IMMUNOHISTOCHEMICAL LOCALIZATION OF ANDROGEN RECEPTORS IN THE RAT TESTIS - EVIDENCE FOR STAGE-DEPENDENT EXPRESSION AND REGULATION BY ANDROGENS

Androgens are essential for the maintenance of normal spermatogenesis in the rat. We assessed the sites, developmental pattern, and hormonal control of androgen receptors (AR) in the rat testis. Adult male rats were studied after 1) no treatment; 2) ethane dimethane sulfonate (ED S), which eradicates Leydig cells and endogenous testosterone (T); 3) EDS plus T replacement beginning at the time of EDS administration; or 4) methoxyacetic acid, which leads to the loss of specific germ cell types. Testes were also obtained from normal immature rats (aged 5, 14 , 16, 21, 28, 31, 35, 38, and 45 days). After microwave antigen retrie val, immunohistochemistry was performed using a rabbit polyclonal anti body (Novocastra) raised against a peptide unique to the N-terminal re gion of the AR and detection with biotinylated swine antirabbit immuno globulin G, avidin-biotin complex/ alkaline phosphatase, and nitroblue tetrazolium salt (NBT)/5 bromo-4-chloro-3-indolylphosphate (BCIP) sub strate. In adults, nuclear immunostaining of Sertoli cells (SC) increa sed progressively in intensity from stages II through VII of the sperm atogenic cycle, and then declined precipitously during stage VIII to b ecome barely detectable in stages IX-XIII. Prominent AR immunostaining was also evident in peritubular myoid cells, arterioles, and intersti tial cells; staining in these cells did not vary with the stage of the cycle of the adjacent tubules. EDS caused a severe loss of AR immunos taining in all cell types. Replacement of T in EDS-treated animals res ulted in a pattern of AR immunostaining comparable to that in controls , although staining intensity was reduced. Methoxyacetic acid administ ration did not affect the pattern of AR staining. In immature rats, pe ritubular myoid cell immunostaining was prominent from day 5; SC stain ing was detectable on day 5, increased in intensity with age, and beca me stage dependent between days 21-35. The following conclusions were reached. 1) Immunohistochemically detectable AR expression in SC occur s predominantly in stages II-VII of the spermatogenic cycle, with high est levels at stage VII. 2) AR immunostaining is also prominent in per itubular myoid cells, arterioles, and Leydig cells (but not in germ ce lls), but is unrelated to the stage of adjacent tubules. 3) Endogenous T and/or its metabolites control the expression of AR in the testis. 4) AR immunostaining is detectable by day 5 of age and becomes stage s pecific in SC between days 21-35.