Figure 2. Initial segment (a, b), proximal cauda (c), corpus (d, e), and middle cauda (f) epididymidis of a 3-day efferent duct–ligated rat (a), the negative control of a normal adult animal (b), a 21-day orchidectomized rat (c), a 7-day efferent duct–ligated rat (d), a 14-day orchidectomized rat (e), and a 14-day orchidectomized rat supplemented with testosterone (f). (a, c–f) Tissues were immunostained with an anti–cystic fibrosis transmembrane conductance regulator (CFTR) antibody and (b) tissue treated without a primary antibody. In (b), no reaction appears over the epithelium (E) or intertubular space (IT). While a weak diffuse reaction is noted over the apical cytoplasm of the principal cells in (a), as also noted for control animals, only an intense vesicular reaction product (circles) is prominent and uniformly distributed over the apical and supranuclear regions of the principal cells of the corpus and cauda epididymidis (c–e), suggesting the presence of numerous small CFTR-reactive vesicular structures after the differentexperimental treatments. The clear cells (C) maintain weak-to-moderate staining of their apical plasma membrane (open arrows) (f), as do the peritubular myoid cells (curved arrows). No reaction is evident over sperm (S) in the lumen (Lu) or microvilli of the principal cells (c–f). n indicates nuclei of the principal cells. (a, b): 320x; (c–e): 512x.