The organic matrix of urinary uric acid crystals

We have demonstrated that urinary uric acid crystals contain an organic matrix within the crystalline boundaries, morphologically similar to that of uric acid stones. Among several glycosaminoglycans in urine, heparan sulfate was almost exclusively identified in this matrix, as in that of uric acid stones. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that several proteins in urine were incorporated in this matrix on a selective basis; two of which were albumin and Tamm-Horsfall mucoprotein. An affinity of uric acid or urate for selective urinary macromolecules in a liquid phase was supposed to be the origin of this matrix. But the proteins in the uric acid stone matrix were not separated by SDS-PAGE. Therefore we could not conclude whether the organic matrix of urinary uric acid crystals is similar to that of uric acid stones.