Pancreatic calcification and stone formation: a thermodynamic model of calcium in pancreatic juice.
Pancreatic calcification and stone formation: a thermodynamic model of calcium in pancreatic juice.
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胰腺钙化和结石形成：胰液中钙的热力学模型。
DOI：
10.1152/ajpgi.1987.252.5.g707
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Verine,HJ
中科院分区：
文献类型：
--
作者：
Moore,EW;Verine,HJ
碳酸钙是胰腺结石、唾液结石和许多色素胆结石的主要成分。阐明钙的物理化学状态对于确定钙在这些体系中的溶解度是必要的。胰腺结石在人类和牛身上都能观察到，在这两个物种中都有大约95%的CaCO3(方解石)。尽管它很重要，但人们对胰液中钙的物理化学状态知之甚少。本文根据已建立的物理化学原理，提出了一个关于果汁中钙在所有分泌物水平上的状态的先验模型。该模型的两个假设如下：果汁中的极限游离[Ca~(2+)]由CaCO_3的溶解度积(K‘_p)决定；如果K’_p超过，则果汁过饱和，CaCO_3沉淀是可能的；果汁中的总钙[Ca]是四种不同物种的总和：游离钙，Ca~(2+)；钙-碳酸氢盐络合物，CaHCO_3+；碳酸钙离子对，CaCO_3(0)；和蛋白质结合的钙，CaProt。给出了模型的总体方程和图解推论。该模型预测了[Ca~(2+)]或[Ca~(2+)]与[HCO3-]之间的反双曲线关系。钙的溶解度在低[HCO3-]时最大；随着[HCO3-]的增加，[Ca2+]和[Ca]都下降到分别约0.015和0.15mM的极限值。低[HCO3-]时，[Ca]主要以Ca~(2+)和CaProt形式存在，而高[HCO3-]时，大部分[Ca]以CaHCO3+和CaCO3(0)形式存在。因此，蛋白质、HCO3-和CO3(2-)离子是果汁中钙离子的重要缓冲。该模型为进一步阐明胰腺、唾液腺和胆道中钙的致石性提供了一个定量框架。
CaCO3 is a major constituent of pancreatic stones, salivary stones, and many pigment gallstones. Elucidation of the physicochemical state of calcium is necessary for definition of calcium solubility in these systems. Pancreatic stones are observed in both humans and cattle, and are approximately 95% CaCO3 (calcite) in both species. Despite its importance, little is known about the physicochemical state of calcium in pancreatic juice. This paper presents an a priori model, based on established physicochemical principles, for the state of calcium in the juice at all levels of secretion. Two postulates of the model are the following: the limiting free [Ca2+] in the juice is governed by the solubility product (K' sp) for CaCO3; if K' sp is exceeded, the juice is supersaturated and precipitation of CaCO3 is thermodynamically possible; total calcium, [Ca], in the juice is the sum of four distinct species: free ionized calcium, Ca2+; calcium-bicarbonate complex, CaHCO3+; calcium carbonate ion-pair, CaCO3(0); and protein-bound calcium, CaProt. Overall equations of the model and graphical corollaries are presented. The model predicts an inverse hyperbolic relationship between [Ca2+] or [Ca] and [HCO3-]. Calcium solubility is maximal at low [HCO3-]; as [HCO3-] increases, both [Ca2+] and [Ca] decline to respective limiting values of approximately 0.015 and 0.15 mM. At low [HCO3-], most of [Ca] is present as Ca2+ and CaProt, whereas at high [HCO3-], most [Ca] is CaHCO3+ and CaCO3(0). Protein, HCO3-, and CO3(2-) ions are thus important buffers for Ca2+ in the juice. The model provides a quantitative framework for further elucidation of calcium lithogenicity in the pancreas, salivary gland, and biliary tract.