Effects of Exogenous Estrogen and Testosterone on Reproductive Structures and Spermotogenesis in the Male Rat

Abstract

The steroid hormones estrogen and testosterone are essential in the development and maintenance of male reproductive structures. Testosterone is necessary for maintenance of male reproductive structures and for normal spermatogenesis, acting on Sertoli cells to provide the proper environment for healthy spermatid production. Aromatase converts testosterone into estrogen in testicular germ cells and epididymal sperm. This testicular and epididymal estrogen plays a vital role in maintaining proper fluid dynamics within the male reproductive tract. This study sought to determine how exogenous steroid hormones affected male reproductive structures (testes and seminal vesicles) and spermatogenesis in adult male Sprague-Dawley rats. Rats were divided into two treatment groups: half were gonadectomized (GDX) and half underwent a sham gonadectomy (intact males). All rats were implanted with one of three silastic implants at the time of their surgery. Implants contained either estradiol (E2), testosterone (T), or were empty (a sham implant). After 20 days, the rats were sacrificed and testicular (intact only) and seminal vesicle weights and lengths were measured. Brd-U was used to visualize mitotic division and thus provide a measure of spermatogenesis. Intact males given either T or E2 showed a significant decrease in gonad weight. Seminal vesicles in the E2 treatment group were drastically smaller but similar in size to the sham implant GDX rats. This suggests that the reproductive system of the adult male rat may be more responsive and sensitive to fluctuating levels of estrogen than previously thought.