Immunolocalization of androgen receptor in canine prostatic hyperplasia--effect of antiandrogen

The effect of a synthetic steroidal anti-androgen, chlormadinone acetate (CMA), on spontaneous benign prostatic hyperplasia (BPH) in the dog was investigated. Old male beagle dogs (5 to 8 years old) were divided into the following experimental groups: group 1 consisting of BPH controls, and group 2 which received CMA of 0.3 mg/kg/day orally for 6 months. In group 1, glandular hyperplasia of the prostate was clearly observed. The glandular epithelial cells showed uniformly intense nuclear immunostaining for androgen receptor (AR). In contrast, CMA produced marked atrophy of the glandular epithelium. The interacinar fibromuscular stroma was prominent. Furthermore, nuclear immunostaining for AR in both epithelial and stroma cells was remarkably decreased. These results indicate that the uptake of testosterone and/or its androgenic effect on the prostate may be suppressed by CMA. The decreased AR-immunostaining may be explained by the decrease in the number of AR and/or antibody binding sites for AR.