Androgen stimulation of prolactin receptors in rat prostate

Specific receptors for iodine-labelled human prolactin ([125I]hPrl) are present in membrane preparations of the rat ventral prostate. The binding is saturable with an apparent association constant (Ka) of 2.2 X 10(9) M-1 and a binding capacity of about 1 pmol/100mg prostatic tissue. The binding of [125I]hPrl is inhibited by hPrl, ovine Prl (otprl) and human growth hormone, but not by ovine FSH or LH. Serum from rats having Prl-producing pituitary tumors caused a displacement of the [125I]hPrl from the receptors, and the displacement curve was parallel with that of the hPrl standard. Treatment of immature rats with varying doses of dihydrotestosterone propionate (10-5000 microng) causes a dose-dependent stimulation of Prl receptors calculated both as binding sites per mg of membrane protein and as binding sites per prostate. Androgen stimulation of prostatic Prl receptors increases the tissue sensitivity for circulating Prl and may be one reason for the known increases in endogenous cAMP levels in prostatic tissue after androgen treatment in vivo.