PA, compared to basal levels (N=5). By contrast, prostaglandin (PG) E1 or PGE2 at 10−6 M, stimulated both cell-associated (a 20.9% and a 32.1% increase, respectively, compared to basal levels) and secreted (a 17.1% and a 28.3% increase, respectively, compared to basal) PA activity (N=5); however, PGE2 at 10−6 M, when combined with cLH at 100 ng/ml, was only partially effective in reversing the inhibitory action of cLH.Finally, epidermal growth factor (EGF) was able to enhance both cell-associated and secreted PA activity (a 256.8% and a 30.1% increase, respectively, compared to controls; N=3). In light of these findings, we conclude that PA activity is present in granulosa cells of the domestic hen, and that this activity is modulated by a variety of hormonal factors. Though the physiological function of this enzyme system is as yet unclear, we propose that it may be involved in the process of ovulation and/or cellular differentiation.