[Effects of antiandrogen TZP-4238 on the prostatic androgen receptor and prostatic androgen in rat]

Pharmacokinetics and biliary excretion of osaterone acetate, a new steroidal antiandrogen, in dogs

The pharmacokinetics and biliary excretion of osaterone acetate (17alpha-acetoxy-6-chloro-2-oxa-4,6-pregnadiene-3,20-dione; OA), a new steroidal antiandrogen, were investigated in intact dogs and biliary fistula dogs after bolus intravenous administration of (14)C-labeled drug. In intact dogs, OA exhibited a biexponential disposition with a very long half-life of 197.9 +/- 109.9 h. OA accounted for almost all the plasma radioactivity. The major route of excretion was in feces via the bile. One-third of the radioactivity in the bile was due to OA. The major biliary metabolite was identified as a glucuronide of 17alpha-acetoxy-6-chloro-21-hydroxy-2-oxa-4,6-pregnadiene-3,20-dione. A significant amount of biliary recycling occurs in dogs.

Expression and degradation of rat androgen receptor following castration, testosterone replacement and antiandrogens administration: analysis by Western blot and immunohistochemistry

To elucidate the autoregulation of androgen receptor (AR) by androgen and antiandrogen, Western blot analysis and immunohistochemical study were performed. Castration reduced the immunodetected AR content, and nuclear staining was lost without cytoplasmic staining. Testosterone (T) supplement restored AR content. Quick response of AR content restoring following single administration of T was observed 48 hours after castration. The recovery of AR content detected by Western blot under each condition was accompanied by recovery of the reduced unclear staining intensities in the epithelia. Neither steroidal nor non-steroidal antiandrogens, chlormadinone acetate and flutamide, altered the AR content in normal rat ventral prostate 5, 12, 24 or 48 hours after single administration. Furthermore, neither of the drugs at various doses altered AR levels 12 hours after single administration. In summary, the rat AR is upregulated by androgen. Single administration of antiandrogens have no effect on immunodetected AR content.

Effects of a new steroidal antiandrogen, TZP-4238 (17 alpha-acetoxy-6-chloro-2-oxa-4, 6-pregnadiene-3, 20-dione), on spontaneously developed canine benign prostatic hyperplasia

The effects of the new steroidal antiandrogen, TZP-4238 on spontaneously-developed canine prostatic hyperplasia (BPH) were studied in comparison with those of chlormadinone acetate (CMA), a steroidal antiandrogen used for the treatment of BPH and prostatic cancer in Japan. Aged beagle dogs (5-9 years old) with spontaneously developed BPH (mean prostate volume, 17.7ml) were treated orally with a placebo, TZP-4238 (0.1 mg/kg/day, 0.01 mg/kg/day), or CMA (3 mg/kg/day), for 25 weeks. Prostate volume was measured by transrectal ultrasonography before treatment and every 5 weeks during treatment. TZP-4238 produced a regression in spontaneously developed canine BPH, its effects being more potent than those of CMA. TZP-4238 reduced the content of testosterone, dihydrotestosterone (DHT) and androgen receptor in the prostates of these animals, suggesting antiandrogenic mechanisms of the agent. TZP-4238 also appeared to reduce 5 alpha-reductase activity by prevention of the androgen action in prostate as described above.