Study of the effect of an anti-androgen (oxendolone) on experimentally induced canine prostatic hyperplasia. I. Morphological analysis.

To investigate the effect of anti-androgens on BPH, Oxendolone (OXD), a pure anti-androgen, was tested in experimentally induced BPH in 17 beagle dogs, alone or in combination with medroxyprogesterone acetate (MPA) which displays both anti-androgenic and anti-estrogenic activity. The relatively early stage of canine BPH was induced by administration of 3 alpha-androstanediol (3 alpha-A) plus estradiol (E2) for 6 months and followed by testosterone propionate (TP) plus E2 for another 6 months during the anti-androgenic treatment. By the manipulation with T, a decrease in volume of glandular component associated with a relative increase in stromal tissue was achieved, which mimics human BPH histology. The prostate substituted with T and E2, however, gradually decreased in size. Therefore the effect of OXD or OXD + MPA was not significant against the untreated controls (T-E control). The weight of the prostate in these OXD +/- MPA groups was however significantly reduced as compared to that of BPH controls which received 3 alpha-A and E2 throughout the experimental period. On histological examination, atrophic changes were observed in the hormone-treated groups compared to the T-E control. The finding was the most striking in the OXD + MPA group with small non-involuted acini scattered in the abundant stomal tissue. This was almost identical to the appearances of castrated control groups. Atrophy may be due not only to the anti-androgenic but also to the anti-estrogenic property of MPA. A report on the hormonal background of this experiment will appear in the second article.