title: Immunoreactive calbindin-D9K in bone matrix vesicle.
abstract: This electron microscope study describes the subcellular occurrence and distribution of immunoreactive calbindin-D9K in the trabecular metaphyseal and compact cortical bone of normal rats, rachitic vitamin-D-deficient rats, and rachitic rats given 1,25-(OH)2D3. Undecalcified bones were embedded in Lowicryl K4M and calbindin-D9K antigenicity was detected by the protein A-gold method. Immunoreactive calbindin-D9K was localized in the cytoplasm and cell processes of osteoblasts and osteocytes. Immunoreactive calbindin-D9K was also found within matrix vesicles and calcifying matrix vesicles, where it lay over the needle-shaped crystallites, at the apparent site of initial crystal formation, but not along the whole crystallites. In fully mineralized bone it occurred at the same site, over the crystallites. Calibindin-D9K was vitamin-D-dependent in the osteoblasts and matrix vesicles, where its presence was correlated with the reappearance of crystallites in 1,25-(OH)2D3-treated vitamin-D-deficient rats. This suggests that immunoreactive calbindin-D9K is involved in mineral deposition in bone matrix vesicles. Abnormal intracellular calcification associated with calbindin-D9K antigenicity in the osteoblasts of 1,25-(OH)2D3-treated vitamin-D-deficient rats indicates that immunoreactive calbindin-D9K may also play a part in abnormal intracellular mineral deposition.
authors.affiliation: INSERM-U.120, alliée CNRS-SDI I19261, Hôpital Robert Debré, Paris, France.
authors.forename: N
authors.initials: N
authors.lastname: Balmain
authors.forename: D
authors.initials: D
authors.lastname: Hotton
authors.forename: P
authors.initials: P
authors.lastname: Cuisinier-Gleizes
authors.forename: H
authors.initials: H
authors.lastname: Mathieu
mesh_terms: D000818:Animals; D001857:Bone Matrix / Q000737:chemistry* / Q000648:ultrastructure; D064026:Calbindins; D002117:Calcitriol / Q000627:therapeutic use; D003593:Cytoplasm / Q000737:chemistry; D005109:Extracellular Matrix / Q000737:chemistry; D005260:Female; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D015388:Organelles / Q000737:chemistry; D010006:Osteoblasts / Q000737:chemistry* / Q000648:ultrastructure; D010011:Osteocytes / Q000737:chemistry* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D014808:Vitamin D Deficiency / Q000188:drug therapy / Q000378:metabolism
chemical_list: D064026:Calbindins; D064030:S100 Calcium Binding Protein G; C576508:S100g protein, rat; D002117:Calcitriol