Date Approved


Graduate Degree Type


Degree Name

Biomedical Sciences (M.H.S.)

Degree Program

Biomedical Sciences

First Advisor

Christopher Pearl

Second Advisor

John Capodilupo

Third Advisor

Frank Sylvester

Academic Year



Previous studies in our lab have shown that low dose of supplemental estrogen (1μg) during 15- 18 months prevents the age related loss in sperm production in adult male rats. The purpose of this study is to determine the effects of different doses of supplemental estrogen on a shorter time span (15-16 months) on male reproductive tract during aging. Sprague Dawley rats were divided into four groups of control, 1 μg, 5 μg and 10 μg doses and were treated for one month. The daily sperm production per gram of testis in 5 μg and 10 μg treatment groups were significantly higher than the vehicle, while the 1 μg dose showed no significant change. Sperm counts in the distal cauda were similar between the groups although there was an increasing trend with higher doses. Transit time through distal cauda was similar among the groups. Seminiferous tubule diameter showed significant changes with doses, but they were not biologically relevant. Cauda cell height, tubule and lumen diameter were similar among the groups. Testosterone concentration did not change with the estrogen doses. This suggests that all changes observed were direct results of estrogen treatment. Collectively, our results suggest that 15-16 month treatment with high dose of estrogen increases spermatogenic efficiency in male rats by improving the second phase of spermatogenesis. Cauda epididymis showed no effect of estrogen treatment, although upstream regions might have been affected.

Available for download on Wednesday, July 23, 2025