Detection and characterization of modified nucleosides in serum and urine of uremic patients using capillary liquid chromatography-frit-fast atom bombardment mass spectrometry.

To determine RNA metabolism in uremia, capillary liquid chromatography-frit-fast atom bombardment mass spectrometry was employed for the characterization of ribonucleosides in serum and urine of uremic patients, and the profiles were compared with those of healthy subjects. We have characterized 20 nucleosides in serum and 23 nucleosides in urine from both healthy subjects and uremic patients; most of them were modified nucleosides derived from tRNA breakdown products. Four metabolites derived from allopurinol were detected as exogenous nucleosides in patients receiving allopurinol; these include allopurinol-1-riboside, oxipurinol-1-riboside, oxipurinol-7-riboside and a unknown oxipurinol riboside. The endogenous and exogenous ribonucleosides were retained at higher levels in uremic serum, and may play a contributory role as toxins responsible for clinical symptoms of uremia.