Some aspects of uptake of strontium by calcium hydroxylapatite

Calcium hydroxylapatite (CaHA), Ca10(PO4)6(OH)2 which is also called bone mineral, is the principal inorganic constituent of human skeletal system. Ca2+ → Sr2+ substitution in hydroxylapatite is important since it explains the mechanism of incorporation of β-active 90Sr of atomic debris into the human skeletal system. This study was undertaken in order to determine the manner in which strontium is incorporated into the inorganic crystal phase of bone. Synthetic and natural calcium hydroxylapatites exchange calcium with strontium. Exchange rate (i)increases with increase in (Sr2+), (ii)decreases with the increase in the particle size of calcium hydroxylapatite and (iii)decreases with the increase in the pH in the range 5.0 to 8.0. At 100degC the strontium uptake is governed by adsorption and diffusion while at 25degC it is governed by the process of adsorption only. (author). 12 refs