Effect of Trace Metals on In Vitro Crystallization of Calcium Oxalate in Agarose Gel Media

Abstract

Trace metals are components of urinary stones, though minute and exist also in normal urine. There have been many studies concerning the role of these materials in crystallization. In this experiment we examined the role of trace metals and the effect of interaction of trace metals and promotors in crystallization of calcium oxalate. We used the agarose gel model with 3 layered structure and added trace metals in various concentrations into the upper layer of oxalate solution. The seed crystals of monosodium urate, brushite, and hydroxyapatite were used as the promotor and added to the middle layer of agarose gel. The lower layer was the agar containing calcium ions. These test tubes were incubated at 3TC and crystals formed in middle layer were extracted and dried on previously determined time schedule. These crystals were analysed qualitatively and quantitatively. The X-ray diffractogram of these extracts revealed only whewellite. Iron (III), aluminum(lIl), copper(II), and zinc(ll) were proved to inhibit crystallization of calcium oxalate. And the inhibitory activity was proportional to the concentration of these trace metals. These inhibitory activities were about 40%, 40%, 25%, and 25%, respectively in 0.01 M of trace metals (CaCI2: trace metal = 10: 1 molar ratio). Tin(ll) did not inhibit simple crystallization of calcium oxalate, but significantly inhibited the promoting process by 3 seed crystals.