Date of Defense


Date of Graduation



Biological Sciences

First Advisor

Christopher Pearl

Second Advisor

John Spitsbergen


Previous studies from our lab have demonstrated that a normal estrogen environment in the testis contributes to maintaining spermatogenesis in adult rats and that estrogen treatment can attenuate the age-associated decline in sperm production. The purpose of this study was to determine if the estrogen environment of the epididymis is altered with age and what effects estrogen treatment may have on the epididymis during aging. The study compared untreated rats at 15 months of age to 18 month old rats that were treated with either vehicle, or estradiol- valerate, once every third day from 15 to 18 months. Mean concentrations of testosterone were highest in the corpus compared to the initial segment/caput and proximal cauda. A similar trend was observed for mean estradiol concentrations with the highest concentration in the corpus. Even though there were significant regional differences in hormone concentrations, the concentrations were similar amongst the three groups. In all three groups, the tubular and luminal diameter of the cauda was significantly larger than the initial segment. In the 15 month old and 18 month old treated animals, the epithelial cell height of the cauda was significantly smaller than that of the initial segment. These regional differences were not seen in the 18 month old animals. Immunocytochemistry demonstrated that ERα was expressed in nuclei of principal cells throughout the epididymis even though the intensity of immunostaining did not appear to differ between treatment groups. However, transit time through the distal cauda was significantly different between treatment groups. Mean transit time was 3.8 days at 15 months of age and increased to 5.5 days at 18 months of age; transit time was 3.3 days in estradiol-valerate treated rats. This suggests that treatment with estradiol-valerate was able to speed up epididymal transit time and prevent the prolonged transit time associated with aging. Collectively these results suggest that the estrogen environment of the epididymis may not change during aging in a manner similar to what was observed in the testis, but epididymal functions, and thus sperm maturation, are likely altered during aging and by estrogen treatment.

Access Setting

Honors Thesis-Open Access