Accelerated differentiation in seminiferous tubules of fetal mice prenatally exposed to ethinyl estradiol.

Ethinyl estradiol (EE) in olive oil (0.02, 0.2, or 2.0 mg/kg) administered to pregnant mice on days 11 to 17 of pregnancy induced abnormal differentiation of gonocytes and fetal Sertoli cells in male fetuses on day 18 of gestation. Light and electron microscopic examination of the testes showed fewer darkly stained prospermatogonia and more lightly stained prospermatogonia in the experimental than in the control fetuses. Widespread degeneration and lysis of gonocytes were seen only in the experimental mice. No spermatogonia type A could be detected. In spite of comparable mitotic rates in the Sertoli cells of the experimental and control mice and more dark Sertoli cells with well developed smooth endoplasmic reticulum (SER) in the experimental mice, one of the functions of fetal Sertoli cells was suppressed: there were fewer dark slender Sertoli cells with long processes extending to the centers of tubules and more contact areas with gonocytes, phenomena which may play a role in the migration of gonocytes towards the periphery of the tubules. More Sertoli cells were detected in the undescended than the descended testes exposed to the highest dose of EE. These morphological findings indicate that prenatal exposure to EE induces acceleration of prespermatogenesis and disturbances in the initiation of spermatogenesis and in the mechanical function of Sertoli cells.