Immunohistochemical studies in canine prostatic hyperplasia--effect of antiandrogen.

To investigated spontaneous benign prostatic hyperplasia (BPH) in dog the effect of a synthetic steroidal antiandrogen, chlormadinone acetate (CMA) was studied. Old male beagle dogs (5-8 years old) were divided into following experimental groups: group 1 consisted of BPH controls; group 2 received CMA 0.3mg/kg/day p.o., for 6 months. In group 1 animals, glandular hyperplasia of the prostate was clearly detected. The glandular epithelial cells showed uniformly intense immunostaining for nuclear androgen receptors (AR). AR was also localized in the nuclei of the fibro-muscular cells. Immunoreactivity of 5alpha-reductase type I was positive in most glandular epithelial cells. The staining was positive in the cytoplasm but not in the nuclei. No fibro-muscular cells were stained. In contrast, CMA produced marked atrophy of the glandular epithelium. The interacinar fibro-muscular stroma was prominent. Furthermore, immunostaining of nuclear AR of both epithelial and stroma cells was remarkably decreased. The intensity of staining for 5alpha-reductase type I in most glandular epithelial cells also decreased. Interestingly, some basal cells exhibited positive staining for 5alpha-reductase type I. These results indicate that the uptake of testosterone and/or its androgenic effect on the prostate may be suppressed by CMA. We further speculate that the basal cells produce sufficient dihydrotestosterone to maintain themselves even in the presence of low testosterone levels.