Vitamin-D-dependent calcium-binding protein (CaBP-9K) in rat growth cartilage.
The presence of vitamin-D-dependent calcium-binding protein (CaBP-9K) in tibial growth-plate cartilage was immunohistochemically demonstrated using a specific antibody to rat duodenal CaBP-9K. The protein was found to be mainly localized in the cytoplasm of maturing chondrocytes. In hypertrophic chondrocytes, CaBP-9K concentrations decreased, and the protein was found in the cytoplasmic processes. No CaBP-specific immunoreactivity was seen in the hypertrophic chondrocytes of the lower calcified hypertrophic zone; in contrast, the protein was found in the extracellular lateral edges of longitudinal septa, i.e. where matrix vesicles are preferentially localized and where cartilage mineralization is initiated. These findings suggest that vitamin D has a direct function in this tissue. It also seems likely that CaBP-9K is an indicator of chondrocyte maturation, and that it is involved in the matrix vesicle-associated process of cartilage calcification.
D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002358:Cartilage, Articular / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D005404:Fixatives; D005455:Fluorescent Antibody Technique; D006651:Histocytochemistry; D007124:Immunoenzyme Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013048:Specimen Handling
D002135:Calcium-Binding Proteins; D005404:Fixatives; D064030:S100 Calcium Binding Protein G