Effect of urinary macromolecules on aggregation of calcium oxalate in recurrent calcium stone formers and healthy.

The inhibitory activity of urinary macromolecules on the aggregation of calcium oxalate crystals was studied using an aggregometer originally devised to measure thrombocyte aggregation capacity by means of the optical turbidity at 660 nm. The macromolecular fraction of the urine (molecular weight above 5000) of recurrent calcium stone formers showed much less inhibitory activity than that of healthy controls (P < 0.05). It was speculated on the basis of the results of gel filtration that there were some proteins (molecular weight about 10,000-30,000) which had inhibitory activities for the aggregation of calcium oxalate. This gives support to the assumption that macromolecules are important during the phase of aggregation of calcium oxalate crystals.