Effect of Doubling the Oral Intake of Calcium on the Uptake of Radioactive Strontium in Rats

Abstract
Rats of two age-groups fed from weaning on a diet of constant composition were given a constant daily dose of 45Ca and 85Sr incorporated in the diet. In young rats (5 to 19 weeks old) increase of the calcium-intake from 0·56 to 1·1 g per cent decreased the skeletal retention of radioactive strontium by 45 per cent. In adults (16 to 26 weeks old) there was no change in the radioactive strontium deposited in bone when the calcium intake was doubled. The renal clearance of 85Sr increased with age and was also higher in rats on the higher calcium-intake. The overall discrimination between strontium and calcium, diet to bone, was not only age dependent but also showed a marked change when the calcium-intake was doubled.