BACKGROUND.
Organ culture methods have long been used in the study of the prostate because effects of drugs and hormones can be examined in the absence of systemic effects. METHODS. Neonatal rat ventral prostates (VP) were grown on Millipore filters floating on fluid medium composed of Dulbecco's modified Eagle's medium/Ham's F-12 supplemented with insulin, transferrin, and hydrocortisone, and in the presence or absence of testosterone (T, 10 -8 M). RESULTS. In the presence of T, ductal lumen formation occurred, ductal branching was extensive, and basal and luminal epithelial cells were identified by immunocytochemistry based on their distinctive cytokeratin profile. In the absence of T, ductal lumen formation did not occur, basal and luminal epithelial cells failed to differentiate, and there was a marked decrease in prostatic organ size relative to glands grown with T. Interestingly, DNA synthesis, as measured by counts per min (CPM) for 3 H-thymidine incorporation, showed that DNA synthesis per g DNA at 7 days of organ culture was not inhibited by lack of T. Androgen receptor expression is another marker of prostatic epithelial differentiation, and it occurred in both the presence and absence of T. CONCLUSIONS. Growth and differentiation of the neonatal rat prostate in vitro occur in a manner similar to that of the developing prostate in vivo, demonstrating that organ cultures of neonatal rat ventral prostates provide a faithful model for studying rat prostatic development and differentiation under serum-free conditions.