Modelling of intestinal permeability in man to polyethylene glycols (PEG 400 and PEG 1000)

The intestinal permeability barrier was evaluated in four healthy individuals by the 6 h urinary recovery of a mixture of different-sized polyethylene glycols (PEG 400 and PEG 1000) after a liquid meal of probe molecules. The mixture of PEGs contained around 25 different PEG polymers, ranging from about 194 to 1294 dalton in size. Three models were employed to get a condensed formulation of the intestinal barrier, namely a filter function, describing exclusion of molecules due to the molecular weight, and two expressions for ultrafiltration through a pore due to the Stoke-Einstein radius. A factor reflecting unrestricted passage of probe molecules in the size-range used was also included in the mathematical expressions. It was found that a filter function showing half-maximum exclusion at 589-956 daltons (Da) PEG and a pore function yielding a pore-size of 8.0-8.5 A equally well described the intestinal barrier in the four subjects. The results are discussed in relation to structures of the intestinal epithelium that may restrict the passage of molecules.