Fluoride increases net45Ca uptake by SaOS-2 cells: The effect is phosphate dependent

Autor: Sandra Herring, Michael A. Tanner, John R. Farley, Susan L. Hall
Rok vydání: 1993
Předmět:
Zdroj: Calcified Tissue International. 53:187-192
ISSN: 1432-0827
0171-967X
DOI: 10.1007/bf01321836
Popis: Previousin vitro studies have shown that the effect of fluoride to increase avian osteoblast-like cell proliferation was dependent on the phosphate concentration.In vitro studies have further revealed that fluoride could also have direct effects on osteoblast-like cells to increase phosphate uptake and transiently increase cytosolic calcium. The current studies were intended to determine whether fluoride could increase net45Ca uptake by human osteosarcoma (SaOS-2) cells and, if so, whether those effects would also be phosphate dependent. The results of these studies indicate that fluoride increased net45Ca uptake by SaOS-2 cells, with biphasic dose and time dependencies. After 30 minutes of exposure, net45Ca uptake was increased to a greater extent by 50 μM fluoride (217 ± 16% of control,P < 0.001) than by 200 μM fluoride; and the stimulatory effect of 100 μM fluoride on net45Ca uptake was greater after 20 minutes (187 ±22% of control,P < 0.001) than after 60 minutes (122 ± 7% of control,P < 0.05). These effects of fluoride to increase net45Ca uptake were dependent on the phosphate concentration in the medium. Fluoride had no effect on net45Ca uptake in medium containing 0.4 mM phosphate, but increased net45Ca uptake in medium containing 1.2 or 2.0 mM phosphate (P < 0.005). As the phosphate concentration was increased, the biphasic fluoride dose-response curve was shifted to a lower range of fluoride concentrations. These effects of fluoride were not unique to SaOS-2 cells with very high steady-state levels of skeletal alkaline phosphatase; similar effects were seen in a subpopulation of SaOS-2 cells with much lower alkaline phosphatase levels. Further studies indicated that the effects of fluoride to increase SaOS-2 cell proliferation and skeletal alkaline phosphatase activity showed a similar pattern of phosphate dependency. As the fluoride-dependent increases in3[H]-thymidine incorporation and net45Ca uptake were blocked by verapamil, these data are consistent with the general hypothesis that the osteogenic effects of fluoride are associated with acute effects to increase net Ca uptake.
Databáze: OpenAIRE
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