Deposition and retention of fluoride and radiocalcium in the growing rat

¹ National Institute of Dental Research and National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland

Radiocalcium and fluoride were administered daily for 30 days to young rats. At 30 and 60 days, the tibia, femur, mandible, teeth and remaining skeleton were analyzed for Ca⁴⁵ and F. The tibia was divided into several segments including the proximal epiphysis, the original diaphyseal segment, and those portions of the diaphysis added from 0 to 30 days and 30 to 60 days. Fluoride had no effect on the Ca⁴⁵ or ash of bone but reduced Ca⁴⁵ uptake by molar enamel. Ratios of F to Ca⁴⁵ were dissimilar in the various tibial segments. Between 30 and 60 days essentially no Ca⁴⁵ or F was lost from the skeleton, tibia or tibial segments excepting the 0–30-day proximal diaphyseal increment. Seventy per cent of the Ca⁴⁵ and forty per cent of the F lost from this segment was found in the adjacent segment formed during the second 30-day period. These results suggest that much of the Ca⁴⁵ and F released during remodeling of the ends of the growing bone did not enter the general circulation, but was deposited in the immediate vicinity.