The effect of dietary fluoride on calcium and phosphorus metabolism of rats

Abstract

Two groups of 12 weanling rats were fed for 4 weeks diets containing 0.2 and 200 p.p.m. fluoride. All rats were then injected with 45CaCl2 and a week later a balance trial was conducted. At the end of the trial the rats were killed, and long bones, liver, kidney, and plasma collected. There were no significant differences between the two groups in the endogenous fecal Ca or absorption or retention of calcium, but the percent retention of phosphorus by the high fluoride group was 15% greater than that by the controls. Although fluoride feeding did not affect the ash, calcium, and phosphorus contents of the bones or the turnover of bone mineral, it caused a significant increase in the water content and a decrease in the breaking load of the femur shafts. When the effect of body weight on bone strength was eliminated from the fluoride group, there was no significant difference in the breaking load. The level of fluoride in the soft tissues of the treated rats was 3 to 8 times that in the corresponding tissues of the controls. The alkaline phosphatase activity in the bone and plasma of the treated rats was higher and the acid phosphatase activity in bone lower than the comparable values for the controls.