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Testicular Damage Caused by Inhalation of Ethylene Oxide in Rats: Light and Electron Microscopic Studies

Although testicular damage caused by ethylene oxide vapor (EtO) has been previously reported, the morphological changes occurring in seminiferous tubules remain unclear. We examined the time course of the testicular lesion induced by EtO in order to clarify its morphogenesis. Wistar rats were exposed to 500 ppm EtO for 6 hr per day, 3 times per week for 2, 4, 6, or 13 weeks through inhalation. In the 2-week exposure group, Sertoli cells often showed condensation and retraction of the cytoplasm, and dilatation of the endoplasmic reticulum (ER). In apical Sertoli cells, processes which encapsulated the heads of elongate spermatids, ectoplasmic specializations, and tubulobulbar complexes were often deformed and many elongate spermatids were degenerated. In the 4- and 6-week exposure groups, many degenerated Sertoli cells were present, and deformed germ cells, sometimes with multinucleation, appeared to make direct contact with each other without interlocation of Sertoli cell lateral processes. A few scattered immature Sertoli cells were evident in the 6-week exposure group. In the 13-week exposure group, seminiferous tubules containing almost all types of germ cells reappeared, mixed with atrophic tubules containing Sertoli cells only. In the former tubules, Sertoli cells often possessed regularly regenerated lateral processes, which were interposed between germ cells. These results indicate that the germ cell damage may be associated with damage to Sertoli cells. In spite of the intermittent exposure, focal regeneration of Sertoli cells appeared after 6 weeks of exposure to EtO and preceded patchy recovery of germ cells. Therefore, the data suggest that Sertoli cell regeneration may permit regeneration of germ cells.