Flutamide depresses expression of cortactin in the ectoplasmic specialization between the Sertoli cells and spermatids in the mouse testis

Flutamide (FLUT) has potent anti-androgenic activity and is used in the medical field and in a screening test to detect endocrinologically active compounds. Our previous study demonstrated that FLUT induced histological deformation of spermatids and ultrastructural defects of the apical ectoplasmic specialization (ES) in the mouse testis. The apical ES is an actin-based junctional structure between the Sertoli cells and germ cells. Cortactin, an actin-binding protein, is found in the actin layer of ES. The protein level of cortactin was decreased in FLUT-treated testes as shown by Western blot analysis. The detailed analysis indicated that the protein level was drastically decreased in FLUT-treated seminiferous tubules of stages from VI to IX. histochemistry and immunoelectron microscopy showed that FLUT depressed cortactin expression in the apical ES. In addition, the effect of FLUT on cortactin localization appeared between 12 h and 8 days (about 180 h) after a one-day treatment. These results suggest that FLUT depressed the expression of cortactin in the apical ES with stage specificity. Therefore, the initial target of FLUT may be the cell–cell interactions between the Sertoli and germ cells. To our knowledge, this study is the first to document the decrease of cortactin expression in the abnormal apical ES following treatment with FLUT.