A Gel Model for Measuring Crystallization Inhibitor Activities

Abstract

We devised a simple and economical technique for measuring crystallization inhibitory activities. Calcium ions and oxalate ions diffuse towards one another from two adjacent wells in a layer of gel on a microscope slide. Where they meet, a streak of calcium oxalate crystals forms. Substances which influence crystallization are caused to diffuse into this middle zone. Depending on the inhibitory potency of the substance, the calcium oxalate streak varies in density and extent. These differences are recorded photometrically by comparison with a sample containing no inhibitor, and the inhibition index is calculated. Some of the best known inhibitors were tested and showed a definite effect in this model. Magnesium and citrate in physiological concentrations are of special significance. The expected range of variation of inhibitory activities in human urine is covered by this method.