Effect of Varying Calcium Intake on the Parameters of Calcium Metabolism in the Rat

Abstract

Kinetic tracer techniques providing the data for a compartmental analysis were supplemented with Ca balance measurements to obtain the rates of Ca absorption, endogenous fecal excretion, exchangeable space and accretion rates. The effect of low and high Ca diets was measured in terms of the above-measured parameters of skeletal metabolism in rats. Varying the Ca intake had no effect on the size of the compartments in the model used. Further, while the accretion rate of Ca into bone was not affected by the dietary Ca level, the rate of feedback of Ca from bone was quite sensitive to the level of Ca in the diet. The low Ca diet resulted in an appreciable increase in the resorption rate of Ca from bone and a very low rate of apposition of Ca into bone. However, the high Ca diet resulted in a minimal resorption rate (actually a negative rate) and a large increase in the net deposition of Ca in the skeleton. The use of a mathematical model proved to be a useful framework against which the effects of various Ca intakes could be measured quantitatively.