Reversible long-term toxicity of epristeride in beagle dogs

Epristeride (17beta-N-t-butylcarboxamide-androst-3, 5-diene-3-carboxylic acid) is an uncompetitive inhibitor of steroid 5alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT), and has been shown to retard the growth of hyperplastic prostates. The objective of the current investigation was to research the toxic effects of epristeride and to demonstrate its reversible. In the experiment, 18 beagle dogs (male, about 6 months old) were used and divided into six groups, with each group containing three dogs. Groups A and B were placebo-treated for 180 and 240 days, Groups C and D were treated with 10 and 100 mg/kg epristeride for 180 days, and Groups E and F were treated with 10 and 100 mg/kg epristeride for 180 days and then were placebo-treated for 60 days (total 240 days), respectively. Routine analyses were performed at the 1st, 30th, 90th, 180th, and 240th days, and the dogs were autopsied at the 180th or 240th day for systemic examination and measured for relative DNA content in single prostatic epithelial cells. Each prostate was fixed with 4% Formalin, embedded in paraffin, sectioned at 6 micron, and immunohistochemically stained for assaying the relative content (transmittance) of prostatic specific antigen (PSA) and DHT (%) with a microspectrophotometer at 650-nm wavelength. The results were that 180 days of toxicity with epristeride (100 mg/kg) on interstitial cells of testes and DNA in prostatic epithelial cells couldn't reverse during 60 days of convalescence and that the DHT and PSA levels in the gland, the volume of the gland, glandular epithelial cell height, and acinar luminal area could reverse to normal during the same convalescence. To our knowledge this is the first study documenting the toxicity of epristeride. It is necessary to further study the molecular and clinical toxicity of epristeride.