**3. Discussion**

To the best of our knowledge, this is the first study to evaluate the inhibitory effect of AST on BPH in vivo. BPH is characterized by an enlarged prostate. Castration was performed to eliminate the influence of endogenous androgen, and rats were given a 5 mg/kg BW/day dose of exogenous androgen to build the BPH model, considered to be relatively closer to the pathogenesis of clinical BPH, as previously reported [17,18]. In the present study, except for the sham-operated rats, BPH model rats were randomly divided into five groups: BPH model control rats, AST (20 mg/kg, 40 mg/kg, and 80 mg/kg)- treated BPH model control rats, and EPR-treated BPH model control rats. A decline in the prostate and ventral prostate weights and index of prostates and ventral prostates in the AST-treated groups were observed, and a significant decline was found in the 80 mg/kg AST-treated group as compared with the BPH model control rats. The prostate and ventral prostate weights and the prostate index values of prostates and ventral prostates in the 80 mg/kg AST-treated rats were also lower than those in the EPR-treated rats. However, the dorsal prostate weights and dorsal prostate index values of the AST-treated rats did not differ significantly from those of the BPH model control rats. Hence, the results sugges<sup>t</sup> that AST might have a more significant inhibitory effect on ventral prostates than dorsal prostates in T-induced rats.

Histological observation of BPH is described as the proliferation of the stroma and epithelia. After treatment for four weeks, the histomorphology of prostates in the T-induced BPH rats was evaluated. The proliferation characteristics of epithelia such as tall columnar epithelia, simple multifocal epithelial thickening with cellular crowding, and folding of the lining epithelia extending into the lumina were markedly observed in the BPH model control group, which were gradually alleviated following AST treatment. The epithelial thicknesses of prostates in all rats were measured, and secretory granules in the epithelia were also observed under TEM. The epithelial thickness of prostates in the AST-treated rats was markedly lower than that in the BPH model control rats. It was also reported that the secretory granules that release their contents into the gland lumen increased in the T-induced BPH model as compared with the normal control [19,20]. In the present study, fewer secretory granules in the epithelia were observed in the AST-treated rats than in the BPH model control rats. These results indicate that AST might ameliorate the epithelial thicknesses of prostates and decrease the number of secretory granules in epithelia in T-induced BPH rats.

T and DHT are the principal androgens in the prostate, possibly related to the development of BPH [21]. The levels of T and DHT of prostates in the three AST-treated groups decreased as compared with the BPH model control group; a significant decline was found in the T level of prostates in the 40 mg/kg and 80 mg/kg AST-treated rats and

the DHT level of prostates in the 40 mg/kg AST-treated rats, albeit not in a dose-response relationship. These results indicated that AST might cause the decrease in T and DHT levels in prostate tissues of T-induced BPH rats.

Oxidative stress, defined as the imbalance between the production and elimination of reactive oxygen species, can be alleviated by antioxidants and is one of several parameters considered to play a pivotal role in the development of BPH [22–24]. SOD, a group of antioxidant enzymes, plays an important role in oxidative stress in cells [25]. Research has suggested that erythrocyte SOD activity was significantly decreased in BPH patients as compared with age- and sex-matched healthy subjects [26]. Moreover, T injection in the BPH model has been shown to weaken cellular antioxidant mechanisms, including a decrease in SOD activity [27–29]. In this study, the SOD activity of prostates in the ASTtreated rats increased, while the SOD activity of prostates in the 40 mg/kg and 80 mg/kg AST-treated rats was significantly higher than that in the BPH model control rats. These results demonstrated that AST might inhibit T-induced BPH in rats by regulating SOD activity. Further experiments on the mechanism by which AST regulates SOD activity in the present study will be carried out.

#### **4. Materials and Methods**
