The nucleation, growth and aggregation of calcium oxalate(CaC 2O 4) crystals were comparatively investigated in five different mimetic systems: water, NaCl solution, artificial urine, healthy urine and lithogenic urine by using scanning electron microscopy(SEM). The effects of original concentration of calcium ion and oxalate ion and crystallization time on the morphology, density and the size of CaC 2O 4 crystals were discussed. In lithogenic urine, calcium oxalate monohydrate(COM) crystals were the dominant phase. However, a mixture of COM and calcium oxalate dihydrate(COD) with a molar ratio of about 3∶2 was obtained in the healthy urine. COD has a less affinity for renal tubule cell surface, so COD is easy to be expelled out from body and there is a less probability of stone-forming in the healthy urine. The fastest nucleation and growth of CaC 2O 4 crystals were obtained in water and NaCl solution, respectively. The size of CaC 2O 4 crystals decreases in the following order: NaCl solution>artificial urine>lithogenic urine>healthy urine>water.
The effects of urinary macromolecul e chondroitin sulfate A(C 4 S)and L-glutamic acid(L-Glu)on the crys-tallization of calcium oxalate were studied using Langmuir-Blodgett(LB)film of dipalmitoylphosphatidylch oline(DPPC)as templet.All the calcium oxalate c rystals induced by the LB film of DPPC were calcium oxalate monohydrate(COM).However,the morphology of COM was i nfluenced by the additives of C 4 S and L-Glu.C 4 S induced thin and long hexagonal COM c rystals;L-Glu made one or two (010)crystal face of COM crystals dis-appeared.The crystallization time had no effect on the morphology of COM crystals,but the concentration of C 4 S and L-Glu changed it.As increasing the co ncentration of C 4 S,the amount of COM crystals with a hexagonal prism decreased and that with a thin hexago nal slice increased.When the concen tration of C 4 S was 0.50mg ·mL -1 ,all the calcium oxalate crystals were th in hexagonal slice COM crystals.How ever,as the concentration of L-Glu in-creased from 0.01to 0.50mmol·L -1 ,the hexagonal prism-like COM crystals gradually transformed to COM crystals with one or two (010)crystal face disappearance.
The effects of counterions of citric acid and EDTA on the crystallization of calcium oxalate(CaO x )were in-vestigated in silica gel with a doubl e diffusion technique.The ability o f inhibiting the growth and aggregation of CaO x crystal and the ability of inducing f ormation of COD follows:potassium c itratesodium citrate >citric acid.Na 2 EDTA had a stronger ability to inhibi t the aggregation of CaO x crystals than that of EDTA,but a weak er ability to inhibit nucleation and growth of C aO x crystals.Since COM exhibits a greater degree of attachment to renal tubule cells in culture compared with COD,t hat is,COD is easy to be expelled from the body along with the urine.So both inducing formation of COD and in hibiting growth and aggregation of CaO x crystal can decrease the probability of urinary stones.These results hav e positive significance in the prevention and cure of urinary stones clin ically.
