ANTIGEN RETRIEVAL TECHNIQUE UTILIZING CITRATE BUFFER OR UREA SOLUTIONFOR IMMUNOHISTOCHEMICAL DEMONSTRATION OF ANDROGEN RECEPTOR IN FORMALIN-FIXED PARAFFIN SECTIONS

We developed a staining protocol for demonstration of androgen recepto r (AR) in formalin-fixed, paraffin-embedded tissue sections. The metho d is based on the antigen retrieval microwave (MW) heating technique. Results are compared with different types of enzyme digestion pre-trea tments. The strongest immunostaining signal and clearest background we re obtained by MW heating of dewaxed paraffin sections in 5% urea or c itrate buffer solution (pH 6); pure distilled water gave less consiste nt results. Enzymatic digestion with ]pepsin (0.05% in 2 N HCl) for 30 min at room temperature, or trypsin followed by pronase, or pronase d igestion alone, also produced enhanced staining of AR in some cases, b ut there was more nonspecific background, and specific reactivity was less intense. The antigen retrieval MW method can be used to demonstra te AR epitope in prostate tissue after fixation in formalin for as lon g as 7 days. AR immunolocalization was also compared in frozen and par affin sections processed from the same specimen of prostate carcinoma tissue and was found to be qualitatively and quantitatively similar. T his study also provided new information concerning the basic principle s of the antigen retrieval MW method that may be helpful in further de velopment of this technique.