Figure 20. Diagrammatic representation of aquaporin-1 (AQP-1) (upper panel) and AQP-9 (middle panel) expression in normal adult animals and AQP-9 expression 14 days after orchidectomy or efferent duct (ED) ligation (lower panel) in the EDs, initial segment (IS), caput (CAP), and cauda (CAU) regions of the epididymis. Upper panel: expression of AQP-1 is noted over the microvilli (Mv) of nonciliated cells (NC) and cilia (arrow) of ciliated cells (C) of the EDs; endothelial cells of vascular channels (VC) of the intertubular space of the EDs and epididymis and myoid cells (My) underlying the ducts of the ED and IS regions. Middle panel: expression of AQP-9 is restricted to the Mv of the NC of the EDs. In the epididymis, principal cells (P) show intense reactivity of their Mv in the IS and CAU regions while only weak to moderate reactivity in the CAP and corpus regions; apical endocytic vesicles of the P of the CAU region also show a reaction for anti—AQP-9 antibody, as do clear cells (C) of the CAU region only. Lower panel: after orchidectomy or ED ligation, no change in expression is noted in the EDs. However, in the epididymis, the P of the IS and C of the CAU region become unreactive, while no change in expression is noted for the P of the CAP, corpus, or CAU regions. The administration of testosterone at high levels to orchidectomized animals does not restore the staining pattern of the P of the IS and C of the CAU region to that observed in normal untreated animals.