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Regulation of alkaline phosphatase by 1,25‐dihydroxyvitamin D 3 and ascorbic acid in bone‐derived cells
Author(s) -
Franceschi Renny T.,
Young Jock
Publication year - 1990
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.5650051111
Subject(s) - alkaline phosphatase , hydroxyproline , ascorbic acid , medicine , endocrinology , chemistry , stimulation , biochemistry , enzyme , biology , food science
The bone, liver, and kidney isozyme of alkaline phosphatase (ALP) has been measured in MG‐63 human osteosarcoma cells after treatment with ascorbic acid (AA) and/or 1,25‐dihydroxyvitamin D 3 [1,25‐(OH) 2 D 3 ]. Both compounds were required to achieve maximum ALP activity. When grown in the absence of 1,25‐(OH) 2 D 3 cells had low basal ALP activity regardless of whether media contained AA. In AA‐free medium, 1,25‐(OH) 2 D 3 (10 nM) increased ALP activity fourfold. Addition of AA further increased levels of ALP activity induced by 1,25‐(OH) 2 D 3 to 10–15 times those found in ‐AA controls. The earliest effects of 1,25‐(OH) 2 D 3 were seen after 24–48 h, and ALP activity continued to increase for 6–8 days. AA and 1,25‐(OH) 2 D 3 had similar effects on ALP activity in ROS 17/2.8 rat osteosarcoma cells. In MG‐63 cells the effects of AA and 1,25‐(OH) 2 D 3 could not be simply explained by the ability of these compounds to inhibit cell growth because another mitotic inhibitor, hydroxyurea, had a minimal effect on ALP activity. 1,25‐(OH) 2 D 3 ‐specific induction of ALP ± AA was totally blocked by inhibitors of protein and RNA synthesis. Maximal ALP induction was obtained when cells were plated at low density. Consistent with our previous report (Franceschi et al. 1988 J Biol Chem 263 :18938–18945), 1,25‐(OH) 2 D 3 rapidly stimulated type 1 collagen synthesis and acid‐precipitable hydroxyproline production in MG‐63 cells and this stimulation was further increased by AA. These results suggest that induction of the osteoblast marker, ALP, is directly or indirectly coupled to collagen matrix synthesis and/or accumulation.