[Inhibitory activity of urinary macromolecule upon calcium oxalate crystal aggregation using an aggregometer]

We studied inhibitory activity of urinary macromolecule upon the calcium oxalate crystal aggregation using an aggregometer. We have developed an aggregometric assay method to measure the anti-aggregation ratio of calcium oxalate crystals in vitro. The macromolecular fraction of urine with a molecular weight above 5,000 was isolated by PD-10 (Sephadex G-25M, Pharmacia) and made up to three-fold by Centriprep Concentrator (Amicon). The urinary macromolecular substances of recurrent calcium stone formers showed much less inhibitory activity than those of healthy controls. There were no significant relationships between the anti-aggregation activity and the concentration of urinary proteins and other parameters concerning with stone diseases. It was speculated that some proteins, molecular weight about 10,000-30,000, might inhibit the aggregation vigorously based on the result of gel filtration (Superrose 12 HR, 20/50, Pharmacia) technique used in a healthy man's 24 hours urine. Thus, it supports that some urinary macromolecules are important during the phase of aggregation of calcium oxalate crystals, and that the feeble activity to present the aggregation may be one of the cause of calcium oxalate stone formation.