PARENT SESSION
Epididymis and Sperm Maturation
302
HORMONAL REGULATION OF AQUAPORIN 9 EXPRESSION IN THE RAT EPIDIDYMIS DURING POSTNATAL DEVELOPMENT.
Pastor-Soler, Nuria1, Fisher, Jane 2, Sharpe, Richard2, Bagnis, Corinne1, Van Hoek, Alfred3, Brown, Dennis 3, Breton, Sylvie 3, 1 2 3
ABSTRACT- Fluid and solute transport across the epithelium of the male excurrent duct is important for proper sperm maturation, storage, and concentration. We have previously shown that the water channel, aquaporin 9 (AQP9), which allows permeation of water and neutral solutes, is abundant throughout the male reproductive tract. In all regions of the epididymis, AQP9 is expressed at high levels in the apical membrane of principal cells, where it appears to be a constitutively-inserted membrane protein. AQP9 was detectable in the epididymis as early as one week after birth. This study examined the hormonal regulation of AQP9 expression during post-natal development. Newborn male rats were divided into groups of 3-8 animals. Each group was exposed during post-natal days 2-12 to different hormonal treatments by subcutaneous injections of: 1) a Gonadotropin releasing hormone antagonist (GnRHa; Antarelix); 2) diethylstilbestrol (DES); 3) ethinyl estradiol (EE); 4) DES plus testosterone (DES+TES); and 5) the anti-androgen flutamide. Control groups received injections with vehicle alone. AQP9 expression was determined 25 days after birth by immunofluorescence and Western blotting, using an affinity purified antibody against the C-terminal tail of AQP9. Quantification of the mean pixel intensity of AQP9-associated fluorescence in the brush border membrane of principal cells from the cauda epididymidis showed a significant decrease in the GnRHa-, DES-, EE- and flutamide-treated groups, compared to control. Rats treated with DES+TES showed a level of AQP9-associated fluorescence comparable to that of the control group. These results were confirmed by Western blotting. Our data show that expression of AQP9 in the developing rat epididymis is down-regulated by anti-androgens. Whether the reduction of AQP9 expression induced by DES and EE is a direct result of steroid receptor-mediated regulation of the protein or is an indirect regulation via changes in the androgen response remain to be determined.
KEY WORDS: aquaporin 9, epididymis, hormonal regulation, post-natal development