mepositomy 84 RECORD? CoLLection MARSHALL BoxNe. MEDICAL DEPT Reprinted from JoURNAL oF APPLIED PHysioLoGy Vol. 21, No. 1, January, 1966 Printed in U.S.A, wy Q, /SZANOS coz ie PUBLICATIONS Fepem 22/52 — 323 Strontium and calcium skeletal discrimination determined by compartmental analysis’ 401 B25 yy transfer of Sr and Ca between plasma and boneor within Coun, 8. H., 8. R. Bozzo, J. E. Jessep, C. ConsTANTINIDES, E. A. GusMANO, AND J. S. RoBERTSON. Strontium and calcium discrimination determined by compartmental analysis. J, Appl. Physiol. bone, however, has not been conclusively demonstrated in vivo. It is the object of this study to determine whether discrimination between Sr and Ca byskeletal tissue does at(1): 67-72. 1966.—A multicompartmental-type analysis was used to describe metabolic data obtained in a double tracer experiment in man and to compare the quantitative differences exist and, if so, to quantify the differences. In addition to the interest in Sr as a tracer for Ca, there has been considerable attention to the metabolism of Sr ‘ in the values of the parameters obtained with Ca and Srtracers. The compartmental sizes and transfer constants and their stand- per se. However, the metabolism of Sr in a biological system is described most effectively in terms of the ard deviations were obtained with the NIH-OMR-SAAM program and an 1BM-7094 computer. ‘To obtain data beyond the 10-day period in which plasmaactivity could be measured, a whole-body counter and a collimated external detector were employed. The absolute values of the various parameters obtained with Sr were slightly lower than those obtained with Ca, comparative Sr and Ca kinetics for, while Sr metabolism is apparently not under direct homeostatic control, it nevertheless appears to be influenced by the Ca level. Differences in the kinetic behavior of the two elements reflect the basic physiological processes responsible for their differential movementin the body. In the present study, multicompartmental analysis but the Sr-derived values did reflect the Ca metabolism very well in terms of the assumed model for the to-day data. The whole-body counter data collected over 30 days indicated differences in the whole-body and bone turnover of Sr and Ca, suggesting differences in resorption and long-term exchange of was used to describe the metabolic data so that quantita- tive differences in the values of the parameters could be Ca compared with Sr which are not apparent in the to-day used to compare the kinetics of Sr and Ca metabolism. A ‘ OMR SAAM program using an IBM-7094 computer. The model was shown to have a high degree of unique- ness in its fit of the data. With this model and computer As THEREIs no long-lived gamma-emitting radioisotope of calcium, a substitute is required. Because of the chemical similarity of calcium and strontium, radioactive program, the data obtained with Sr®> and Ca‘? simul- taneously administered to a numberof subjects were also analyzed. In order to obtain data beyond the 10-day Sr has commonly been used as a tracer in Ca metabolic period in which plasma activity can be measured, a studies. Notwithstanding the chemical similarity of Sr and Ca, physiological differences have been shown to exist, particularly in those processes which involve metabolic transfer across membranes. Ca is transferred preferentially to Sr in gastrointestinal absorption, renal excretion, lactation, and placental transfer (g). In-vitro studies (12, 14) have suggested that discrimination by skeletal tissue may also exist. Such discrimination in the whole-body counter was employed. In addition, a collimated detector was used to measure the activity in a bone compartment (knee) to provide further data on the turnover of the tracers. METHODS Subjects. Seven male subjects ranging in age from 53 to 80 years of age received doses of Sr®* and Ca‘? simultaneously. All of the subjects received a physical examina- Received for publication 19 April 1965. 1 This research was supported by the US Atomic Energy Commission, i mya 9UP2 705 tion as well as essential laboratory and X-ray studies 67 ee published data) to represent the kinetics of injected Ca‘? and applied in a study of parathyroid deficiency (6). The compartment sizes and transfer constants and their standard deviations were obtained with the NIH- Mineral metabolism; calctum and strontium kinetics; compartmental model for calcium and strontium; computer analysis of tracer kinetic data Ee aae two-compartment model was previously formulated (un- Her study. rahdenttnar Dpton, L. L, New York C. CONSTANTINIDES, E. A. GUSMANO, AND J. 5. ROBERTSON . Medical Research Center, Brookhaven National Laboratory, Upton, Long Island, New York LL Brookhaven National Labocaiacy S. H. COHN, S. R. BOZZO,J. E. JESSEPH, A gt eMthy SRE i The Medical Research Crneer