Abstract
Tamm-Horsfall protein (THP) and human serum albumin (HA) are common urinary proteins which show variable inhibitory ability on the crystallization of calcium oxalate monohydrate. Post-translational modification of THP with sialic acid was reported to have effect on the inhibition of crystal aggregation. Batch crystallization experiments of crystal nucleation, crystal growth, and aggregation were performed for the study of influence on cryastallization by THP and HA under conditions of native and enzymatic deglycosylation of sialic acid. The result indicates that both THP and HA can promote the crystal nucleation. THP and HA exerted inhibitory effect of the crystal growth and crystal aggregation in the following studies. The inhibition was decreased after enzymatic removal of the sialic acid from THP. Whereas HA show little change after enzymatic treatment. So the inhibition effect of THP is partly related with the presence of sialic acid.Oxalate caused by tubular cellular damage by the production of free radicals can induce cell death and cellular debris may promote the retention of calcium oxalate crystal and finally the formation of stones. THP and HA were both tested for the effects of antioxidants through study of xanthine-xanthine oxidase reaction. The data indicates that the THP and HA have an antioxidant effect with IC50 at nM of THP and nM of HA. But the effect was decreased after enzymatic deglycosyation of sialic acid. So the inhibitory effect of both proteins may result partly from glycosylation and is associated with calcium oxalate formation. In conclusion, THP and HA show an overall effect of inhibition in vitro. According to Cerini's hypothesis, both proteins could be inhibitors of calcium oxalate crystallization, due to its enhancing nucleation and decrease crystal growth, aggregation and prodcution of free radicals. The inhibition effect of THP and HA are partly related with the presence of sialic acid. Studies have indicated that a further investigation of the role of free radicals in the formation of urolithiasis and role of sialic acid.