Testosterone inhibits and induces apoptosis in rat seminiferous tubules in a stage-specific manner: in situ quantification in squash preparations after administration of ethane dimethane sulfonate.

The quantitative effects of ethane dimethane sulfonate (EDS), a Leydig cell toxin, on apoptosis in adult rat seminiferous epithelium were studied by the improved transillumination method. Nonradioactive in situ end labeling of fragmented DNA in squash preparations revealed significant increases in apoptotic cells in stages II-XI, whereas controls showed 0.5-2.3 apoptotic cells/mm tubule. Seven days post-EDS treatment, the highest numbers of apoptotic cells were scored in stages VIIab and VIIcd (74.7 +/- 23.8 and 61.3 +/- 16.0 cells/mm, respectively). The effects were suppressed by testosterone (T) supplementation, except in stages II-III and VIIcd. An opposite effect was found in stage XII, where the number of apoptotic cells decreased 1, 3, and 7 days after EDS treatment and returned to control levels in T-supplemented rats. Electrophoretic analysis of internucleosomal DNA fragmentation revealed a biphasic apoptotic process after 1 and 5-7 days due to Leydig and germ cell apoptosis, respectively. The specific germ cell apoptosis was also confirmed by electron microscopic analysis. The results suggest that T withdrawal induces apoptotic cell death in most stages of the cycle and that the effects are largely preventable. In stage XII, however, T seems to promote apoptosis in premeiotic cells.