Failure of Exogenous Androgen to Prevent Regression of the Initial Segments of the Rat Epididymis after Efferent Duct Ligation or Orchidectomy1

This investigation was undertaken to explore further the dependence of the initial segments of the epididymis upon substances in the testicular fluid. The experimental groups consisted of rats castrated, rats with ligated ductuli efferentes and sham operated controls. The epdidymides were examined by light and electron microscopy 3 and 6 weeks postoperatively. The initial segments of the duct in both ligated and castrated animals exhibited 1) striking decrease in duct diameter and epithelial height, 2) a marked decrease in endoplasmic reticulum in the apical cytoplasm, 3) evidence of diminished activity of the Golgi complex, but 4) persistence of fluid uptake by pinocytosis. Daily administration of 500 µg testosterone proprionate beginning on the first postoperative day maintained the accessory gland weights at normal or supranormal values, but was ineffective in preventing the cytological regression of the initial segments of the caput epididymidis. In an effort to achieve levels of androgen in the blood comparable to those normally found in the rete testis fluid, castrated and ligated rats were implanted s.c. with 30 cm of Silastic tubing containing testosterone, each estimated to release 4 mg/day (Berndtson et al., 1974). Plasma testosterone levels when the rats were killed were 8–10 times normal. Despite these high levels of circulating androgen, cytological dedifferentiation of the initial segments was not prevented. More distal segments of the duct were essentially normal in dimensions and appearance. It is concluded that the initial segments of the rat epididymis require high intraluminal concentrations of androgen bound to androgen binding protein. The possibility that they are dependent upon some other, as yet unidentified, constituent of testicular fluid is not ruled out.