Serum oxalate in human beings and rats as determined with the use of ion chromatography

Previous enzymatic determinations have suggested that serum oxalate concentrations in normal rats, the main animal model used in urolithiasis research, to be 3 to 5 times greater than those in healthy human subjects. In this report we validated this observation using a different method (ion chromatography) on serum samples from healthy rats and human subjects that were prepared and handled similarly. Oxalate recoveries during sample preparation for ion chromatography were strongly and variably affected by ultrafiltration devices employed for sample deproteinization and after Cl(-) removal by means of ion exchange. When oxalate recoveries were accounted for, we found significant differences in serum oxalate (6 human samples, 1.47 +/- 0.15 micromol/L; and 15 rat samples, 9.88 +/- 0.91 micromol/L). We conclude that ion-chromatographic techniques confirm the differences in serum oxalate concentrations between rats and human beings measured enzymatically and that failure to account for oxalate losses during sample preparation for ion chromatography can lead to significant underestimation of serum oxalate in both species.