Sex steroid imprinting of the immature prostate. Long-term effects

New periods of sex hormone sensitivity in the life cycle of the male rat that occur before the onset of sexual maturation and that determine subsequent responsiveness and growth of the adult prostate have been elucidated. If high doses of estrogen (17 beta-estradiol--500 microgram per day, or estradiol benzoate--250 micrograms per day, or estradiol dipropionate--100 micrograms per day) are administered to intact male rats for 2 days during the 1st week after birth, the prostate, at adulthood, is diminutive in size and is inert to the action of exogenous androgens. In contrast, lower doses of estrogen (17 beta estradiol--100 micrograms per day) administered at 20 and 22 days of age enhance the sensitivity of the adult prostate to testosterone by approximately 50 per cent. Furthermore, it has been determined that continued testicular function is required up to the time of puberty for full prostatic growth.