Isolation and characterization of an endogenous drug-binding inhibitor present in uremic serum.

Isolation of an endogenous ligand solute from uremic serum was performed by high-performance liquid chromatography. This ligand solute inhibited the binding of diphenylhydantoin and tryptophan to plasma protein, and was considered to be one of the endogenous drug-binding inhibitors present in uremic serum. The gas chromatographic-mass spectrometric analysis revealed that this inhibitor is 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, which is known to be a constituent of urine.