An improved method for gas chromatographic determination of urinary xylitol and glucuronic, glucaric gulonic and ascorbic acids, with their values in the rat, rabbit, guinea-pig and marmoset

Urinary D-glucaric acid, a marker substance for microsomal enzyme induction. Methodological aspects, responses to alcohol and findings in workers exposed to toluene

D-glucaric acid, an end product of glucuronic acid metabolism, has been used as a marker substance for microsomal enzyme induction. In this study a convenient microtitre-plate based method for the quantification of urinary D-glucaric acid has been developed and validated. Mean urinary D-glucaric acid excretion in 20 health humans as measured by this method was 3.2 mumol glucaric acid mmol-1 creatinine, 95% confidence interval 3.0-3.4. Moderate alcohol consumption in 18 healthy volunteers did not significantly augment the urinary D-glucaric acid excretion. Occupational exposition to toluene in a printing plant was investigated. In spite of considerable intra- and inter-individual variability, a significant difference between exposed (3.5, 3.1-3.9) and non-exposed (2.6, 2.2-3.0) workers was observed, p < 0.025. We conclude that the measurement of D-glucaric acid can be utilized for biological screening of enzyme induction on a group basis.

Studies on the biochemical effects of the aldose reductase inhibitor 2,7-difluorospirofluorene-9,5'-imidazolidine-2',4'-dione (Al 1576, HOE 843). Detection of D-glucaric and D-glucuronic acid excretion by high resolution 1H and 13C NMR spectroscopy

The effects of two aldose reductase inhibitors on the biochemical composition of rat urine were investigated using high resolution 1H and 13C NMR spectroscopy. We report the elevated excretion of D-glucaric acid (DGA) and D-glucuronic acid (GCA) following treatment with 2,7-difluorospirofluorene-9,5'-imidazolidine-2'4'-dione (Imirestat, IM, Al 1576, HOE 843) at 50 mg/kg/day for 1 month, but not with 3-4-bromo-2-fluorobenzyl-4-oxo-3-phthalazine-1-ylacetic acid (Ponalrestat, Statil), dosed at 50 mg/kg/day for 2 weeks. Sugar aciduria was also detected following treatment with the cytochrome P450 inducer phenobarbitone (PB) at 45 mg/kg/day for 1 month, although the qualitative and quantitative pattern of excretion of sugar acids differed greatly between the IM and PB treatment groups. The levels of GCA excreted are elevated 11-fold by IM treatment from 19.0 to 210.0 mumol/24 hr, but only 2.5-fold by PB, from 9.7 to 23.9 mumol/24 hr. DGA was not detectable in control urine, although levels did increase by 30% during the study from 7.5 to 10.9 mumol/24 hr, between day 8 and day 29, with IM treatment, and by 60% from 1.7 to 4.9 mumol/24 hr following PB administration for the same time period. This predominant elevation of DGA and GCA caused by IM treatment far exceeds previous records. In contrast, PB treatment resulted in an increase in intensity of a number of partially resolved sugar resonances, but at a much lower level than resulted from IM treatment. A raised level of DGA and GCA is usually associated with hepatic P450 induction; however, we report here profound DGA and GCA uria as a result of the inhibition of the aldehyde reductase, hexonate dehydrogenase (EC 1.1.1.19, EC 1.1.1.20). This mechanism is not closely linked to P450 induction, corroborating the current view that elevated excretion of DGA is not a reliable indicator of hepatic enzyme induction. This study further demonstrates the use of high resolution NMR spectroscopy in the detection of a novel biochemical effect which may go unnoticed during routine clinical chemistry tests.

The excretion of metabolites of the D-glucuronic acid pathway in human urine. Effect of phenobarbitone administration

1. The urinary excretion of four metabolites of the D-glucuronic acid pathway, namely D-glucaric acid, free (unconjugated) D-glucuronic acid, L-gulonic acid and xylitol, has been studied in normal male volunteers and in male and female epileptic patients receiving phenobarbitone anticonvulsant therapy. 2. In normal male subjects the urinary excretion of the D-glucuronic acid metabolites, expressed per unit of creatinine, was similar in first void and total (24 h) urine samples and was fairly constant over a period of 4 weeks. 3. In male and female epileptic patients phenobarbitone treatment enhanced the urinary excretion of D-glucaric acid and xylitol and the combined excretion of D-glucaric acid, l-gulonic acid and xylitol. 4. It is suggested that the measurement of a spectrum of urinary D-glucuronic acid metabolites may provide a more reliable index for assessment of the induction of hepatic xenobiotic-metabolizing enzyme activities in man than the determination of urinary D-glucaric acid alone.