A new method for D-glucaric acid excretion measurement that is suitable for automated instruments

Urinary excretion of D-glucaric acid (uGA) is an index of type II hepatic microsomal enzyme induction, indirectly revealing possible organic effects of some drugs and environmental pollutants. However, its determination is often cumbersome. We suggest a new, fast microanalytical method for uGA determination in which beta-glucuronidase (BG; EC 3.2.1.31) activity inhibition produced by uGA-derived 1,4-D-glucarolactone is measured. With use of purified BG, the method is suitable for centrifugal analyzers, allowing assay of greater than 100 samples per day. Moreover, the method measures uGA more accurately than other enzymatic methods based on BG inhibition. The within-day CV ranges from 7.9% to 4.6% (uGA 31.55-121.31 mumol/L); the between-day CV ranges from 11.5% to 5.0% (uGA 26.09-124.10 mumol/L). The detection limit is 6.0 mumol/L. The standard curve is linear from 10 to 200 mumol/L. Mean analytical recovery is 100%. Comparison with the method of Simmons et al. (Clin Chim Acta 1974;51:47-51) gave a correlation of r = 0.978, y = 1.40x-2.81. Reference intervals were established in a healthy population sample of 369 people (165 under 14 y), and uGA, expressed in micromoles per gram of creatinine, was higher in women than in girls or in males.