The effects of low and high molecular weight substances on citrate — induced changes of growht and agglomeration of calcium oxalate crystals

Abstract

The processes of crystal growth and agglomeration have for a long time been treated as one entity, mainly because of a lack of methods in which the two processes could be measured separately. Substances working on the measured crystallization rates by binding to the crystal surface, were termed inhibitors of growth and agglomeration. However, we have previously shown that a substance may inhibit crystal growth and at the same time stimulate crystal agglomeration (1,2). Also, comparing urine from a selected group of recurrent calcium oxalate stone formers with urine from a group of healthy subjects, we found that the strong inhibition of crystal agglomeration in the normal urine was absent from the stone formers’ urine, while crystal growth was inhibited to the same extent in both groups (3). The defect in agglomeration inhibition was associated with an abnormally low citrate excretion in the stone former group. Increase in urine citrate content in vitro or in vivo resulted in increased agglomeration inhibition, while crystal growth inhibition remained unaffected (4,5). Thus in urine the processes of crystal growth and crystal agglomeration, although they are both crystal surface related, seem to be affected by different (groups of) compounds. For the present paper we studied the effects of a low and a high molecular weight compound on calcium oxalate crystal growth and agglomeration and their respective relationships to citrate.