2.3. TP Induced Rat BPH Model

BPH in rats was induced following the method described previously [19]. Testosterone propionate (TP; Tokyo Chemical Ins. Co., Tokyo, Japan) dissolved in corn oil (3 mg/kg) was administered daily via subcutaneous injection (S.C.) to the animals, excluding the normal control group, for six weeks. The rats were randomly assigned to six groups as follows (n = 5/group): (a) normal control (NC, corn oil S.C. + phosphate buffered saline (PBS) orally (P.O.)) group; (b) BPH (TP 3 mg/kg/day S.C. + PBS P.O.) group; (c) Fina (positive control; TP 3 mg/kg/day S.C. + Finasteride 10 mg/kg/day P.O.) group; and (d–f) ACE (TP 3 mg/kg/day S.C. + 20 mg, 50 mg, 100 mg/kg/day ACE P.O., respectively) groups. The 5α-reductase 2 inhibitor, finasteride, was obtained from Tokyo Chemical Industry Co., Ltd. The materials mentioned above were orally administered on a daily basis for a duration of six weeks. The rats were weighed every week to determine the dosage. Following the last treatment, the animals underwent a 12 h fasting period before being euthanized, at which point whole blood samples were collected from the cauda vena cava. The entire prostate was promptly excised and weighed, and the prostate index was calculated by determining the ratio of prostate weight (mg) to body weight (100 g).