Hormonal and immunological characterization of the cell-associated plasminogen activators produced by cultured rat granulosa cells.

The hormonal induction and immunological reactivities of the cell-associated plasminogen activators (PAs) produced by granulosa cells obtained from the ovaries of diethylstilbestrol-implanted immature rats were studied. FSH and other cAMP-inducing ligands, including cholera toxin, forskolin, and 8-bromo-cAMP, elevated the PA activity of granulosa cells in a concentration-dependent manner during a 4-h culture, with an approximate 10-fold maximal increase in PA activity compared to control cells. Negligible levels of PA activity were observed in the extracellular medium in the absence or presence of hormones. The PA induced by FSH or cAMP in intact cells was progressively neutralized during the 4-h culture by increasing amounts of antibodies to the tissue-type PA (tPA), but not by an IgG fraction against the urokinase-type PA (UK-PA). However, solubilization of granulosa cells with Triton X-100 revealed the presence of intracellular UK-PA activity in both FSH-treated and control cells that consisted of about 20% of the total cellular PA activity. Electrophoretic analysis of extracts from solubilized granulosa cells indicated the presence of three peaks of PA activity. A PA with a Mr of 70,000 was induced by FSH, was completely inactivated by tPA antibodies, and required fibrin for full activity. A 40,000 Mr fibrin-independent PA was also stimulated by FSH and was partially inhibited by UK-PA antibodies, but not by anti-tPA immunoglobulin G. A third peak of PA activity comigrated with a human UK-PA standard at a Mr of 33,000, was fully neutralized by UK-PA antibodies, and was largely present only in control cells. These results suggest that during the first hours of granulosa cell development, FSH via cAMP induces the production of a cell-surface tPA, while both FSH-treated and control cells synthesize intracellular UK-PAs. Hormonal regulation of the production and activities of these cellular enzymes may allow the expression of specific differentiated functions of developing granulosa cells.