Development and loss of androgen responsiveness in the embryonic rudiment of the mouse mammary gland

The androgen-responsive phase in the development of the mammary gland was determined by exposing rudiments of various developmental stages to testosterone in vitro. Although testosterone causes destruction of the mammary epithelium in 14-day male fetuses, it failed to prevent formation of mammary buds in explanted 11-day skin. It was found that mammary rudiments become responsive to androgens only late in Day 13 of gestation, and that they are no longer responsive on Day 15 and later. Both acquisition and loss of androgen responsiveness do occur on time in explanted glands, indicating intrinsic developmental changes in the rudiment. The experiments and their results are schematically summarized in Fig. 2.