Changes in levels of plasminogen activator activity in normal and germ-cell-depleted testes during development

Abstract

Levels of plasminogen activator activity were determined in testes obtained from normal and irradiated rats of various ages. During normal development, plasminogen activator activity per g testis increased rapidly between 40 and 60 days of age, but a comparable rise did not occur in germ-cell depleted testes of irradiated rats. Levels of enzyme in various populations of testicular cells were highest in Sertoli cells (varying between 1800 and 6300 units/mg protein in cells maintained under different culture conditions), and lowest in peritubular myoid cells (about 1 unit/mg protein), with intermediate levels in germinal cells (ranging between 147 and 560 units/mg protein in residual bodies, spermatocytes and spermatids). No protease inhibitor could be detected in germ-cell extracts. The addition to the medium in which Sertoli cells were in culture of particles which can be phagocytosed (autoclaved E. coil) resulted in an increased formation of plasminogen activator activity by Sertoli cells. A synergistic enhancement of enzyme production resulted following the addition of submaximal quantities of dibutyryl cyclic AMP and autoclaved bacteria to Sertoli cells in culture. On the basis of these data, we suggest that the presence of advanced germinal cells during gonadal development may stimulate the synthesis of plasminogen activator by Sertoli cells, mediated in part by the phagocytosis of residual bodies by Sertoli cells which occurs prior to spermiation.