The Age-Dependence of Strontium Retention in Rats and Mice

Abstract

It is ordinarily assumed, from consideration of the growth process, that strontium -or for that matter, most of the bone-seeking elements-is more efficiently retained by young, growing animals than by adults. The literature contains ample support of this conclusion. However, only a few studies are available that demonstrate the quantitative relationships between retention of bone-seeking elements and age. Carlsson (1) found that bone formation (accretion), as measured by Ca45 uptake in rats, was directly related to the rate of increase in body weight. Glad et al. (2) reported that Sr85 is better retained in 6-month-old dogs than in more mature animals and that the rates of excretion were age-dependent for as long as 200 days after administration. Studies of strontium retention after a single administration to animals of various ages are needed to provide more exact descriptions over extended periods of time. Such results should allow the formulation of mathematical models to predict skeletal strontium burdens resulting from continued or repeated exposures over known age intervals. This requires, of course, that tractable expressions for retention as a function of age can be postulated.