In-situ quantification of stage-specific apoptosis in the rat seminiferous epithelium: effects of short-term experimental cryptorchidism.

Two techniques have been combined for quantification of apoptotic germ cells in defined stages of the cycle of the seminiferous epithelium: the improved transillumination method and nonradioactive in-situ end-labelling of DNA (ISEL). Segments of rat seminiferous tubules were squashed between a microscope slide and coverslip, and the stage identified under a phase-contrast microscope. After fixation, apoptotic cells were detected by ISEL and scored per 1 mm tubule. In the normal testis apoptotic cells were found in all stages, the highest frequency occurring in stages XII-XIV (19 cells/mm). In short-term (24 and 48 h) experimentally cryptorchid testes, a significant increase in number of apoptotic germ cells was evident in all stages, except for VI and VIII. Apoptosis of germ cells was confirmed by electrophoresis of radioactively labelled DNA from stages VII-VIII and XIII-I. It is proposed that apoptosis is a means of eliminating the most sensitive germ cells after short-term experimental cryptorchidism.