Effect of Metal Ions on the Relative Uptake of Ca⁴⁵ and Sr⁸⁵ by Bone Powder in Vitro

¹ Veterans Administration Hospital, Hines, Illinois, and Montefiore Hospital, New York, New York

The ratio of uptake of Ca⁴⁵ to that of Sr⁸⁵ by defatted bone powder in vitro was used as a parameter for the study of bone surfaces. To test the hypothesis that one difference between sites where ions exchange was the space available on the crystal surface, defatted bone powder was treated with metallic ions of different radii and then shaken with solutions containing Sr⁸⁵ and Ca⁴⁵. Alternatively, the metal ions were added to the same solution as the radioisotopes. Uptake was determined both with defatted bone powder and with "anorganic" bone. The ratio of Ca⁴⁵/Sr⁸⁵ uptake was decreased by Be⁺⁺, Cu⁺⁺, Co⁺⁺, Ni⁺⁺, Mn⁺⁺, Cd⁺⁺, Zn⁺⁺, and Pb⁺⁺, unaffected by Mg⁺⁺, and increased by Ba⁺⁺. Other factors also influenced the ratio, but, in general, the hypothesis suggested above appeared valid. Reproducibility of individual uptake values, but not of the ratio, was increased by more vigorous shaking.