L. MiRAVET, D. Hioco: Transfert du calcium intestinal chez I'liomme 193 



permit further analysis of the disappearance curve in terms of both accretion and 

 excretion. 



In the cases studied, the '^^Ca abundance in pre-injection urine Ca as well as in 

 samples at the end of the experiment was similar to the abundance of the standards 

 used. There was no evidence of biological fractionation of ^^Ca. 



Discussion 



Because of a reluctance to employ radioactive tracers In young children-particu- 

 larly normal children, little Is known about the kinetics of calcium metabolism In 

 young normal subjects. Calculation of the 24 hour exchangeable calcium pool based 

 upon the 24 hour specific activity of radioactive calcium isotopes gave a value of 

 440 mg/Kg in seven normal one-year-old infants studied by Hoffenberg et al. 

 (1964) using ■*^Ca. Data from Bronner et al. (1956) on eight adolescent boys using 

 ^^Ca gave a pool size of 291 ± 54 mg/Kg Ideal weight. Eight normal adults under age 

 50 years (mean age 36 years) studied by Dymling (1964) with ^^Ca had a 24 hour 

 exchangeable calcium pool of 86.5 ± 20 mg/Kg. The relation of these values to the 

 data from this study Is shown In Fig. 3. 



Conclusions 



Stable ^''Ca in enriched form may be used as a tracer In dilution studies of calcium 

 kinetics in young children and other radiosensitive subjects. In the 10 cases studied, 

 the 24 hour exchangeable calcium pool relative to body weight was three to four 

 times as high as in normal adults. 



References 



Bronner, F., R. S. Harris, C. J. Maletskos, and C. E. Benda: Studies of calcium meta- 

 bolism: the fate of intravenously injected radiocalcium in human beings. J. clin. Invest. 

 35, 78 (1956). 



Dymling, J.-F.: Calcium kinetics in osteopenia and parathyroid disease. Acta med. scand. 

 Suppl. Vol. 175 (1964). 



FioFFENBERG, R., F. FiARRis, and E. Back: Ca-*' in the investigation of rickets. Medicals 

 uses of Ca*^ Second Panel Rep. IAEA, Tech. Rep. Ser. 32 Vienna 1964. 



McPherson, G. D.: Stable calcium Isotopes as tracers in studies of mineral metabolism. Acta 

 orthop. scand. Suppl. 78 (1965). 



Transfert du calcium intestinal chez I'homme dans les maladies 

 demineralisantes de I'os 



L. MiRAVET, D. Hioco 



Centre du metabolisme phospho-calcique, Flopital Lariboisiere, Paris, France 

 (Groupe Recherches I.N.S.E.R.M.) 



Pour explorer le transfert du calcium Intestinal chez I'homme, nous avons effectue, 

 en utilisant la technique simplifiee d'AuBERT et Milhaud (1960), 218 explorations 

 chez 5 sujets normaux et 182 sujets attelnts des maladies sulvantes: 39 osteoporoses com- 

 munes, 29 osteoporoses Idlopathiques, 2 maladies de Lobstein, 7 osteomalacles d'apport 

 (5 fois sans traltement et 4 fois sous calciferol), 9 osteomalacics par diabete phosphore 



3'''' Europ. Symp. on Cal. Tissues J3 



