Effects of Hypophysectomy and Prolactin Replacement Therapy on Prostatic Response to Androgen in Orchiectomized Rats

When rats castrated on Day minus 23 (D-23) are hypophysectomized (D-13) and treated with testosterone propionate (1.0 mg every other day for 16 days; (D-0 is the first day of testosterone propionate treatment) the body weight, prostatic weight and citric acid level of the prostate decrease more than those of testosterone-treated, castrated, sham-hypophysectomized rats. Such observations imply the involvement of a pituitary factor in the maintenance of prostatic integrity. More direct evidence is obtained when prolactin replacement therapy (50 units daily for the last 13 days) in hypophysectomized, castrated, testosterone-treated rats increases the prostatic weight and both content and concentration of citric acid significantly and the body weight slightly. Thus, the results of our in vivo experiments confirm the important observations of Grayhack and his coworkers that a) the prostatic response to androgen in hypophysectomized, castrated rats is less than that of castrated rats with the pituitary gland intact and b) prolactin acts synergistically with testosterone in promoting growth and increasing weight and citric acid concentration in the prostate. Our results, moreover, show direct effects of both hypophysectomy and prolactin replacement therapy on the ventral lobe of the prostate as well as the dorsolateral lobe.