We describe the immunohistochemical detection of the human androgen receptor (AR) in routinely p d , pataffinembedded tissue with the monoclonal antibody (MAb) F39.4. Deparaffrnized d o n s were heated in a microWave oven for antigen retrieval. A panel of human male-and female-derived tissues was investigated. We observed a nuclear staining pattern consistent with previous results on frozen sections. Moreover, we studied the possibility of detecting AR in prolonged formalin-fmed tissue and in paraffin-embedded archival m a t e d . After prolonged fmhtroduction Androgens play an important role in the development and function of the male reproductive system. They mediate their function by binding to the intracellular androgen receptor (AR). Studies on AR distribution in human reproductive and non-reproductive tissues may provide essential information about its role in disease processes that arise in tissues which express the AR.Over the past years, AR distribution in human tissues has been the subject of many immunohistochemical studies (2,4,7,10,13,17). Both polyclonal and monoclonal antibodies (MAb) directed against human AR have been used to visualize the receptor at the cellular level. U e d a et al. (17) studied the immunohistochemical localization of the AR in frozen sections of different tissues, using both MAb and polyclonal antibodies. Ruizeveld de Winter et al. (13) used MAb F39.4 to study AR expression in frozen sections of different human tissues. Kimura et al. (7) investigated the immunohistochemical localization of the AR in paraformaldehyde-fixed, paraffin-embedded human tissues with a polyclonal antibody. In the latter study, decreased or absent immunoreactivity was found (12) studied the immunohistochemical identification of the AR in germ cell neoplasia using MAb ANI-15 and F39.4 on frozen and formalin-fixed tissue. Both antibodies showed a positive reaction on frozen sections. However, on paraffii sections, MAb F39.4 showed no reaction and MAb ANI-15 showed strong nuclear immunoreactivity of all testicular nuclei including lymphocytes, suggesting the possibility of a nonspecific reaction. Recently, Nakada et al. (11) were able to detect the AR in neuroendocrine cells in Amexprocessed (14) but not in formalin-fixed, paraffin-embedded human prostate tissue with MAb AN1-15.Until recently, to our knowledge, it has been impossible to detect the human AR in routinely formalin-fixed, paraffin-embedded tissue with an MAb. This is of great advantage because of the highly consistent specificity of MAb in combination with the optimal morphology achieved in paraffii sections and the possibility of reuospective studies. The present study describes the detection of human AR with MAb F39.4 in routinely formalin-fued, paraffin-embedded tissue, after a simple antigen retrieval treatment (16). A panel of human male-and female-derived tissues was investigated for the presence and distribution of the AR. The results were compared 1169

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