Aggregation of calcium oxalate crystals: Effect of urine and various inhibitors

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Abstract
The influence of various factors on aggregation of calcium oxalate crystals in vitro was determined. Aggregation was assessed by filtering the crystal suspension and measuring the flow rate through a filter. 10% urine completely inhibited aggregation. Orthophosphate and magnesium at concentrations occurring in urine had no effect. Citrate had no effect at 10-4 M, but did inhibit at 10-3 M. The latter effect is probably due to calcium binding. Pyrophosphate and disodium dichloromethylene diphosphonate (Cl2MDP) inhibited strongly at 10-4 M, disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) at 10-5 M, whereas pentanemonophosphonate had no effect. Uromucoid also did not show any inhibitory activity. Studies by means of heat inactivation, ultrafiltration and fractionation on DEAE-cellulose and gel-filtration indicated that the inhibitory activity was heterogenous and that the major part was larger than 10000 daltons.