Immunocytochemical localization of androgen binding protein in rat Sertoli and epididymal cells.

Abstract

Androgen binding protein (ABP) has been localized in the testis and epididymis using a doublebridge immunoperoxidase technique. In the testis, the intensity of ABP staining and the intracellular localization is dependent on the stage of the spermatogenic cycle. In stages VII and VIII, the immunoreactive ABP was primarily localized in the apical portion of the seminiferous epithelium, with much less staining in the basal area. The most intensely stained material next to the lumen could not be definitely located in Sertoli cells. In stages II–IV, ABP was primarily localized in the basal part of the tubular epithelium with heavy staining around groups of elongated spermatids. In those stages, the ABP staining corresponded to Sertoli cell cytoplasm. The localization of ABP in the base, as well as the apex of the seminiferous tubular epithelium, is consistent with the hypothesis that Sertoli cells secrete into both the basal and adluminal compartments. In the epididymis, the heaviest staining was seen in the proximal caput where immunoreactive material was found in the lumen coating spermatozoa and the brush border of the principal cells. In addition, considerable staining was seen in the epididymal epithelium, with the heaviest staining in the apical portion of the cell. In some cells, however, the entire cytoplasm was immunoreactive. The heavy staining of ABP in the epithelial cells of the first part of the caput epididymis is consistent with a considerable degree of endocytosis of luminal ABP into the epithelial cells, where it is probably degraded. In distal caput, corpus, and cauda epididymides, much less immunoreactive ABP was seen in the lumen and in epithelial cells. The uniform stains of a few cells suggest that transepithelial transport of ABP is possible in this organ.