Effects of prolactin on DNA synthesis and growth of the accessory sex organs in male mice.

The role of PRL in the development of male accessory sex organs remains unresolved. In the present studies, the influence of PRL and testosterone upon DNA synthesis and cell proliferation was examined in the anterior prostate gland (AP) and the seminal vesicles (SV) of mice. Hormonal effects on DNA synthesis were evaluated by examining the in vitro incorporation of [3H]thymidine into DNA in relation to temporal alterations in tissue DNA content. In intact mice, PRL (300 IU/kg daily) produced peak stimulation of [3H]thymidine incorporation into DNA by SV after 3 days of treatment. In contrast, PRL failed to alter [3H]thymidine incorporation by the AP. Only in SV did PRL injections lead to elevated levels of tissue DNA. Injections of testosterone (0.75 or 7.5 mg/kg daily for 3 days) to castrated mice also produced significant stimulation of labeled thymidine incorporation into DNA by AP and SV. Concomitant injections of PRL (150 IU/kg) and testosterone (0.75 or 7.5 mg/kg) enhanced the stimulatory effects of this androgen on DNA synthesis and DNA content in the SV, but not in the AP. When PRL alone was administered to castrated mice, it failed to affect either [3H]thymidine incorporation into DNA by AP and SV or accessory sex organ weights and DNA contents. The results of these studies suggest that PRL enhances the effects of androgens upon DNA synthesis and growth of the seminal vesicles, but not of the anterior prostate glands of mice.