Inhibition of calcium oxalate crystallization by commercial human serum albumin and human urinary albumin isolated from two different race groups: evidence for possible molecular differences

This study was undertaken to investigate the inhibitory activity of urine-derived (as opposed to serum-derived) albumin towards calcium oxalate crystallization and to compare the relative inhibitory strengths of this protein in subjects from South Africa's black and white population groups. Albumin was purified from the urines of 20 males in each race group using immunoaffinity chromatography. The purified proteins, as well as commercial human serum albumin were tested for their inhibition of calcium oxalate crystallization in ultra-filtered urines from both groups. Irrespective of its origin, albumin was found to be an inhibitor of calcium oxalate aggregation. Albumin derived from black subjects was superior to that from white subjects in this regard while urine-derived albumin was superior to that derived from serum. The composition of the urine in which the experiments were conducted influenced the inhibitory activity of the individual proteins. The different inhibitory activity of the proteins under identical conditions provides evidence that suggests molecular differences exist between them.