THE METABOLISM OF FLUORINE IN THE RAT USING F¹⁸ AS A TRACER

¹ Division of Medical Physics and the Crocker Radiation Laboratory of the University of California, Berkeley, Calif.

Radioactive tracer and radioautographic technics using NaF tagged with F¹⁸ were employed to study the metabolism of soluble fluoride ion in rats. Young adult females and mature females were used for these studies. F¹⁸ was administered orally and by intravenous injection in an essentially carrier-free state and with added fluoride carrier. Radioautographs were prepared from the femurs of both young and mature rats. The results permit the following conclusions:

1. Cell membranes appeared to be freely permeable to F¹⁸ when it was administered as NaF.

2. There did not seem to be any significant deposition of F¹⁸ in any of the soft tissues of the rat, with the possible exception of the kidney, when it was given with stable fluoride in amounts ranging from 0.5 µg to 10 mg. per kilogram of body weight.

3. Urinary excretion and skeletal deposition of F¹⁸ were similar regardless of whether the stable fluoride dose was 0.5 µg or 10 mg. per kilogram, indicating that there was no level of fluoride intake below which all ingested fluoride would be excreted.

4. There appeared to be genuine fecal excretion of F¹⁸, although the amount excreted by this route was quite small.

5. Absorption of orally administered F¹⁸ was not complete nine hours after its administration. At this time there was about 10 per cent of the administered dose in the cecum, large intestine contents, and feces.

6. The distribution of F¹⁸ in the rat was essentially the same whether it was given orally or by vein.

7. The distribution of F¹⁸ in the soft tissues of the rat was not significantly affected by the age of the animals. In contrast, the F¹⁸ uptake of the teeth and bones was definitely lower in mature rats than in young adults.

8. The extent to which a bone will accumulate F¹⁸ seemed to depend upon the vascularity of the bone and on its growth activity.