Trace metal-citric acid complexes as inhibitors of calcification and crystal growth. II. Effects of Fe(III), Cr(III) and Al(III) complexes on calcium oxalate crystal growth.

The high molecular weight Fe(III)-citric acid complex, formed at low ratios of citrate:iron in solution, has been shown to be an effective inhibitor of calcium oxalate crystal growth. This appears to be a specific reaction, since 2 other similar metal ions. Al(III) and Cr(III), exhibit no synergism with citric acid in this system. Because the low molecular weight Fe(III)-citric acid complex, formed at high ratios of citrate:iron, inhibits calcium phosphate precipitation but has no effect on calcium oxalate, the Fe(III)-citric acid system might have a selective biologic role in regulating the growth of calcium-containing urinary calculi in vivo.