HORMONAL-REGULATION OF UROKINASE-TYPE AND TISSUE-TYPE PLASMINOGEN-ACTIVATOR IN RAT SERTOLI CELLS

Tissue type (t) and urokinase type (u) plasminogen activators (PA) hav e been shown to be secreted by Sertoli cells in the seminiferous tubul es in a cyclic fashion and to be dependent upon hormonal stimulation o r the presence of adjacent spermatogenic cells. Furthermore, in cultur ed Sertoli cells, tPA has been shown to respond to FSH induction where as uPA appears to be nonresponsive to gonadotropins. In the present st udy we analyzed the production of PA by Sertoli cells and regulation o f this production by FSH during puberty. Cultured Sertoli cells under basal conditions secreted predominantly uPA. This production was high in 10-day-old animals and gradually decreased in older animals. The tr eatment of cultures with FSH or dibutyl cAMP induced production of tPA by Sertoli cells but at the same time produced a decrease in uPA acti vity. Northern blot analysis revealed that the control of PA synthesis is at the steady-state level of their mRNAs. Moreover, the use of cyc loheximide, a protein synthesis inhibitor, showed that while tPA stimu lation did not require intermediary protein synthesis, the decrease in uPA production was dependent upon protein synthesis. The differences in PA production by Sertoli cells obtained after FSH stimulation could explain the cyclic production of the two enzymes during the spermatog enic cycle and reinforce the hypothesis that different roles are playe d by the two enzymes in the several events occurring in testis develop ment.