Androgen action in the epididymis.

Androgens are responsible for maintaining epididymal structure and functions. However, little is known about how androgen action is mediated and the mechanisms underlying the restoration of the integrity of epididymal cells after androgen deprivation. We first provide an overview of what is known about androgen action in this tissue and then present data on the initial and sequential roles of androgens in altering cellular architecture and function in an androgen-deprived condition. Using morphometric analysis and the rat model, we identified changes in epithelial cell height and lumen diameter, as well as in the numbers of proliferating cells in different regions and at various time points after androgen withdrawal and replacement. The sequence of gene activation or suppression that occurred in the androgen-deprived tissue was examined upon the readministration of the 2 active metabolites of testosterone, dihydrotestosterone (DHT) and estradiol. Although few genes were regulated by estradiol, many were affected by DHT. Epidermal growth factor (EGF) and insulinlike growth factor-1 (IGF1) appear to play an important role in the early response pathway activated by DHT because of their function in the regulation of the expression of many other genes. The intracellular signaling pathway involved in mediating the action of androgen in restoring epididymal epithelial cell integrity was investigated using the PC-1 epididymal cell line. IGF1 and EGF receptors were found to be important mediators of androgen receptor-mediated activation of the MAPK/ERK pathways. Together, these studies provide a greater understanding of the mechanisms of androgen action in the epididymis.