RELATION BETWEEN INTESTINAL CALCIUM AND STRONTIUM ABSORPTION

Recently, stable strontium has been proposed for the determination of calcium absorption. In the present work we analyze resemblance between Ca and Sr absorption. The present study is aimed at providing a simpl e method of the estimation of true Sr absorption based on Sr content i n one blood sample. The investigation is based on data obtained after an oral administration of 152 mg (1.9 mmol) of Sr in healthy subjects. One of the subject was chosen for a more detailed study including adm inistration of 100 mg (2.5 mmol) of elemental Ca and radioactive 47Ca isotope. To the same subject Sr-85 was intravenously administered. Acc ording to the elaborated Theoretical model entire content of absorbed tracer is positioned in a pool, V(t), which is time dependent. Specifi c radioactivity in this pool is equal to serum specific radioactivity, os(t). So, the absorption can be calculated as the product of serum r adioactivity and a time depending Ca-pool, V(t),: Abs(t) = (100/S1 t(b ) 1/1 + F(t,Tz,b))o.s(t) As a golden standard for absorption estimatio n, numerical deconvolution method is applied using KONDEK computer num erical deconvolution program. The difference between Sr and Ca pool wa s within limits of experimental error Both pools had time dependent va lues. The present investigation demonstrated that the concept of an ex panding Ca -pool can be used in the description of serum radioactivity after oral administration, and the same concept could be suitable for the description of the exchange process between strontium in serum an d bone mineral. The authors believe that the presented model permit an accurate estimation of Sr absorption. They point out that from method ological viewpoint the Sr absorption test is not an expensive one and anticipate that Sr absorption test will become a method of choice for population studies of Ca absorption.