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Role of β‐GP‐derived pi in mineralization via ecto‐alkaline phosphatase in cultured fetal calvaria cells
Author(s) -
Anagnostou Fani,
Plas Christiane,
Nefussi JeanRaphaël,
Forest Nadine
Publication year - 1996
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(199608)62:2<262::aid-jcb14>3.0.co;2-n
Subject(s) - alkaline phosphatase , levamisole , calvaria , cell culture , beta (programming language) , pi , chemistry , enzyme , biochemistry , microbiology and biotechnology , medicine , endocrinology , biology , in vitro , immunology , genetics , computer science , programming language
The permissive effect of β‐GP on mineralization in cultured rat fetal calvaria cells was investigated in relationship with phosphohydrolase activity of ecto‐ALP at physiological pH range. β‐GP present in the culture medium for 8 days exerted a stimulatory effect on 45 Ca incorporation into matrix cell layers while the ecto‐ALP activity level measured on intact cells with a saturating concentration of p cells grown either in the presence or absence of β‐GP. In both types of cultures, β‐GP addition inhibited p NPP hydrolysis in a competitive and reversible manner and increased Pi concentration in the medium. The dose dependency of the effect of β‐GP on 45 Ca incorporation and generation of Pi was similar (kϕ = 3 mM). Levamisole, but not dexamisole, inhibited both p NPP and β‐GP hydrolyses, which were likely catalyzed by the same ecto‐enzyme. The rate of 45 Ca incorporation into matrix cell layers, which was high (0.90 μmol/4h/mg cell protein) in cells grown in the absence of β‐GP, was inhibited by 50% by levamisole. In cells grown in the absence of β‐GP, the 45 Ca incorporation rate increased progressively after β‐GP addition, reaching after 12 h the value of cultures grown in the presence of β‐GP, the increase being totally inhibited by levamisole. In both types of cells, addition of exogenous Pi at concentrations corresponding to medium levels of β‐GP‐derived Pi rapidly led to high 45 Ca incorporation rate which was unaffected by levamisole. β‐GP removal from cultures grown in its presence reduced by 50% the 45 Ca incorporation rate which recovered the initial value after exogenous Pi addition independently of levamisole presence. Thus, mineral deposition did not affect the level and catalytic efficiency of ecto‐ALP to hydrolyze β‐GP in cultured fetal calvaria cells, yet it influenced the β‐GP‐stimulatory effect on mineralization so as to render this process not sensitive to high medium Pi levels. © 1996 Wiley‐Liss, Inc.