ALP induction by β-glycerophosphate during the non-mineralization phaseIn Vitro

Abstract

β-GP influences on rat osteoblast development at the early period of culture i. e., the non-mineralization phase, and changes with the different cell passages were investigated. Alkaline phosphatase (ALP) was chosen as a main object. Northern blot analysis revealed up to two-fold increase in the steady state level of ALP mRNA after stimulation of rat osteoblast with 10 mM β-GP. Likewise, 10 mM β-GP induced a 10–30 % increase in ALP activity (P< 0. 01) of early passages (1 to 4), but not of later passages (5 to 6). The β-GP induced increase in ALP activity was totally inhibited by the protein synthesis inhibitor, cycloheximide (50 μM). β-GP stimulation was found to be without effect on cell proliferation measured as³H-thymidine incorporation. It is concluded that β-GP has no effect on proliferation but induces an increase in both mRNA level and activity of ALP in the non-mineralization phase of cultures of fetal rat calvarial cells, which lasts for several passages but will disappear in older cultures.

Keywords

fetal rat calvarial cells / β-glycerophosphate / alkaline phosphatase activity / mineralization

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