Bone mass increase and glucose tolerance in rats chronically treated with sodium fluoride.

Female rats were treated with fluoride for 100 days (between 21 and 121 days of age) replacing the water supply with a 5 mM NaF solution. Bone mass was assessed by destructive physical and chemical measurements on the whole skeleton, that gave an overall view not reported previously. Bone mass (dry, fat-free weight of the skeleton/100 g of body weight) increased 7% (P less than 0.001) with respect to control animals. This phenomenon was equally evident in the head, the axial and the appendicular skeleton. Fluoride treatment did not affect the ratio ashes/organic matrix. Treated animals showed a subtle disturbance of glucose tolerance as shown by glucose tolerance tests. The disturbance was manifest as high plasma and soft tissue levels of fluoride during the period of bone mass increase. Glucose tolerance was normalized when the maximum bone mass was achieved and plasma and soft tissue fluoride returned to control levels.