Bone Responses of Rachitic Rats to High Fluoride

Studies of a high fluoride diet were undertaken in vitamin D-deficient rats to determine the effects on metabolically abnormal bone structure and mineralization. Young Holtzman rats were divided into 3 groups: Rachitic-Fluoride, Rachitic-Control, Normal-Control. The Rachitic-Fluoride group placed on a rachitic diet was given distilled water to which 120 ppm fluoride as NaF was added. The Rachitic-Control group was placed on a rachitic diet and given distilled water. Animals in the Normal-Control group were given a normal diet and distilled water. After 4 weeks femoral diaphyses and distal metaphyses were removed. Acid and alkaline phosphatase were studied on frozen sections. Decalcified paraffin sections were stained with H&E, PAS and toluidine blue. Fresh, mineralized hand-ground sections were stained using the Villanueva tetrachrome method. Parathyroids and kidneys were removed and paraffin sections stained with H&E and PAS. Serum Ca was measured by a titration method. The following observations were made in high fluoride-treated rachitic rats: (1) well-being of the rats was not appreciably affected by 120 ppm fluoride in water; (2) serum Ca was maintained at normal levels; (3) no histological changes were evident in the kidneys; (4) morphological changes occurred in the parathyroid gland cells; (5) both phosphatase enzyme activities were increased over Normal-Controls, but were similar to Rachitic-Controls; (6) increase in epiphyseal plate width occurred; (7) there were no diagnostic abnormalities of new lamellar bone formation in routine demineralized stained sections; (8) tetrachrome stained sections revealed that new bone mineralization occurred but contained a low mineral content per unit volume of bone. Since these observations were compared with both Rachitic and Normal Controls, they are solely due to fluoride.