Fig. 8. Response of mammary glands from wild-type and Vdr knockout to exogenous hormones. Representative wholemounts of mammary glands removed from wild-type (A,C,E) and Vdr knockout (B,D,F) mice before and after estrogen plus progesterone supplementation. Wholemounts shown in A (wild-type) and B (Vdr knockout) are representative of glands removed from 5-week-old animals that were not supplemented with estrogen and progesterone. Wholemounts shown in C (wild-type) and D (Vdr knockout) represent glands removed at 5 weeks of age after 15 days in vivo supplementation with estrogen and progesterone via subcutaneous pellets. Glands shown in E (wild-type) and F (Vdr knockout) are the contralateral glands to those shown in C (wild-type) and D (Vdr knockout), which were removed after 15 days in vivo supplementation with estrogen and progesterone and placed in organ culture in the presence of estrogen, progesterone and lactogenic hormones for 10 additional days. Arrows indicate alveolar growth and side branching in D and undeveloped ducts in C. Images are representative of 10 glands per genotype examined. Scale bar: 500 µm.