Simulation In Vitro On Formation Of Calcium Oxalate Calculus In Presence Of Dicarboxylic Acids And Metal Ions

The effect of the series of dicarboxylic acids and metal ions on the crystallization of calcium oxalate was investigated in silica gel system. These acids include succinic acid, maleic acid and fumaric acid without substituted groups, malic acid with one hydroxyl group, aspartic acid with one amino group, tartaric acid with two hydroxyl groups. These metal ions include Na⁺,K⁺, Mg²⁺,Sr²⁺and La³⁺.The dicarboxylic acids with three C-C bonds distance could inhibit the growth and aggregation of calcium oxalate crystal. Acids which had the group HOOC-C(OH)-C-COOH or HOOC-C(NH₂)-C-COOH were always found to have the best inhibitory effect. Tartaric acid which had two hydroxyl groups was better than malic acid with one hydroxyl group, not only in inhibiting the aggregation of COM but inducing COD.Different effect of the metal ions(Na⁺, K⁺,Mg²⁺,Sr²⁺, La³⁺) on the crystallization of calcium oxalate was contrasted. Sr²⁺ could inhibit the growth of COM; La³⁺ could inhibit the growth and aggregation of COM. At the same time, the mixed additive (tartaric acid and metal ion) were studied. Mg²⁺, Sr²⁺, La³⁺ could enhance the effect of tartaric acid on inhibiting growth and aggregation of CaOxa crystal. Generally speaking, the ability of inducing the formation of COD follows: H₂tart-La(57%) > H₂tart-Sr(29%) > H₂tart-Mg(22%) >H₂tart-Na,K(15-16%).In the last section, the research system of biomineralization simulation in vitro was discussed. The growth and aggregation of CaOxa crystal in different gel systems (gelatin, agar gel and silica gel) were investigated. Gelatin could promote the nucleation of COM, inhibit the growth and aggregation of CaOxa crystal, and induce the formation of COD; this ability was enhanced along with the increase of the concentration. Polyhedral COM crystal was found in agar gel. In silica gel we could obtain typical hexagonal CaOxa crystal.In this paper, the mechanism of dicarboxylic acids and metal ions inhibiting CaOxa crystal was discussed. The results could provide theoretical bases for designing the new drug of acids or acids associating with metal ions in lithiasis.