Androgen receptor distribution in adult human testis

The distribution of the androgen receptor (AR) in archival human testes was determined immunocytochemically using an affinity-purified peptide-specifi c rabbit antibody, PG21, and employing a modified biotin-streptavidin-immun operoxidase method that incorporated a biotin amplification step. In combin ation with microwave epitope retrieval, the biotin amplification step incre ased the sensitivity of the immunostaining assay approximately 20-fold. Thu s, the useful range at which PG21 rendered a robust, specific immunostainin g signal without also increasing nonspecific background was extended dramat ically. Broadening the useful range of the PG21 antibody made it possible t o resolve the relative amounts of immunopositive AR in different cell types of the human testis. At a high PG21 concentration, for example, all AR-pos itive cells exhibited a robust immunostaining intensity, but it was not pos sible to distinguish between nuclei exhibiting either high or moderate immu nostaining intensities. In contrast, as the concentration of PG21 was decre ased, distinct populations of testicular cells exhibited differential AR im munostaining intensities in their nuclei. AR immunostaining of Sertoli cell nuclei was present at low PG21 concentrations at which no immunostaining o f peritubular myoid cells or Leydig cells could be detected. In turn, AR im munostaining of peritubular myoid cells was detected at PG21 concentrations that did not immunostain Leydig cells. Moreover, within the seminiferous e pithelium, Sertoli cell nuclear AR staining intensity was less at stages V and VI of the cycle of the seminiferous epithelium than that at stage III, and stage III staining intensity was greater than that at stages I and II. This AR immunostaining pattern in human Sertoli cell nuclei as a function o f the cycle of the seminiferous epithelium is reminiscent of the pattern ob served in rodent species. Finally, no AR immunostaining of germ cells was o bserved at any of the PG21 concentrations examined.