MORPHOGENETIC AND PROLIFERATIVE EFFECTS OF TESTOSTERONE AND INSULIN ON THE NEONATAL MOUSE SEMINAL-VESICLE INVITRO

Effects of testosterone (T) and insulin on epithelial branching morphogenesis were investigated in cultured seminal vesicles (SVs) of neonatal mice. SVs from 0-day-old male mice were cultured for 0.5-6 days in serum-free chemically defined medium in the presence of T (10(-7) M), insulin (10-mu-g/ml), or T plus insulin or in medium lacking both hormones. Without the addition of both hormones, SVs failed to grow, based on DNA and protein contents, and did not show any epithelial branching morphogenesis. T induced a 2.5-fold increase in protein content in SVs cultured for 6 days and elicited modest epithelial branching morphogenesis. Insulin increased the protein content of cultured SV rudiments as much as T, but failed to elicit epithelial branching morphogenesis. The combination of both hormones induced a 4.3-fold increase in protein content in cultured SVs and elicited more extensive epithelial branching morphogenesis than T alone. Epithelial and mesenchymal DNA contents in SVs declined slightly during the first 12 h of culture in all treatment groups. The epithelial DNA content in SVs grown with insulin alone remained constant thereafter, while that of SVs grown with T alone or in combination with insulin increased 1.2- and 2.6-fold, respectively. In the absence of both hormones, the mesenchymal DNA content remained constant in SVs grown for 6 days after the initial decline in DNA content. In contrast, mesenchymal DNA content was increased to the same degree (1.4-fold) by either T or insulin alone or in combination. The labeling index with [H-3]thymidine of SV epithelium and mesenchyme grown under the hormonal conditions described above corroborated the results of epithelial and mesenchymal DNA contents. These data indicate that insulin by itself has no effect on epithelial proliferation and branching morphogenesis in the neonatal mouse SV, but, instead, amplifies the morphogenetic and proliferative effects of androgen on the developing mouse SV, thus eliciting extensive branching morphogenesis. Both insulin and T have a slight (nonsynergistic) effect on proliferation of SV mesenchyme. Analysis of androgen metabolism in developing mouse SVs indicated that dihydrotestosterone was the major product when T was used as substrate in SVs grown under all hormonal conditions. The rate of DHT production per 100 mg protein was not significantly different among the different treatment groups. Higher levels of 5-alpha-androstane-3-alpha,17-beta-diol were detected in SVs grown in the absence vs. the presence of T regardless of the presence or absence of insulin. Therefore, the synergistic effect of insulin on androgen-induced epithelial proliferation and branching morphogenesis of the neonatal mouse SV was not caused by enhanced production of dihydrotestosterone, the major androgen triggering the postnatal development of the mouse SV.