Effects of Promotors and Inhibitors on In Vitro Crystallization of Calcium Oxalate in Agarose Gel Media

Park, Won Hee; Lee, Chongwook

Abstract

Three main mechanisms are thought to be important in the formation of urinary stones: 1) the relationship between the concentration of the precipitating substances in urine and the solubility of the mineral phase formed, 2) the role of promotors of crystallization, and 3) the part played by inhibitors of crystallization. In this experiment, we tried to know their roles and the relationship between the promotor and the inhibitor on calcium oxalate crystallization. We studied the promotion for calcium oxalate crystallization using the agarose gel model. The seed crystals of monosodium urate, brushite, and hydroxyapatitie were used as the promotor. The result was that calcium oxalate crystallization was significantly promoted and the level of its promotion was proportionally increased in addition of seed crystals. The promoting activity of hydroxyapatitie was maximum, then brushite, monosodium urate in order at pH 5.5. Scanning electron microscopy revealed calcium oxalate monohydrate growing on the surface of seed crystals. This process was thought to be the epitaxial growth. We studied the role of well-known inhibitors in the promoting process by 3 seed crystals. Heparin inhibited the promoting process of calcium oxalate crystallization by a seed crystal of monosodium urate but didn't inhibit that by 2 seed crystals of calcium phosphate. Pyrophosphate is a well-known inhibitor. However, in our experiment it was ineffective in simple calcium oxalate crystallization and the promoting process by any seed crystal. It was thought to be due to its inefficient diffusion into the gel because of its large molecule.