The effect of sodium fluoride on the rates of synthesis and degradation of bone collagen in tissue culture

The effect of chronic fluoride administration on rat condylar cartilage

Morphometrical and histochemical techniques were used to demonstrate changes to the cartilage layer of the rat temporomandibular joint condyle following chronic exposure to fluoride. An increase in thickness of the cartilage layer was noted in rats given 100 parts per million sodium fluoride in drinking water. No significant changes were observed with either control or low dose (10 parts per million) groups. The observed thickening was attributable to an increase in number and size of cells of the lower hypertrophic zone. Accumulations of glycogen were observed in these cells, which reflects the inhibitory effect of fluoride on glycolysis. Stimulation of chondrocytes by fluoride may have delayed the normal processes of capillary invasion, resulting in thickening of the cartilage layer. No changes to staining patterns of immature or mature types of collagen were observed, nor did the staining pattern of detectable glycosaminoglycans change due to fluoride.

A comparison of some effects of fluoride on apatite formation in vitro and in vivo

In a liquid (22 degrees C) saturated with and in contact with powdered bone apatite, the fluoride ion activity was adjusted to 1-10 parts/10(6). Due to the fluorapatite (FAP) supersaturation produced hereby, a rapid formation of this salt occurred leading to a decrease of the concentration of the ions involved. When no more fluoride was available in the liquid, the concentrations of calcium and phosphate increased again, due to dissolution of presumably hydroxyapatite (HAP). Fifty four rats were given either 10, 20, or 40 mg NaF per kg body weight intraperitoneally. The animals were sacrificed from 5 min to 96 h after the injection. The fluoride concentration in plasma increased to a peak, after which it decreased. Plasma calcium decreased and remained low until the fluoride had attained normal levels. The intensity of mineralization of the growing dental hard tissue was monitored on microradiographs. Corresponding to the plasma fluoride peak and the decrease of plasma calcium, a hypermineralized layer was formed while a hypomineralized zone was formed during plasma calcium increase after disappearance of fluoride. Similarities and dissimilarities between the in vitro and the in vivo experiments are discussed.

Effect of fluoride on collagen synthesis in the rat

Thirty-six young rats were used to determine the effect of the fluoride on collagen synthesis in healing of fracture. Eighteen rats received 100 ppm fluoride per day, the other 18 were not given fluoride and were used as controls. Then the tibiae of the 36 rats were successively fractured and the animals killed. That is, the first 14 animals of either group were killed one a day, and then the remaining four animals were killed on days 21, 28, 35, and 45 as the tibiae were fractured. Collagen synthesis of the callus was examined histochemically and histologically. In the fluoride-treated group, collagen synthesis was found to be defective, while it was normal in the controls.

Fluoride sensitivity of cells from different organs

The fluoride sensitivity of cells released from rat livers and kidneys by collagenase perfusion was investigated by measuring effect on protein synthesis rate in vitro. Both cell types were sensitive to fluoride with clear concentration/effect relationships. Significant difference in sensitivity for fluoride between the cell types was found, with the kidney cells being the most sensitive type.

Effect of fluoride on protein and collagen biosynthesis in rabbit dental pulp in vitro

The time course for incorporation of KC-proline into various fractions of rabbit dental pulp in vitro has been measured. In the TCA-soluble precursor pool a steady state level of activity was indicated upon incubation after 3 h, whereas incorporation into protein and 14C-hydroxyproline, i.e. collagen formation, increased linearly for 9 h, leveling off upon further incubation. A lag period of about 3 h was indicated for the appearance of high molecular weight 14C-activity, including 14C-hydroxyproline, in the medium, increasing linearly from 3 h to the end of the incubation period (22 h). In this system, fluoride exhibited a dose-dependent inhibitory effect. At 5.3 mM fluoride the uptake of 14C-proline into the TCA-soluble pool was inhibited by about 50%, and the incorporation into protein and the subsequent conversion to hydroxyproline by about 90 and 60%, respectively. Release of collagen, i.e. 14C-hydroxyproline-containing material, seemed to be the process most sensitive to fluoride; it was inhibited by about 50% at the lowest concentration (1.3 mM) tested.

The effects of fluoride on the mineralization of embryonic chick tibiae in organ culture

The effects of various concentrations of fluoride on the mineralization of embryonic chich tibiae were studied in vitro. After 4 days incubation in medium with a physiological Ca x PO4 product (1.8 mM2), fluoride promoted a highly significant dose-related enhancement of bone mineralization. In experiments where the medium Ca x PO4 product was varied by changing either Ca or PO4 while keeping the other constant at 1.8 mM, fluoried at 7.5 muM or at 100 muM affected bone mineralization differbntly at low and high products. At medium Ca x PO4 products below 3 mM2, fluoride significantly enhanced bone mineral deposition compared to paired control bones, while at products above 5 mM2, fluoride significantly inhibited bone mineralization. This dual effect of fluoride was observed in both live bones and bones metabolically inhibited by 1 mM iodoacetic acid. Comparison of the effects of fluoride on the mineralization of live and dead bones suggested that the effects are dependent on the cellular control of Ca x PO4 product in the bone extracellular fluid. These findings support the hypothesis that fluoride may play an important role in governing the rate of mineralization in growing bones.

Histologic and histometric study of the effect of fluoride on the rat mandibular condyle

The effect of fluoride on the rat mandibular condyle was studied histologically and histometrically. The condyles of the rats that received 50 ppm fluoride in the drinking water for 17 weeks did not differ in structure from those of the control rats fed tap water containing 1 ppm fluoride. However, the condyles of the rats given 100 ppm fluoride in the drinking water for the same period showed a significant increase in both the thickness of the cartilage layer (P smaller than 0.02) and the density of cancellous bone (P smaller than 0.01) when compared to the controls. The thickening of the cartilage layer was due to an increase in the number of hypertrophied chondrocytes. The trabeculae of cancellous bone were thicker and consequently the bone marrow spaces were extremely reduced. The trabeculae contained more calcified cartilage in their cores.