Induction of androgen receptor formation by epithelium-mesenchyme interaction in embryonic mouse mammary gland.

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Abstract
The role of tissue interaction in the development of hormone responsiveness was studied in the embryonic mammary gland of the mouse, which becomes sensitive to testosterone on day 14. Previously the mesenchyme was identified as the sole target for the hormone, although it was also demonstrated that its response to testosterone required the presence of mammary epithelium. Using autoradiography, [3H]testosterone or [3H]5.alpha.-dihydrotestosterone was shown to be bound only by those mesenchymal cells closest to the epithelial mammary bud. When mammary epithelia were experimentally associated with mesenchyme of the mammary region and cultured together for 3 days in vitro, they also became surrounded by several layers of [3H]testosterone-binding mesenchymal cells. This tissue association was accompanied by a substantial increase of androgen-binding sites in the explants. No hormone-binding mesenchymal cells were seen in combinations with epidermis or pancreas epithelium; only salivary epithelium showed a weak positive effect. Mammary epithelium apparently induces the formation of androgen receptors in adjacent mesenchyme and thus controls the development of androgen responsiveness in this tissue.