Uremic middle molecules: analytical study of middle molecular weight fractions subpeak b4-2

Fractions containing substances weighing less than 1800 daltons have been obtained from hemofiltrate and peritoneal dialysis fluid. Oligosaccharides and glycopeptides were evidenced in these fractions by paper chromatography. This analytical procedure has been applied to a fraction containing peak b4-2 obtained by molecular exclusion chromatography on Sephadex G-15 followed by ion exchange chromatography on Sephadex A-25 (Cueille et al.). Preparative paper chromatography of this fraction evidenced 3 carbohydrate and 3 peptidic fractions. Study of the carbohydrate fraction (01, 03, 04) by gas-chromatography and mass spectrometry shows that they are composed of glucuronoconjugates whose aglycons have not been identified. Fraction 04 which contains subpeak b4-2 has been found to have an inhibitory effect on the action potentials of the sural nerve of the frog.