Coexistence of renin and cathepsin B in secretory granules of granular duct cells in male mouse submandibular gland.
Cathepsin B, a representative lysosomal cysteine proteinase, has been demonstrated to coexist with renin in secretary granules of rat pituitary LH/FSH cells and renal juxtaglomerular cells. We investigated immunocytochemically the localization of cathepsins B, H, and L in the submandibular gland of male mice, in which active renin is also produced. By light microscopy, granular immunodeposits for cathepsin B were detected in epithelial cells of the gland, particularly in granular duct cells and interstitial cells. Immunoreactivity for cathepsins H and L was mainly found in interstitial cells, although that for cathepsin H was weakly seen in acinar cells. By electron microscopy, immunogold particles indicating cathepsin B intensely labeled small granules near the Golgi complex of granular duct cells and weakly labeled large secretory granules, whereas those showing renin labeled both granules. Double immunostaining co-localized immunogold particles showing renin and cathepsin B in small perinuclear granules near the Golgi complex. Some immunopositive granules seemed to be closely associated with the Golgi elements. These results indicate that the co-localization of renin and cathepsin B is also seen in secretory granules of granular duct cells in the mouse submandibular gland, as seen in rat juxtaglomerular and LH/FSH cells. This suggests that cathepsin B is one of the possible candidates for the renin-processing enzyme.
Sano
K
K
Department of Cell Biology and Neuroanatomy, School of Medicine, Iwate Medical University, Japan.
Waguri
S
S
Sato
N
N
Kominami
E
E
Uchiyama
Y
Y
D000818:Animals; D002401:Cathepsin B / Q000032:analysis*; D003594:Cytoplasmic Granules / Q000201:enzymology* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D016253:Microscopy, Immunoelectron; D012083:Renin / Q000032:analysis*; D013363:Submandibular Gland / Q000201:enzymology* / Q000648:ultrastructure
D002401:Cathepsin B; D012083:Renin