Glyoxylate determination in rat urine by capillary electrophoresis

Oxalate is important in the study of renal stone formation and is derived from the endogenous metabolism of glyoxylate. The aim of this study was to determine urinary glyoxylate levels by capillary electrophoresis (CE). Urine specimens were obtained from 25 male Wistar rats (16 rats intravenously injected with 10 mg or 20 mg glyoxylate and nine controls) by bladder puncture 1 h after administration of glyoxylate or saline. Urinary glyoxylate was measured by CE using an electrolyte composed of 5 mmol/L pyridinedicarboxylic acid and 0.5 mmol/L cetyltrimethylammonium bromide (pH 5.6 and 11.0). The mean +/- SD urinary glyoxylate concentration was 43.1 +/- 14.7 micromol/L in control rats, 722.8 +/- 165.5 micromol/L in rats given 10 mg of glyoxylate and 1290.0 +/- 470.8 micromol/L in rats given 20 mg of glyoxylate. The mean +/- SD recovery after spiking 675.7 micromol/L of glyoxylate into 16 urine specimens was 98.82 +/- 12.81%. When the reproducibility of urinary glyoxylate determination was assessed, the intra-assay coefficient of variation (CV) ranged from 1.38 to 2.59% and the inter-assay CV ranged from 2.94 to 6.69%. Capillary electrophoresis enables sensitive and reproducible determination of urinary glyoxylate levels in rats. This method appears to be suitable for laboratory use and has the advantage of determining glyoxylate and several other urinary anions simultaneously.