Differential distribution of dihydrotestosterone and estradiol binding sites in the epididymis of the mouse. An autoradiographic study.

The distribution of androgen and estrogen binding sites in the mouse epididymis was assessed by autoradiography with 3H dihydrotestosterone (3H DHT) and 3H estradiol (3H E2). Nuclear labeling with 3H DHT in principal cells of the epithelium is high in the caput, low in the corpus, and high again in the cauda. 3H E2 also binds to the nuclei of principal cells. The pattern is distinct from 3H DHT: nuclear labeling is highest in the ductulus efferens and high in the caput, but low or absent in corpus and cauda. Apical cells in caput and clear cells in corpus and cauda are moderately labeled with 3H DHT but heavily labeled with 3H E2. Connective tissue cells show variable labeling with both hormones, being more pronounced with 3H E2. Smooth muscle cells are also labeled to varying degrees with both hormones. The different binding patterns of 3H DHT and 3H E2 and the results of the competition studies with unlabeled compounds demonstrate that in the epididymis besides the specific nuclear receptors for androgen also estrogen receptors are present.