Expression and regulation of H+K+ATPase in lysosomes of epithelial cells of the adult rat epididymis

Endocytosis is an important event in the epididymis as it contributes to a luminal environment conducive for sperm maturation. Principal and clear cel ls contain numerous lysosomes which degrade many substances internalized by endocytosis from the epididymal lumen. The interior of the lysosomes depen ds on low pH to activate the release of their enzymes and to activate their acid hydrolases. In the present study, H+K+ATPase was localized by light m icroscopy in the adult rat epididymis of intact and of orchidectomized anim als supplemented with testosterone or not. In normal animals, numerous lyso somes of nonciliated cells of the efferent ducts were intensely reactive fo r anti-H+K+ATPase antibody. In the initial segment, only a few lysosomes of principal cells were reactive. In the intermediate zone of the epididymis, numerous lysosomes of principal cells were intensely reactive, while the n umber of intensely reactive lysosomes decreased progressively from the prox imal caput to the distal caput with none being seen in the proximal corpus region. In the distal corpus and cauda regions, only a few lysosomes of som e principal cells were reactive. In contrast, clear cells of all regions sh owed intense reactivity. Orchidectomy resulted in the abolishion of H+K+ATP ase in lysosomes of principal cells of all regions except the initial segme nt. However, while clear cells of the caput and corpus regions also became unreactive, those of the cauda region remained as reactive as in controls. Orchidectomized animals supplemented with testosterone maintained a stainin g pattern similar to controls for both cell types. These observations demon strate the presence in principal and clear cells of H+K+ATPase which may ha ve an important role in acidifying the interior of their lysosomes. However , there is a region-specific expression of H+K+ATPase in lysosomes of princ ipal cells, unlike that for clear cells. In addition, H+K+ATPase expression in lysosomes of principal cells depends on testosterone in all regions exc ept the initial segment. However, in the case of clear cells, only those of the caput and the corpus regions are dependent on testosterone, while thos e of the cauda region appear to be regulated by some other factor. (C) 2001 Wiley-Liss, Inc.