Figure 4

Cellular localization and ovarian steroid regulation of α₅β₁ integrin in mouse mammary glands during development. (a) Frozen sections of mammary glands from immature, pubertal, sexually mature (3-, 5-, 10-week-old, respectively), early pregnant (9–12 days), late pregnant (19–21 days) and lactating (7–10 days) mice were immunostained with antibody to the α₅β₁ integrin. Note that staining is seen around ducts at 5 and 10 weeks of age and around alveoli in early pregnant mice. No staining was seen at 3 weeks of age or at late pregnancy and lactation. Mag. 100X. (b) Mammary glands were removed from 10-week-old mice that were ovary intact (intact), ovariectomized for 1 week (OVX), or OVX given a single i.p. injection containing 17β-estradiol (1 μg) + progesterone (1 mg) (E + P) and sacrificed 24, 48 or 72 hour later. Frozen sections were stained with antibody to α₅β₁ integrin and fluorescence staining intensity (measured as average pixel brightness) was quantitated [20]. ^* P < 0.05 that OVX α₅β₁ integrin staining intensity is lower than intact. ^** P < 0.05 that at 24, 48, and 72 hr post E + P injection, α₅β₁ integrin staining intensity is greater than OVX.