钙是人体的必需元素，参与众多的生命生理调控过程。骨钙的流失可以导致骨质疏松症（OP）等多种疾病，补钙成为流行。但最近的研究表明生物体（特别是骨质疏松生物体）摄入过量的钙可能会引起一些其它疾病。因此，准确测量生物体的钙吸收率，对于合理补钙和预防钙代谢疾病具有重要意义。传统的钙吸收率测定方法存在着钙源区分不清、测量灵敏度低、放射性损伤等问题，难以开展准确、系统、长期的研究工作。本项目利用加速器质谱技术测量长寿命放射性核素Ca-41灵敏度高的特点，通过Ca-41标记体内钙库的新方法，开展正常及骨质疏松大鼠对钙吸收率的准确测定。通过标准化的模型建立、示踪方法与测定，Ca-41体内钙库标记方法可以从根本上解决传统生物示踪技术的不足。本项目将系统研究影响钙吸收的因素，准确测定钙吸收率，从而为合理补钙、建立适宜于中国人的钙参考摄入量标准提供研究基础。

Calcium is an essential element that plays important roles in physiologic adjustment for human body. The losses of calcium content of bone will cause osteoporosis and other diseases. Calcium supplement is becoming more and more popular. However, recent studies have shown that some other diseases may be caused by excess calcium supplement（especially for patients with osteoporosis）.So, the accuracy of calcium absorption rate measurement is very meaningful for reasonable calcium supplement and prevention diseases of calcium metabolism. Due to the poor distinction of calcium source, lower measurement sensitivity and radioactive damage, etc for the traditional calcium absorption rate measurement technique, it is difficult to carry out the accurate, system, long-term research work. Based on the high sensitivity of Ca-41 measurement with accelerator mass spectrometry and the innovative methods of Ca-41 labeling endogenous calcium, the calcium absorption rate of normal and osteoporosis rats will be studied in this work. With the standard rat model, tracing and measurement, the labeling endogenous calcium with Ca-41 can fundamentally solve the shortage of traditional biological tracer technique. The project will systematically study influence factors on calcium absorption and accurately determine the calcium absorption rate. These studies can provide the basis for reasonable supplement of calcium and calcium intakes reference for Chinese people.