Localization of Testicular Plasminogen Activator in Discrete Portions (Stages VII and VIII) of the Seminiferous Tubule

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Abstract
Rat Sertoli cells in culture produce and secrete plasminogen activator, a highly specific protease, and FSH stimulates these processes. Localized proteolysis elicited by plasminogen activator may be implicated in the restructuring of the seminiferous tubule which occurs when spermatocytes in early prophase of meiosis are translocated from the basal to the adluminal compartments. To test this further, tubule segments at different stages of the cycle of the seminiferous epithelium were isolated using transillumination procedures and levels of plasminogen activator in extracts or culture medium in which segments were incubated for 20 h were determined. Levels of plasminogen activator were significantly higher in segments at stages VII and VIII of the cycle and amounts released into the medium by these segments were more than 100-fold greater than those released by segments of seminiferous tubule from any other stage. Segments with seminiferous epithelium at stages VII and VIII are the regions of the tubule in which spermiation occurs, and in which movement of Sertoli cell cytoplasmic processes around leptotene spermatocytes takes place. Plasminogen activator may be intimately related to the localized restructuring which takes place as spermatocytes in meiosis are prepared for translocation into the adluminal compartment and as spermiation occurs at stages VII and VIII in the seminiferous epithelium of the tubule.