Endocrine Abstracts

It is not surprising that mouse prostate gland is anatomically very similar to that in the rat, which consists of the ventral prostate (VP), dorsolateral prostate (DLP) and anterior prostate (AP). However, the basic biological function of the prostate, prostatic secretion, has been suggested to be diverse between the two species and yet poorly understood. We have identified major secreted proteins from separate prostate lobes of the mouse as well as the rat by mass spectrometric analysis. Hormone dependency of these protein mRNAs was also examined in both species. In mice, the VP secretes spermine binding protein, serine protease inhibitor KT3 and a 91 kDa hypothetical scavenger receptor, while the DLP/AP secrete a protein similar to immunoglublin binding protein (IgBPLP) and experimental autoimmune prostatitis antigen protein 2 (EAPA2). Prostate secretion in mice was very different from that in rats being only IgBPLP and PSP94 in common. Castration of animals led to a decrease in the mRNAs of these secreted proteins. In rats, a quick androgen response was apparent in the VP as compared with other lobes. In the mouse, however, large decreases in mRNAs were evident in all of the lobes. Combined administration of androgen and estrogen showed synergistic effects on prostate secretion in rats but not in the mouse case. The present study has provided an understanding of the major secretory function of the mouse prostate, and has identified common aspects of secretory functionality between mouse, rat and human. The identified secretory proteins should be available as models of androgen-dependent gene regulation and are candidates as markers for prostatic differentiation. Some of the identified proteins may be useful as pathological markers associated with prostate disorders.