利用同步辐射X射线吸收近边光谱检测SD大鼠血清中钙的形态

Blood calcium has been known to exist in three forms: the protein-bound Ca2+, the ultrafiltratable Ca2+ complexed by small anions, and the free Ca2+ ions that are believed to be physiologically active. The last two species are also present in serum that is the remained liquid after separating cells, fibrinogen, and coagulation factors from the blood. Since 1990s, researchers have detected kinds of particles of protein-inorganic complexes in serum-containing culture media, as well as in the media from certain patients. Moreover, we recently detected an amorphous phase of calcium carbonate in freshly prepared human blood serum. To find out if there is a correlation between the calcium species distribution in serum and the developmental stages using a rat model, we are to design and build a set of instrument on Beamline 4B7A at Beijing Synchrotron Radiation Facility, which is suitable for the detection of X-ray absorption near-edge structure spectroscopy of biological samples. And by this instrument, we are to investigate (1) the distribution of serum calcium species of rats in various growth and developmental stages; and (2) the alterations of the distribution incurred by some pathological processes. The implementation of the project may reveal the correlation between the calcium species distribution in serum and the rat developmental stages and, therefore, contribute to the promotion of health science.

在血液中存在三种形态的钙：与蛋白结合的钙、与一些阴离子结合的可滤过性钙和水合钙离子。除去血液中的细胞、纤维原和凝血因子后的液体称为血清，它主要含有后两种形态，其中水合钙离子是直接参与生理活动的形态。自从1990年代以来，人们发现固相无机物与蛋白的复合体能在含血清的培养基中形成，甚至从某些患者体内分离得到了类似颗粒物。我们最近从新鲜制备的人血清中也检测到了无定形碳酸钙。为了以大鼠为模型、考察血清中钙的形态分布与生长发育以及某些疾病之间是否存在相关性，本项目拟在北京同步辐射装置4B7A 光束线建立一套适用于检测液体生物样品近边光谱的装置，用以考察在不同生长发育阶段大鼠血清中钙的形态分布，以及一些生理和病理过程引起的改变。该项目的实施将有助于阐明血清中钙的形态分布与生长发育和某些疾病之间的关系，对于发展生物医学和保障人民健康具有重要意义。

三种形态的钙以特定比例存在于人体血清中：自由钙（fCa，45%）、与蛋白结合钙（prCa，40%）和与小分子结合钙（cCa，15%）；其中，fCa和cCa也常被称作可滤过性钙（uCa）。在一些病理状态下，prCa和cCa的组成会发生改变。例如，肾病患者呈高磷血症，导致prCa中的Ca2+结合了更多的无机磷（Pi），其含量被视为血管钙化的风险因子。本项目的主要目的是考察肾衰状态下各种形态钙的含量和组成的变化。我们采用大鼠模型检测了正常和肾病状态下的钙分布和相应的无机磷含量，主要研究结果如下：（1）获得了血清钙的K-边X射线吸收光谱，为血清cCa成分中的Ca(η2-HPO4)(H2O)4和Ca(η1-HCO3)(H2O)5+提供了光谱学证据；（2）在肾衰模型大鼠血清中检测到无定形磷酸钙；通过在血清中分别补加Ca2+和Pi，得到了prCa含量与Ca2+和Pi浓度的定量关系；（3）根据Ca2+和HPO42-反应的实验数据，提出了沉淀反应伪平衡方程的普遍形式。以上研究结果充实了血液生物化学的内容，有助于更深刻地认识相关生理学和病理学现象。