Impact of various modifiers on calcium oxalate crystallization

OBJECTIVE: This work focuses on the behavior of in vitro calcium oxalate crystallization. The effects of several compounds on the kinetics of calcium oxalate crystallization were examined. METHODS: Rates of nucleation and aggregation of calcium oxalate crystals were derived from 30-min time-course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at 37 degrees C, pH 5.7. The maximum increase of optic density with time, termed S(N), mainly reflects maximum rate of formation of new particles and thus crystal nucleation. After equilibrium has been reached, optic density decreases. No new particles were formed due to crystal aggregation. S(A) (the maximum slope of decrease of optic density at 620 nm with time, representing crystal aggregation) is derived from the maximum decrease in optic density. RESULTS: Among the modifiers studied, citrate decreased both S(N) and S(A) (P < 0.001). Magnesium was also found to inhibit the rate of nucleation and crystal aggregation, but it appeared in a non-concentrated manner. Nucleation and aggregation inhibition ratios were related inversely to concentration of albumin (P < 0.001). CONCLUSION: The growth and agglomeration of calcium oxalate crystals are differently modulated by various compounds. The treatments aiming at inhibiting crystallization of calcium oxalate can be better defined by these findings. And new treatment modalities can be developed.