Segmental and cellular expression of aquaporins in the male excurrent duct.

The male reproductive tract and accessory glands comprise a complex but interrelated system of tissues that are composed of many distinct cell types, all of which contribute to the ability of spermatozoa to carry out their ultimate function of fertilizing an oocyte. Spermatozoa undergo their final steps of maturation as they pass through the male excurrent duct, which includes efferent ducts, the epididymis and the vas deferens. The composition of the luminal environment in these organs is tightly regulated. Major fluid reabsorption occurs in efferent ducts and in the epididymis, and leads to a significant increase in sperm concentration. In the distal epididymis and vas deferens, fluid secretion controls the final fluidity of the luminal content. Therefore, the process of water movement in the excurrent duct is a crucial step for the establishment of male fertility. Aquaporins contribute to transepithelial water transport in many tissues, including the kidney, the brain, the eye and the respiratory tract. The present article reviews our current knowledge regarding the distribution and function of aquaporins in the male excurrent duct.