Christoffersen J, Christoffersen M R, Kolthoff N, Bärenholdt O
Institute for Medical Biochemistry and Genetics, Faculty of Health Sciences, University of Copenhagen, Denmark.
Bone. 1997 Jan;20(1):47-54. doi: 10.1016/s8756-3282(96)00316-x.
Preparation and analyses of a series of hydroxyapatites (HA) containing 1-10 mol % of Ca2+ replaced by Sr2+ is reported. The solubility of these apatites is found to increase with increasing content of Sr2+, 10% SrHA dissolves faster than CaHA at given values of Ca2+ and phosphate concentrations, but with a similar rate at the same degree of saturation. Sr2+ is found to inhibit the rates of both dissolution and growth of CaHA and 10% SrHA at pH 7.2, CaHA being more strongly inhibited by Sr2+ than 10% SrHA. The effect of partial substitution of Ca2+ in hydroxyapatite by Sr2+ on bone mineral content (BMC) and bone mineral density (BMD) measured by dual energy X-ray absorptiometry has been studied using three commercial densitometers. Extrapolating the absorption data for up to 10% replacement of Ca2+ by Sr2+ to 100% substitution of Ca2+ by Sr2+ in HA leads to an apparent increase in BMC or BMD of about a factor of 10. This factor is in agreement with theoretical calculations using attenuation coefficients of the atoms concerned. It is concluded that existing BMC scanners register artificially high values of BMC if the bone contains significant amounts of Sr2+ or other metal ions with atomic number larger than calcium.
本文报道了一系列钙（Ca²⁺）被锶（Sr²⁺）部分取代（取代量为1 - 10摩尔%）的羟基磷灰石（HA）的制备与分析。研究发现，随着Sr²⁺含量的增加，这些磷灰石的溶解度升高。在给定的Ca²⁺和磷酸盐浓度下，10% SrHA比CaHA溶解得更快，但在相同饱和度下溶解速率相近。在pH 7.2时，Sr²⁺会抑制CaHA和10% SrHA的溶解及生长速率，且CaHA受Sr²⁺的抑制作用比10% SrHA更强。利用三台商用骨密度仪，研究了Sr²⁺部分取代羟基磷灰石中Ca²⁺对通过双能X射线吸收法测量的骨矿物质含量（BMC）和骨矿物质密度（BMD）的影响。将Ca²⁺被Sr²⁺取代量高达10%时的吸收数据外推至HA中Ca²⁺被Sr²⁺ 100%取代的情况，结果显示BMC或BMD明显增加约10倍。该倍数与使用相关原子衰减系数的理论计算结果一致。研究得出结论：如果骨骼中含有大量Sr²⁺或其他原子序数大于钙的金属离子，现有的BMC扫描仪会记录到人为偏高的BMC值。
