Figure 5

Both 17-β-estradiol and progesterone induce morphologic responses in the prepubertal mammary gland. Prepubertal 3-week-old BALB/c mice were OVX, allowed to recover for 2 weeks, and then treated once with vehicle control (C), E2, P, or E2+P, as described in the Materials and Methods section. (A) End bud (EB) formation in response to C, E2, and P. Inset shows higher magnification of EB. Note similar EB formation after E2 or P treatments. Scale bar, 1 mm. (B) PR expression. Immunofluorescent detection of PR-positive luminal cells. The values represent the mean ± SEM percentage of PR-positive cells (n = 3 animals per treatment).