Effect of Estradiol on the Rat Prostate in the Presence and Absence of Testosterone and Pituitary

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Abstract
In an attempt to elucidate the effect of estradiol on the rat prostate, four experiments were conducted. In experiment 1, rats were orchiectomized and were given subcutaneous implants of silastic capsules containing steroid hormones in the following five treatment regimens: empty capsule (C); capsule filled with 2 cm of testosterone (T‐2); T‐2 plus 0.5 cm of e‐tradiol (T‐2 + E‐0.5); T‐2 plus 2 cm of estradiol (T‐2 + E‐2); and T‐2 plus 5 cm of estradiol (T‐2 + E‐5). Three weeks later, no difference was noted in the ventral or the dorsal lobe of the prostate, but the lateral lobe was significantly heavier in animals treated with T‐2 plus various levels of estradiol than in those treated with T‐2 alone. Furthermore, serum levels of both estradiol and prolactin were significantly elevated in the groups treated with estrogen. Rats in experiment 2 were orchiectomized and hypophysectomized and were divided into two groups. One group was treated with T‐2 and another with T‐2 + E‐2. Three weeks later, weights of the three lobes of the prostate were not significantly different between the two groups. Although serum levels of estradiol were significantly higher in the T‐2 + E‐2 group than in the From the Department of Urology, Northwestern University Medical School, Chicago, Illinois T‐2 group, serum levels of prolactin were not significantly different. In experiment 3, rats were orchiectomized and hypophysectomized and were divided into two groups; one received E‐2, while the other received empty capsules. One week later, all three lobes of the prostate in E‐2‐treated animals were significantly heavier than the respective lobes in those receiving empty capsules. However, by three weeks weights of respective lobes were not significantly different between the two groups. To further investigate whether estradiol in the absence of testosterone and the pituitary has any stimulatory effect on the rat prostate, experiment 4 was carried out. Rats were orchiectomized and hypophysectomized; after three weeks, E‐2 or empty capsules were implanted. After one week of treatment with E‐2 or empty capsules, prostatic weights were not significantly different between the two groups. Results indicate that estradiol in the presence of testosterone and the functional pituitary has a stimulatory effect on the growth of the lateral lobe of the rat prostate. This stimulatory effect of estrogen was mediated through the pituitary. In the absence of testosterone and the functional pituitary, estradiol is unable to stimulate prostatic growth; rather, it delays the rate of castration‐induced regression in all three lobes of the rat prostate.