Abstract: Sera and urine from patients with severe uremia and healthy subjects were seperated by means of gel permeation chromatography on Sephadex G15 column with N(C₂H₅)₃ H₂CO₃ buffer as eluent. Two middle molecular peaks(A and B) were detected at 206 nm in normal urine, uremic serum and uremic urine, but these two peaks were hardly observed in the profile of normal sera. In contrast, the absorption at 206 nm of fractions Aand Bfrom uremic serum and urine were less than that of fractions Aand Bfrom normal urine. Fractions Afrom normal urine, uremic serum and urine were collected and resolved into 8 to 9 subpeaks at 230 nm by anion exchange chromatography. One of these subpeaks, A-3, was detected in uremic serum and normal urine but undetectable in uremic urine. After a gel permeation chromatography with bidistilled water as eluent for desalting, subfraction A-3 was seperated into two parts designated A-3-Ⅰ and A-3-Ⅱ in order. The results of MALDI-TOF-MSrevealed that the two peaks from both samples were identical respectively, fraction A-3-Ⅰ contained three kinds of components with molecular weight 839.69, 1007.94 and 2015.16 and fraction A-3-Ⅱ consisted of other three kinds of components with molecular weight 873.69, 1106.67 and 1680.28.

Key words: Uremic, Middle molecule, Gel permeation chromatography, Anion exchange chromatography, Matrix assisted laser desorption/ionization time-of-flight mass spectrometry