FLUORIDE SELECTIVELY STIMULATES NA-DEPENDENT PHOSPHATE-TRANSPORT IN OSTEOBLAST-LIKE CELLS

The influence of fluoride (F) on the transport of P(i) was investigated in the osteoblast-like cell line UMR-106. Exposure of cells to F induced a dose-related stimulation of the Na-coupled P(i) transport. P(i) transport was significantly increased 6 h after 1 mM F incubation, with maximal response observed at 24 h (F 38.0 +/- 2.3, vehicle 19.8 +/- 1.2 pmol.mu-g DNA-1.4 min-1; P < 0.001). Na-dependent alanine transport was not changed by F. The selective effect of F on P(i) transport was not associated with changes in adenosine 3',5'-cyclic monophosphate, cell proliferation, or alkaline phosphatase activity. However, it was completely blunted by inhibiting translational processes with cycloheximide. Furthermore, F enhanced the stimulatory effect on P(i) transport of various mitogens such as fetal calf serum, insulin, and insulin-like growth factor I. In conclusion, F can selectively enhanced the activity of the P(i) transport system present in the plasma membrane of UMR-106 osteoblast-like cells by a mechanism that probably involves newly synthetized proteins.