Immunocytochemical localization of androgen-binding protein in the male rat reproductive tract

The localization of androgen-binding protein (ABP) in the reproductive tract of young adult male rats was studied with the peroxidase-antiperoxidase technique using frozen sections and light microscopy. Within the seminiferous tubules, a positive reaction was noted in the apical portion of the epithelium, apparently in spermatids and/or Sertoli cells. ABP was localized in granules in the apical cytoplasm of the principal epithelial cells of the proximal part of the caput epididymis and in the epithelial cells of the ductuli efferentes. The cells in the distal part of the caput as well as the corpus and cauda of the epididymis did not contain ABP. Numerous coated vesicles and multivesicular bodies were present in the supranuclear cytoplasm of the epididymal epithelium where ABP was taken up. The results indicate that ABP is taken up from the lumen by epithelial cells of the ductuli efferentes and proximal part of the caput epididymis.