Identification and quantification of a protein-bound ligand in uremic serum

A major protein-bound ligand in the serum of chronic hemodialysis patients was isolated from heat-deproteinized uremic serum by "high-performance" liquid chromatography (HPLC). The isolated compound was identified as 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid by use of liquid secondary-ion mass spectrometry and gas chromatography-mass spectrometry. On HPLC, an authentic sample of this compound showed a retention time identical to that of the protein-bound ligand peak. The concentration of the furancarboxylic acid in serum, as estimated by HPLC, is markedly greater in chronic hemodialysis patients than in normal subjects.