Ontogeny of mesenchymal androgen receptors in the embryonic mouse mammary gland.
We demonstrate the presence of a high affinity androgen-binding site in the embryonic mouse mammary gland, and describe its appearance and development from the initial formation of the gland bud (day 12) through the androgen-responsive stage (day 14) until term (day 19). Binding assays were done on entire organ rudiments exposed to the ligand [( 3H] testosterone, [3H]5 alpha-dihydrotestosterone, or [3H]methyltrienolone) in vitro, and receptor levels are expressed per gland. In competition experiments, the binding site shows a ligand specificity of a typical rodent androgen receptor. Scatchard analysis yielded a figure of 90-100 million binding sites for one 14-day gland, or approximately 30,000 per target cell. The apparent dissociation constant Kd for ligand binding by the intact tissue was between 0.55 and 0.75 X 10(-9) M. The first binding sites become detectable at the time of mammary bud formation (day 12); their number increases about 20-fold towards the responsive stage (day 14), and they persist at high levels at least until birth. The loss of androgen responsiveness on day 15 is neither accompanied by a loss of receptors nor by a change of their binding affinity.
D000818:Animals; D001665:Binding Sites; D013196:Dihydrotestosterone / Q000378:metabolism; D004963:Estrenes / Q000378:metabolism; D005260:Female; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000196:embryology*; D015741:Metribolone; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D011247:Pregnancy; D011944:Receptors, Androgen / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology; D045165:Testosterone Congeners / Q000378:metabolism
D004963:Estrenes; D011944:Receptors, Androgen; D011987:Receptors, Steroid; D045165:Testosterone Congeners; D013196:Dihydrotestosterone; D015741:Metribolone; D013739:Testosterone