Effects of follicle-stimulating hormone on the junction-related Sertoli cell cytoskeleton and daily sperm production in testosterone-treated hypophysectomized rats.

Specialized junctional binding of step 8 spermatids to Sertoli cells is an important spermiogenic event. In the hypophysectomized (Hypox) rat, the daily sperm production (DSP) is reduced and Sertoli cells become binding incompetent. Delayed replacement of testosterone (DT-Hypox) does not restore the normal DSP and Sertoli cells remain binding incompetent. In this study, DT-Hypox rats received FSH daily for 2 days to 3 wk concurrent with delayed testosterone replacement and were killed 8 wk after the initiation of hormone treatment. The DT-Hypox rat treated with FSH for 2 days to 2 wk had a significantly reduced DSP. Sertoli cells remained binding incompetent as evidenced by structurally abnormal ectoplasmic specializations and an abnormal pattern of f-actin and vinculin immunostaining. The DT-Hypox rat treated with FSH for 3 wk had a normal DSP. Sertoli cells were binding-competent as evidenced by structurally intact ectoplasmic specializations and the normal pattern of f-actin and vinculin immunostaining. The results indicate that the "priming" effect of FSH necessary to restore normal spermiogenesis is associated with restoration of the junction-related Sertoli cell cytoskeleton (i.e., FSH induction of binding competency) expressed as intact ectoplasmic specializations and peripheral distribution of f-actin and vinculin.