3D serial section reconstruction of the UGS from GD-19 mice exposed to a high dose (200 μg/kg per day) of DES from GD 14–18 (A), compared with vehicle-treated controls (B). Reconstructions are shown from the caudal–dorsal perspective in the left images and caudal–dorsolateral on the right. Exposure of pregnant females to this DES dose resulted in the inhibition (*) of dorsal (DP, green) and lateral (LP, yellow) prostate ducts and coagulating glands (CG, dark blue). There is an abnormal pattern of development in ventral duct formation (VP, light blue). The utricle (Ut, pink) was present in oil controls only as a small remnant of the Müllerian ducts, whereas these ducts did not regress in the DES-exposed males. DES also resulted in a decrease in the size of the seminal vesicles (SV, purple). VD, vas deferens, U, urethra. (Scale bar, 100 μm.)

3D serial section reconstruction of the UGS from GD-19 mice exposed to low doses of estrogenic chemicals, DES, bisphenol A, and ethinylestradiol, during fetal development. The UGS depicted for each treatment was closest to the group mean for prostate duct number and size. All images are viewed from a left-lateral perspective. (A) Shown are the differences in patterns of prostate ductal development after fetal exposure to these chemicals, compared with oil-treated controls. There is a significant increase in the total number of ducts in estrogen-treated animals and a corresponding increase in overall prostate volume. (B) Shown is the marked alteration in the shape of the urethra (U, red) in the region of the bladder neck (BN), which is markedly constricted (*) inthe mice exposed to the estrogenic chemicals, compared with controls. In addition, the region of the UGS (the prostatic sulcus or colliculus, arrow) associated with the development of the dorsal (DP, green) and lateral (LP, yellow) prostate ducts is enlarged, particularly by bisphenol A, compared with controls. Ventral prostate (VP, light blue). (Scale bar, 100 μm.)

Immunohistochemical localization of PCNA in developing dorsolateral prostate ducts (DLP) of the UGS of GD-19 fetal mice. (A–D) Representative sections of comparable regions are shown for oil-treated control mice (A) and animals exposed to the estrogenic compounds DES (0.1 μg/kg per day) (B), bisphenol A (10 μg/kg per day) (C), and ethinylestradiol (0.1 μg/kg per day) (D). In each of the groups studied, the predominant site of PCNA staining was associated with the proximal region of the longest ducts. In D, the Inset is a digitally enhanced image of developing prostate duct [PCNA-stained cells (brown) vs. nonstained cells (blue)]. These proliferating cells were continuous with the basal layer of urothelial epithelial cells in the urethra (U). PCNA was not detected at the distal tips of the longest ducts that are juxtaposed to a condensation of mesenchyme (D; area with *). This region of mesenchyme is associated with induction of postnatal branching morphogenesis, after which formation of a ductal lumen and development of differentiated, secretory epithelial cells occurs. A negative immunohistochemistry control section is shown in A Inset. A comparison of cellular proliferation in these experimental groups is presented in Table 1. (Scale bar, 50 μm.) (E) Immunohistochemical localization of MK5, a marker for basal epithelial cells, in the developing prostate ducts of an oil-treated control GD-19 mouse fetus. The majority of labeled cells are found in the proximal region of the developing ducts (DP, dorsal prostate) and the basal epithelial cells of the urethra (U). The initial duct formation is associated with periurethral mesenchyme (M). Cells in the distal portion of the duct are infrequently stained. The latter region is juxtaposed to a condensation of mesenchyme (*). The pattern of staining seen with this antibody closely resembles the pattern seen for PCNA staining. (Scale bar, 20 μm.)