The comparable levels of the reduction in the number of H+-ATPase-rich cells observed in animals treated with DES and GnRHa are suggestive of a common mechanism in altering the development of this cell phenotype. This most likely centers on interference with androgen production, action, or both, because both GnRHa and DES treatments suppress blood levels of testosterone, and DES (but not GnRHa) treatment causes a major reduction in expression of the androgen receptor protein in the epididymis and vas deferens.
The possibility that the DES effects observed in the present study were at least partially attributed to lower levels of androgens was confirmed by the observation that neonatal coadministration of testosterone with DES was able to restore epididymal expression of H+-ATPase. In addition, H+-ATPase expression in the epididymis was reduced by neonatal flutamide administration. Because flu-tamide induced no change in testis weight or plasma testosterone levels, indicating no suppression of the hypoth-alamo-pituitary axis, the reduction in the number of H+ATPase-rich cells by this agent is presumably due to direct inhibition of epididymal androgen action. Thus, the most unifying explanation for our findings is that altered expression of H+-ATPase in the Day 25 epididymis results directly from insufficient androgen action during neonatal development. However, our results do not exclude the possibility that the effects observed in animals treated neonatally with estrogens, GnRHa, or flutamide are secondary to a general retardation of development of the epididymis, as indicated by the immature morphological appearance of the epididymis under these treatments, which has been described in other studies.