Total urine antioxidant capacity.

Total antioxidant capacity has been determined for several body fluids and provides a convenient means to compare antioxidant defenses among patients with acute or chronic inflammatory illnesses. We have studied urine specimens from a control group and a variety of patients with hypertension and acute and chronic renal diseases using an ABTS antioxidant assay as described for blood. Other urine assays included fluorescence markers for advanced glycosylation end products (AGE) and di-tyrosine (di-tyr), protein, uric acid, and creatinine concentrations. Urine antioxidant activity was standardized against ascorbic acid. We found that both the lag time and the area under the curve (AUC) in the ABTS assay were highly correlated with one another and correlated with the protein and uric acid concentrations, except for those specimens collected from patients with acute renal failure (ARF). The lack of correlation in the ARF group was not associated with significant differences in lag time or AUC. Correlations were seen also between antioxidant parameters and fluorescence for AGE and di-tyr. The results indicate that the predominant antioxidants in the urine of patients with acute renal failure differ from those found in the urine of individuals with hypertension and chronic nephropathies. The ABTS assay provides a convenient marker for the antioxidant content of urine.