Immunohistochemical and in-situ hybridization analysis of androgen receptor expression during the development of the mouse prostate gland.

Ontogeny of the androgen receptor in the mouse prostate during fetal and post-natal periods was re-evaluated by histochemistry using a monoclonal antibody and by in-situ hybridization using a cDNA probe. Unlike steroid autoradiographic techniques which show ligand-binding sites in autoradiographs, these two techniques make it possible to investigate the expression of receptor protein and the transcription of its mRNA directly at the cellular level. Our previous autoradiographic data have demonstrated that only the mesenchyme takes up androgen during the fetal period; no incorporation of androgen by the epithelium has been observed in the fetus, although this does occur in later development. This observation indicated that the morphogenesis of prostatic epithelium is induced by the androgen-activated surrounding mesenchyme. In the post-natal prostate, the present data are nearly the same as those obtained by autoradiographic techniques; ligand-binding activity and expression of the receptor and its mRNA are much higher in the epithelium than in the stroma. On the other hand, the present study indicated that the fetal epithelium, which had shown no ligand-binding activity by autoradiographic analysis, expressed the same amount of receptor protein and its mRNA as the fetal mesenchyme. The results suggest that androgen receptor protein is expressed in the fetal epithelium but may not be able to bind to androgens until post-natal development.