engleski

Aquaporin 9 expression along the male reproductive tract : downregulation by the anti-androgen flutamide

Fluid and solute reabsorption across the epithelium of the male excurrent duct is important for sperm concentration, maturation and storage. Water channels (aquaporins) are known to contribute to transepithelial water movement in many tissues. The present study shows by immunofluorescence and Western blotting that aquaporin 9 (AQP9), which allows permeation of water and various neutral solutes such as urea and polyols, is abundant throughout the male reproductive tract. It is highly expressed in the apical brush border membrane of non-ciliated cells of the efferent ducts and principal cells of rat and human epididymis. AQP9 was not detected in narrow and clear cells, identified by their expression of the vacuolar type H+ATPase. AQP9 was also found all along the vas deferens, in contrast to AQP2 which is detected only in the distal portion, and it was present in epithelial cells of the coagulating gland and dorsolateral prostate. The ventral prostate and seminal vesicle were negative for AQP9. The distribution of AQP9 in rat epididymis was unaffected by colchicine, a microtubule depolymerizing agent, and intracellular staining was weak, suggesting that AQP9 is a constitutively-inserted membrane protein. AQP9 was also present in the epithelium of neonatal rat epididymis as early as one week after birth. In adult rats treated with the anti-androgen flutamide via osmotic minipumps (50 mg/kg body weight/day for 2 weeks), AQP9 staining was significantly decreased in the brush border of epididymal principal cells. Downregulation of AQP9 expression by flutamide was confirmed by Western blotting of epididymal brush border membranes. These data identify AQP9 as a likely candidate for apical transepithelial fluid and/or solute transport in several regions of the male reproductive tract, and indicate that its expression is modulated by androgens in the epididymis.

epididymis; immunocytochemistry; male reproductive organs; sex hormones; vas deferens; water channels

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