Effect of a new 5α-reductase inhibitor on size, histologic characteristics, and androgen concentrations of the canine prostate

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Abstract
Mature male beagles were used in studies designed to determine the effect of the steroidal 5α‐reductase inhibitor 17β‐N,N‐diethylcarbamoyl‐4‐aza‐4‐methyl‐5α‐androstan‐3‐one (4‐MA) on size, histology, and androgen concentration of the prostate. Subcutaneous administration of 3 or 15 mg/kg/day for 43 days caused a sharp decline in prostate volume, flattening of prostatic epithelial cells, vacuolization of the cytoplasm and pycnosis of the nuclei. Whereas serum testosterone levels remained normal in dogs injected with 3 mg/kg/day, they were lower in those that received 15 mg/kg/day. Concentrations of both testosterone and 5α‐dihydrotestosterone were reduced in the prostates of dogs that had received either 3 or 15 mg/kg/day of 4‐MA. The 15 mg/kg/day level also appeared to adversely affect spermatogenesis. In a 43‐day study, 4‐MA given orally once each day at levels of 0.1, 0.3, or 1 mg/kg failed to cause a significant decrease in prostate volume. However, daily divided oral doses totaling 1 or 3 mg/kg were given in a 42‐day test and both treatment levels produced significant reductions in prostate size.