BPH was induced by subcutaneous injection of testosterone propionate (TP, 3 mg/kg, Tokyo Chemical Ins. Co., Tokyo, Japan) for 4 weeks. After 1 week of acclimatization, the rats were divided into five groups: (A) a normal control group that received phosphate-buffered saline (PBS, p.o.) with corn oil (s.c.); (B) a BPH group that received PBS (p.o.) with TP (s.c.); (C) a positive control group that received finasteride (10 mg/kg, p.o.) with TP (s.c.); and (D and E) YJT groups that received YJT at 200 or 400 mg/kg (p.o.), respectively, with TP (s.c.). Finasteride, a 5α-reductase inhibitor, was used as a positive anti-BPH drug and was purchased from Sigma-Aldrich (St Louis, MO, USA). Its effective dose for treating BPH was determined based on a previous study [19 (link)]. All materials were administered to animals once daily for 4 weeks, and body weight was measured weekly. The application volumes were 5 mL/kg for oral administration (PBS, finasteride and YJT) and 3 mL/kg for subcutaneous injection (corn oil and TP) and were calculated in advance based on the most recently recorded body weights of individual animals. After the last treatment, all animals were fasted overnight and euthanized using pentobarbital at 100 mg/kg body weight injected intraperitoneally (Han Lim Pharmaceutical. Co. Ltd., Yongin, Korea). Blood samples were drawn from the caudal vena cava, and the serum was separated by centrifugation. Serum was stored at at −80°C for hormone assays. The prostates were removed immediately and weighed. Relative prostate weight was calculated as the ratio of prostate weight to body weight. The percentage inhibition of the increase in prostate weight induced by YJT was determined according to previous study [20 (link)]. The ventral lobe of the prostate was divided in half. One half was fixed using 10% neutral-buffered formalin and embedded in paraffin for histomorphology and the other was stored at −80°C for other analyses.
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