Effect of excessive exposure to sodium fluoride on composition and crystallinity of equine bone tumors.

Sodium fluoride (5 mg/kg of body weight) was fed for 20 months to horses with hereditary multiple exostoses (HME), a skeletal disorder that primarily affects endochondral bones during skeletal development. Rib biopsies were performed on both HME horses not fed fluoride (control) and HME horses that were fed fluoride to obtain comparable specimens for chemical analyses and x-ray diffraction. Fluoride content of the rib from a horse fed fluoride for 20 months was approximately 20 to 30 times higher than that from a control horse. Fluoride content of the bone tumors was higher than those of normal bones in both control and fluoride-fed horses. The effect of fluoride uptake on the Ca/P ratio was slight. The Ca/P ratios did not differ significantly between tumorous and normal ribs. X-ray diffraction studies showed that the crystallinity (ie, crystal size/perfection) of the mineral apatite in tumor of the rib from the control horse was lower than that of normal bone from the same rib. Fluoride, however, induced a marked change in the crystallinity at both the tumorous and the normal bone sites. The crystallinity of the tumor apatite in the fluoride-fed horse exceeded that of normal bone in the control horse. Otherwise, there were not demonstrable fluoride-induced gross or radiographic changes in the bone tumors.