Structure and Function of the Ductuli Efferentes - University of Illinois ...

DUCTULI EFFERENTES453Fig. 26. Effects of efferent ductal ligation on Na +, K + -ATPase without ligation. Enzyme activity was measured as reported by Ilio activity in theductuli efferentes and epididymis of the Sprague-Daw- and Hess (1992) for microdissected efferent ductules. Number of anley rat. The ductuliefferentes were ligated at their rete testis origins imals: three to five per group. Significant differences between treatwithout disturbing thesurrounding vasculature and 5 days prior to ment effects are indicated by * within a ductal region (P < 0.05).determining enzyme activity. Shams were treated surgically buteral excurrent ductal epithelium to support intermediarymetabolism, synthesize and metabolize steroids, andsynthesize and metabolize other compounds. References aremade to specific contributions by the efferent ductalepithelium. Finally, the function of phagocytosis of spermhas also been discussed, particularly in epitheliumperturbed with reproductive toxicants.A Conduit for SpermatozoaThe time interval which spermatozoa require to passalong the length of the ductuli efferentes has beendetermined to be 45 min in the rat (English and Dym,1982), but little is known for other species. As discussed inthe previous sections, it is believed that the main forcesthat propel spermatozoa along the ductuli efferentes are themotility of cilia and the contraction of smooth muscle cellssurrounding the epithelium (Lucas, 1932). Evidence for thisfunction is the observation that the smooth muscle layercontracts in vivo (MacMillan and Harrison, 1955; Risley,1958) and that tracers injected into the ductuli lumen aretransported even when the fluid flow from the testis isprevented by a ligature (MacMillan and Harrison, 1955;MacMillan and Aukland, 1960).There appears, however, to be some controversysurrounding this simplistic mechanism of sperm transport.Talo (1981) has observed that although ciliary beat moveddirections. In fact, the cilia have been postulated to reducethe flow of fluids by creating a reflux (Winet, 1980). Hess(unpublished observation using video microscopy ofmicrodissected ductules) has observed ciliary beat thatappeared to serve a function of simply stirring the fluid,possibly for homogeneous reabsorption of fluids. Also,although contractions appeared to spread from the terminalductule toward the caput epididymis, moving the luminalcontents forward, sperm clumps in preterminal ductuleswere observed to move back and forth but with negligiblenet movement (Talo, 1981).In addition, other factors have been proposed to influencefluid flow and sperm transport along the ductules: 1)constant secretion of fluid by the seminiferous epithelium(Mason and Shaver, 1952); 2) contraction of themyoepithelial layer of the seminiferous tubule and tunicaalbuginea of the testis (Hargrove et al., 1977); 3) thevacuum created by the ejaculation of sperm from the lowertract and by the absorption of fluid (Mason and Shaver,1952); and 4) increased pressure due to the pattern ofbranching and convergence of ductuli (MacMillan, 1953;Talo, 1981).In the first two instances, during the contraction of themyoepithelial layer and tunica albuginea in the testis, apressure gradient was created in the excurrent duct, the