The Effect of Dietary Phosphorus on the Metabolism of Calcium and Strontium in the Rat

Summary

An investigation has been made of the way in which changes in dietary phosphorus within the physiological range influence the comparative metabolism of calcium and strontium in the rat. Radioactive calcium and strontium were used as tracers.

The absorption of both calcium and strontium after oral administration was dependent on the phosphorus level in the diet, but not to the same degree. The skeletal ratio ⁸⁵Sr/⁴⁷Ca decreased by some 40 per cent as the dietary phosphorus was increased from 0·5 to 1·3 g per cent.

After intraperitoneal injection of radioactive calcium and strontium, the skeletal retention of ⁸⁵Sr was about 25 per cent more on a diet containing 1·3 per cent phosphorus than on a diet containing 0·5 per cent phosphorus. Skeletal retention of calcium varied little.

It is concluded that renal discrimination against strontium as well as intestinal absorption of calcium and strontium were affected by the phosphorus content of the diet, but in opposite directions.