IN-VITRO, FOLLICLE-STIMULATING-HORMONE PREVENTS APOPTOSIS AND STIMULATES DEOXYRIBONUCLEIC-ACID SYNTHESIS IN THE RAT SEMINIFEROUS EPITHELIUMIN A STAGE-SPECIFIC FASHION

The effects of FSH on stage-specific apoptosis and DNA synthesis in th e adult rat seminiferous epithelium were studied in vitro. Seminiferou s tubular segments from stages I, V, VIIa, and VIII-IX were cultured f or 24, 48, and 72 h in different concentrations of FSH. Apoptotic cell s were detected by in situ end labeling of DNA strands and quantified from squash preparations. After 48 h of culture, a FSH concentration o f 2 ng/ml prevented apoptosis of early (steps 1-3) spermatids. In stag e VIII-IX tubules cultured for 72 h, FSH decreased the apoptosis of pa chytene spermatocytes. An apoptotic type of cell death of germ cells w as confirmed by DNA laddering, electron microscopy, supravital acridin e orange staining, and phase contrast microscopy of unstained living c ells. The effects of FSH on stage-specific DNA synthesis were studied using the same culture system. FSH increased [H-3]thymidine incorporat ion specifically at stages I and VIII-IX, and autoradiography confirme d stimulation of mitotic and meiotic DNA synthesis in type B spermatog onia and preleptotene spermatocytes, respectively. Increased thymidine incorporation also suggested that FSH stimulated DNA synthesis of typ e A and intermediate spermatogonia. Most effects exerted by FSH were s een in stages containing high levels of FSH receptors and FSH-stimulat ed cAMP production. In conclusion, the results suggest that FSH, proba bly acting via Sertoli cells, has a regulatory function in spermatogen ic apoptosis and DNA synthesis in stages previously demonstrated to be preferentially dependent on FSH stimulation.