The Efferent Ductules: Structure and Functions

Abstract

There have been three major reviews dealing with structure and function of the efferent ductules (Hamilton, 1975; Robaire and Hermo, 1988; Ilio and Hess, 1994). The first two reviews included efferent ductules along with other regions of the epididymis (Hamilton, 1975; Robaire and Hermo, 1988), due to the lack of sufficient information to warrant a separate chapter. Robaire and Hermo (1988) focused on efferent ductules of the rat and gave detailed morphology of the two epithelial cell types, ciliated and nonciliated. They also provided initial discussions of the major function associated with these ductules, namely fluid reabsorption. In 1994, Ilio and Hess, carried these discussions further by including numerous species and showing, for the first time, morphology of efferent ductules in the dog. Also, from 1988 to 1994, a large number of publications focused on the ultrastructure of these ductules in several species. From 1994 to 2000, there has been a greater focus on the correlation of structure and function, including the major discovery that sulfated glycoprotein-2 (SGP-2), a major secretory protein of Sertoli cells, is synthesized in the same nonciliated cell that is taking up SGP-2 by endocytosis from the ductule lumen (Igdoura et al, 1994; Hermo et al, 1995). A better understanding of efferent ductule physiology has also been uncovered using microcannulation techniques (Clulow et al, 1998). Finally, during this recent period, it was discovered that estrogens play a major role in the regulation of efferent ductule function, and that estrogen receptors are expressed in this region of the male tract to an extent that exceeds even the female reproductive tract (Hess et al, 1997a; Hess et al, 1997b). Based on these recent studies, there is strong evidence that the efferent ductules are essential for male fertility.