Expressional Modulation of Aquaporin 1 and 9 in the Rat Epididymis by an Anabolic-Androgenic Steroid, Nandrolone Decanoate

The spermatozoa become mature in the epididymis which is divided into initial segment and caput, corpus, and cauda epididymis. The water movement across the epididymal epithelium is important for creating luminal microenvironment for sperm maturation. Aquaporins (Aqps) are water channel proteins, and expression of Aqps is regulated by androgens. The current research was focused to examine expressional regulation of Aqp1 and Aqp9 by an androgenic-anabolic steroid, nandrolone decanoate (ND). The ND at the low dose (2 mg/kg body weight/week) or high dose (10 mg) was subcutaneously administrated into male rats for 2 or 12 weeks. Transcript levels of Aqp1 and Aqp9 were determined by quantitative real-time polymerase chain reaction (PCR) analyses. In the initial segment, level of Aqp1 was decreased with 12 week-treatment, while Aqp9 level was decreased by the high dose treatment for 12 weeks. In the caput epididymis, Aqp9 expression was decreased by the low dose treatment. The 2 week-treatment resulted in an increase of Aqp1 level but a decrease of Aqp9 expression in the corpus epididymis. In the corpus epididymis, the 12 week-treatment at the low dose caused the reduction of Aqp1 and Aqp9 levels, but the high dose treatment resulted in an increase of Aqp1 expression and a decrease of Aqp9 level. In the cauda epididymis, Aqp1 expression was decreased by 2 and 12 week-treatments, while increases of Aqp9 levels was detected with the high dose treatment for 2 weeks and with 12 week-treatment. These findings indicate differential regulation of Aqp1 and Aqp9 expression among epididymal segments by ND.