Androgens drive spermatogenesis by processes that are largely unknown. Direct effects on germ cells and indirect effects mediated via testicular somatic elements are currently under consideration, and specific localization of
androgens in seminiferous tubules may provide information as regards this. Adult male rats were injected with
ethane dimethanesulfonate (EDS; 75 mg/kg
body weight) or vehicle. Testes were fixed and
paraffin-embedded for localization of
testosterone immunoreactivity 1 and 2 weeks
after treatment, using the unlabeled antibody (PAP) technique. Plasma
testosterone dropped from a pre-treatment level of 2.3 ng/ml to below 0.2 ng/ml 3 days after EDS injection and remained at low levels until the end of observation, accompanied by a progressive decrease in testicular weight. In the seminiferous tubules of vehicle-injected males,
testosterone immunoreactivity was found in nuclei of spermatocytes and spermatids and in nuclei and the cytoplasm of Sertoli cells, and showed typical variations according to the stage of spermatogenesis. One week after EDS treatment, immunoreactivity had disappeared from the seminiferous epithelium. Two weeks
after treatment, staining of germ cells was detected in two out of four males. The disappearance and reappearance of immunoreactivity coincided with the time course of EDS effects on rat Leydig cells, and we conclude that it corresponds to
androgen specifically localized in fixed,
paraffin-embedded tissue. Because staining of germ cell nuclei varied with the stage of spermatogenesis, the technique may detect a physiologically relevant
androgen fraction; its location suggests that
androgens may also directly affect certain germ cell stages.