IMMUNOLOCALIZATION OF ANDROGEN RECEPTOR TO INTERSTITIAL-CELLS IN FETAL-RAT TESTES AND TO MESENCHYMAL AND EPITHELIAL-CELLS OF ASSOCIATED DUCTS

Androgens are required for the development of male internal and extern al genitalia. Androgen action is mediated by an intracellular receptor which acts as a transcription factor following activation by ligand b inding. The aim of the present study was to define the time of appeara nce of androgen receptor (AR) in the male fetal rat gonad using immuno histochemistry. Intact fetuses (days 13.5-16.5) or testicular tissue ( days 16.5-20.5 and days 3-7 postnatal) were fixed in Bouins' solution and processed into paraffin wax. On day 16.5 nuclear AR were present i n mesenchymal cells surrounding the Wolffian duct but those around the Mullerian duct were receptor negative. During the following day (17-1 8) the abundance of nuclear staining increased, becoming detectable in the epithelial cells of the Wolffian ducts. Within the testis some nu clear staining was apparent at day 17 but was confined to interstitial cells surrounding the seminiferous cords. As development of the testi s proceeded the abundance of nuclear AR in peritubular and elongated m esenchymal cells increased. AR were not detected in fetal Leydig cells expressing 3 beta-hydroxysteroid dehydrogenase nor in the ovaries or associated ducts of female fetuses at the same ages. In conclusion, in the rat we have found AR expression detectable by immunohistochemistr y in mesonephric mesenchyme to be confined to that underlying the Wolf fian ducts and to be absent from the area around the degenerating Mull erian duct. On and after day 17 of gestation AR is present in Wolffian duct epithelial cell nuclei and within the testis it is confined to p eritubular and interstitial cells which may have migrated from the mes onephros. Fetal Leydig cells were receptor negative. Within the semini ferous cords AR in Sertoli cells remained low until after birth and so me perinuclear staining was detected in cells thought to be gonocytes. We believe this to be the first report of immunolocalisation of AR to fetal testicular interstitial cells.