Effect of Sodium Fluoride on the Ultra-structure of the Parathyroid Glands of the Sheep

Abstract

IN drinking-water, concentrations of fluoride in excess of 100 p.p.m. inhibit bone growth in experimental animals, and this effect has usually been explained as a local action of fluoride on bone¹. That fluoride acts in this way is certainly true in tissue culture². In the intact animal, however, large resorption cavities containing fibrous tissue and many osteoclasts are often seen in the long bones and vertebrae. These resorption cavities, which have received scant attention since their original observation by Roholm³, are difficult to explain as a purely local effect of fluoride: it is not easy to reconcile the fact that fluoride appears selectively to depress osteoblasts on one hand, yet concomitantly to stimulate osteoclasts on the other, despite the fact that these latter cells contain at least one enzyme—acid phosphatase—that is known to be inhibited by fluoride in vitro⁴. Furthermore, smaller concentrations of fluoride, given to rabbits, appeared to exert their effect on bone principally by reducing resorption⁵.