Moore E W, Verine H J
Am J Physiol. 1981 Aug;241(2):G182-90. doi: 10.1152/ajpgi.1981.241.2.G182.
Pancreatic calcification is a frequent complication of chronic pancreatitis, and pancreatic stones (95% CaCO3 as calcite) are observed in both humans and cattle, but little is known about the complex equilibriums governing calcium solubility. Using the Ca2+ electrode and equilibrium dialysis of NaHCO3-CaCl2-NaCl solutions (24 +/- 2 degrees C; total ionic strength = 0.153-0.161), studies were made at variable pH and total calcium and carbonate concentrations to determine the formation constants of the three possible calcium complexes: CaHCO3+, CaC03(0), and Ca(HCO3)20. If the first two complexes were present, a plot of ([Ca]/[Ca2+]-1)/[HCO3-] against the ionic ratio [C03(2)-]/[HCO3-] should be linear with intercept of the CaHCO3+ formation constant (K'aB) and slope of the CaC03(0) formation constant (K'aC). This was found to be the case in both dialysands and dialysates, using two different methods ("pH" and "K'sp") for estimation of [CO32-] values. Two other methods of data analysis were also used: simultaneous equations and multiple linear regression by matrix analysis. For all three methods, mean K'aB = 12.48 and mean K'aC = 1,870. There was no evidence for a Ca(HCO3)2(0) complex. We conclude that CaHCO3+ and CaC03(0) complexes may account for a substantial fraction of total soluble calcium is pancreatic juice. These studies provide a necessary step toward the construction of a quantitative physicochemical model of pancreatic calcium solubility.
胰腺钙化是慢性胰腺炎的常见并发症，在人类和牛中均观察到胰腺结石（95%的碳酸钙为方解石），但对于控制钙溶解度的复杂平衡知之甚少。使用钙离子电极以及对NaHCO₃ - CaCl₂ - NaCl溶液进行平衡透析（24 ± 2℃；总离子强度 = 0.153 - 0.161），在不同的pH值、总钙浓度和碳酸盐浓度下进行研究，以确定三种可能的钙络合物的形成常数：CaHCO₃⁺、CaCO₃⁰和Ca(HCO₃)₂⁰。如果前两种络合物存在，([Ca]/[Ca²⁺] - 1)/[HCO₃⁻]对离子比[CO₃²⁻]/[HCO₃⁻]的作图应呈线性，其截距为CaHCO₃⁺的形成常数（K'aB），斜率为CaCO₃⁰的形成常数（K'aC）。使用两种不同的方法（“pH”和“K'sp”）估计[CO₃²⁻]值时，在透析物和透析液中均发现情况确实如此。还使用了另外两种数据分析方法：联立方程法和矩阵分析多元线性回归法。对于所有三种方法，平均K'aB = 12.48，平均K'aC = 1870。没有证据表明存在Ca(HCO₃)₂⁰络合物。我们得出结论，CaHCO₃⁺和CaCO₃⁰络合物可能占胰液中总可溶性钙的很大一部分。这些研究为构建胰腺钙溶解度的定量物理化学模型迈出了必要的一步。
