Inhibitors of the growth and aggregation of calcium oxalate crystals in vitro

Abstract

A sensitive method has been developed for measuring the effect of inhibitors of crystallisation on the growth and aggregation of calcium oxalate crystals in vitro. Of the known inhibitors tested the highly charged anions pyrophosphate and ethane-1-hydroxy-1,1-diphosphonate (EHDP) were effective down to concentrations of 0.1–1 μmole/l and the polyanions heparin and chondroitin sulphate A down to concentrations of 1 nmole/l. Within the normal range of urea concentrations found in urine the neutral molecule urea caused a small but significant degree of inhibition. At higher concentrations the degree of inhibition increased sharply. In the concentrations tested the cations magnesium and methylene blue had no effect on the growth and aggregation of crystals. These findings suggest that highly charged anions and polyanions may have some clinical value as a possible treatment for recurrent calcium oxalate stone-formation in man.