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The mechanism of β‐glycerophosphate action in mineralizing chick limb‐bud mesenchymal cell cultures
Author(s) -
Boskey Adele L.,
Guidon Peter,
Doty Stephen B.,
Stiner Dalina,
Leboy Phoebe,
Binderman Itzhak
Publication year - 1996
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650111113
Subject(s) - alkaline phosphatase , phosphatase , mineralization (soil science) , biochemistry , chemistry , mesenchymal stem cell , phosphoprotein , phosphorylation , limb bud , microbiology and biotechnology , biology , enzyme , gene , organic chemistry , nitrogen
Differentiating chick limb‐bud mesenchymal cells plated in micromass culture form a cartilage matrix that can be mineralized in the presence of 4 mM inorganic phosphate (P i ) and 1 mM calcium. Previous studies showed that when β‐glycerophosphate (βGP) is used in place of P i , the mineral crystals formed are larger and differ in distribution. The present study shows that the difference in distribution is not associated with alterations in cell proliferation, protein synthesis, or with collagen, proteoglycan core protein, or alkaline phosphatase gene expression. Cultures with 2.5, 5, and 10 mM βGP did show different levels of alkaline phosphatase activity, and in the presence of low (0.3 mM) Ca had different P i contents (4, 6, and 9 mM, respectively), indicating that the increase in CaxP product may in part be responsible for the altered pattern of mineralization. However, cultures with βGP in which alkaline phosphatase activity was inhibited with levamisole still had an altered mineral distribution as revealed by Fourier transform‐infrared (FT‐IR) microspectroscopy. The presence of a casein kinase II‐like activity in the mineralizing cultures, the ability of specific inhibitors of this enzyme to block mineralization, and the known ability of βGP to block phosphoprotein phosphatase activity suggests that altered patterns of matrix protein phosphorylation may influence mineral deposition in these cultures. (J Bone Miner Res 1996;11:1694‐1702)