Short-term effects of fluoride and strontium on bone formation and resorption in the mouse

The early effects of sodium fluoride (0.80 mg/kg/d) and strontium chloride (0.27%) given alone, or in combination in drinking water, on bone metabolism were examined in the mouse using dynamic histomorphometric methods. Four weeks of oral strontium supplementation increased the osteoid surface and reduced the number of acid phosphatase-stained osteoclasts. However the trabecular calcified bone volume was not augmented. By contrast, short-term treatment with fluoride produced a rapid stimulatory effect on bone formation at a dose that did not affect the bone mineralization rate. Four weeks of fluoride supplementation induced a rapid 21.1% increase in the osteoblastic surface and a 26.3% stimulation of the bone matrix apposition rate evaluated by the double tritiated proline labelling method, which resulted in a 29% increase in the amount of osteoid. This rapid stimulation of the bone formation rate without detectable change in osteoclastic bone resorption led to a 12% increase in the trabecular calcified bone density. This study shows that fluoride and strontium produce distinct early effects on bone formation and resorption in the mouse and that fluoride exerts a rapid stimulatory effect on the bone matrix synthesis rate through an augmentation of the number of bone-forming cells.