Pancreatic calcification: formation constants of CaHCO3+ and CaC03(0) complexes determined with Ca2+ electrode

Abstract

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.

A Straightforward Treatment of Activity in Aqueous CaCO3 Solutions and the Consequences for Nucleation Theory

“…The observation of linear ion binding behavior prior to nucleation (Figure ) has been used to argue that association is limited to simple ion pairs . This notion was inferred by considering a chemical equilibrium between multiple ions (here n Ca 2+ + n CO 3 2− [CaCO 3 ] n ), for which it can easily be shown that at a large excess of one of the involved ions (CO 3 2− in the present experiments), the other (Ca 2+ ) can only be bound with n = 1 for linear profiles to be obtained (i.e.…”

Pathophysiological preconditions promoting mixed “black” pigment plus cholesterol gallstones in a ΔF508 mouse model of cystic fibrosis

“…Furthermore, we did not observe any evidence of CaCO 3 crystals when gallbladder biles of ⌬F508 and WT mice were examined microscopically. Moore and Vérine (46,47) demonstrated that the formation constants of Ca(HCO 3 ) 2 and CaCO 3 are also promoted by gallbladder acidification of hepatic bile; hence, in CF it is likely that these salts could contribute to black pigment gallstone formation (9). Since ion product data showed both skewness and kurtosis, the MannWhitney test was used to calculate statistical significance.…”

Pathophysiological basis of liver disease in cystic fibrosis employing a ΔF508 mouse model

“…2C and D, respectively). It is unlikely that Ca or Fe precipitated with carbonate or phosphate since the pH of hepatic bile is not consistent with supersaturation with Ca salts of these anions (47,48). Moreover, conjugated bile salts, even glycine-conjugated ones, are resistant to Ca precipitation in the typical concentrations found in hepatic bile (24,39).…”