Androgens upregulate aquaporin 9 expression in the prostate

Objectives: Aquaporins (AQP) function as selective pores allowing water, glycerol and other small solutes to pass through the cell membrane. We previously reported that AQP are expressed in the prostates of both humans and rats. The present study investigated the androgen‐dependent expression of AQP9 in the prostate in vivo and in vitro. Methods: Rat ventral prostate tissue specimens and a normal human prostatic epithelial cell line (PNT2) were used. AQP9 messenger ribonucleic acid (mRNA) and protein expression were examined using real‐time polymerase chain reaction, Western blotting and immunohistochemical methods. Androgen modulation was achieved by surgical castration, treatment with testosterone propionate (5 µg/g bodyweight) or bicalutamide (20 µg/g bodyweight), and the ribonucleic acid interference (RNAi) method of the androgen receptor (AR). The synthetic small interfering RNA was transfected into PNT2 at a concentration of 10 nM, and the RNAi effect was evaluated using a Western blotting analysis. Results: AQP9 mRNA and protein were expressed in the rat prostate. Surgical castration or bicalutamide treatment significantly decreased their expression. In addition, the treatment with testosterone propionate after castration restored the expression to the level of the controls. An RNAi experiment in PNT2 also decreased the expression. Conclusions: AQP9 expression in the prostate is controlled by androgens.