Antibodies against synthetic peptides recognize the human and rat androgen receptor

Antibodies against two synthetic peptides (aa 299-311 and aa 544-559) selected in different immunogenic domains of the human AR, were induced in rabbits. Antiserum reactivity against the native receptor was investigated by gel permeation chromatography and sucrose density gradient centrifugation using [3H]mibolerone-labeled rat prostate cytosol and [3H]5 alpha-dihydrotestosterone-labeled T-47D cytosol as a source of AR. The absence of cross-reactivity of the antisera with estrogen, progesterone and glucocorticoid receptor was confirmed by density gradient centrifugation of rat uterus cytosol labeled with [3H]E2 or [3H]ORG 2058 and rat liver cytosol labeled with [3H]dexamethasone. After partial proteolytic breakdown of rat prostate AR by endogenous proteases the steroid-labeled receptor was recognized only by the second peptide (aa 544-559) antibody. This proteolytic breakdown could be prevented to a large degree by addition of a high concentration of soybean trypsin inhibitor. The specific AR antibodies provide new tools for the functional analysis of AR, since they interact selectively with specific domains of the receptor.