A model for studies on the response of the ventral prostate to oestrogens
Abstract. The effects of oestrogen administration on the weight of ventral and dorsolateral prostates were studied in castrated rats of Wistar-Furth and Copenhagen strains. Direct effect of oestradiol (Oe2) on prostatic tissue was also investigated in organ culture. Oe2-treated animals received daily injections of 50 μg for 7 days. Control animals were treated with the vehicle only (peanut oil). In 4 month old Copenhagen rats the mean weight of the ventral prostates (42.4 ± 9.4 mg/100 g body weight) was significantly higher than that in the control animals (19.9 ± 4.6 mg/100 g body weight, P < 0.0001). No such differences were observed in older Copenhagen rats (9 months old) or Wistar-Furth rats (3 and 6 months old). Thus, this effect of Oe2 on ventral prostate seems both strain specific and age specific. Similar strain and age differences in the Oe2 effect were found in the dorsolateral prostate, but to a smaller extent. Direct interaction of Oe2 with target tissue was demonstrated in culture as evidenced by the ability of the steroid to prevent regression in explants derived from prostates of Copenhagen rats. The in vivo effects of Oe2 on the prostate weights could not be explained by differences in specific androgen or oestrogen receptor contents or in testosterone (T) metabolism. However, the prostates of younger Copenhagen rats differed from those of all other groups in three respects: 1) they contained high levels of oestramustine binding protein (OeBP), 2) they had the highest amount of uptake of radioactivity into the nuclear residue, and 3) their histological picture was characterized by diffuse stromal architecture having the appearance of oedematous tissue.