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Fan HX, Gou BD, Gao YX, Wu G, Liu SH, Li F, Zhang TL. Protein-bound calcium phosphate in uremic rat serum: a quantitative study. J Biol Inorg Chem 2020; 25:1051-1063. [PMID: 32839886 DOI: 10.1007/s00775-020-01807-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 08/04/2020] [Indexed: 10/23/2022]
Abstract
Protein-bound calcium (prCa) constitutes about 40% of serum total calcium, in which albumin is the most dominant protein. Given the chemical interaction between calcium and phosphate (Pi), the increased serum Pi in chronic kidney disease may cause changes in the composition and structure of the prCa fraction. Here, we report the phosphate binding on the protein-bound calcium in uremic rat serum. Using adenine-fed rats as a uremic model, we separated the calcium and phosphate fractions in rat serum by ultrafiltration, and found that the level of protein-bound phosphate (prPi) in the uremic serum was markedly higher than in control. The elevated prPi level was comparable to the prCa level, consistent with the presence of protein-bound calcium phosphate pr(Ca)j-m(CaPi)m. We then confirmed its presence by ex vivo X-ray absorption near-edge structure spectroscopy, revealing the discrete state of the calcium phosphate clusters associated with protein. Finally, in a quantitative investigation using Ca- and Pi-boosted serum, we discovered the threshold concentration for the Pi binding on prCa, and determined the binding constant. The threshold, while preventing Pi from binding to prCa in normal condition, allows the reaction to take place in hyperphosphatemia conditions. The protein-bound calcium phosphate could act as a link between the metabolism of serum proteins and the homeostasis of phosphate and calcium, and it deserves further investigation whether the molar ratio of (prPi/prCa)⋅100% may serve as a serum index of the vascular calcification status in chronic kidney disease.
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Affiliation(s)
- Hong-Xing Fan
- Department of Preclinical and Forensic Medicine, Baotou Medical College, Inner Mongolia University of Science & Technology, Baotou, 014010, People's Republic of China.,CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049, People's Republic of China
| | - Bao-Di Gou
- Department of Chemical Biology, Peking University School of Pharmaceutical Sciences, 38 Xueyuan Road, Beijing, 100191, People's Republic of China
| | - Yu-Xi Gao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049, People's Republic of China
| | - Gang Wu
- Department of Preclinical and Forensic Medicine, Baotou Medical College, Inner Mongolia University of Science & Technology, Baotou, 014010, People's Republic of China.
| | - Shu-Hu Liu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049, People's Republic of China
| | - Fan Li
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049, People's Republic of China
| | - Tian-Lan Zhang
- Department of Chemical Biology, Peking University School of Pharmaceutical Sciences, 38 Xueyuan Road, Beijing, 100191, People's Republic of China.
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Fan HX, Gou BD, Gao YX, Wu G, Zhang TL. Pseudo-equilibrium equation of calcium phosphate precipitation from aqueous solution. Phys Chem Chem Phys 2019; 21:22057-22066. [DOI: 10.1039/c9cp04250d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For a precipitation reaction involving an amorphous phase, the equilibrium equation takes the general form (middle), which converts to the conventional “reaction quotient” (left) and the “solubility product” (right) in two limit cases, respectively.
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Affiliation(s)
- Hong-Xing Fan
- State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control
- Beijing Synchrotron Radiation Facility
- Institute of High Energy Physics
- Chinese Academy of Sciences
- Beijing 100049
| | - Bao-Di Gou
- Department of Chemical Biology
- Peking University School of Pharmaceutical Sciences
- Beijing 100191
- P. R. China
| | - Yu-Xi Gao
- State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control
- Beijing Synchrotron Radiation Facility
- Institute of High Energy Physics
- Chinese Academy of Sciences
- Beijing 100049
| | - Gang Wu
- Department of Biochemistry
- Baotou Medical College
- Inner Mongolia University of Science & Technology
- Baotou 014010
- P. R. China
| | - Tian-Lan Zhang
- Department of Chemical Biology
- Peking University School of Pharmaceutical Sciences
- Beijing 100191
- P. R. China
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