Gastrointestinal permeability to polyethylene glycol: an evaluation of urinary recovery of an oral load of polyethylene glycol as a parameter of intestinal permeability in man.

The permeability of the gastrointestinal tract was investigated by means of polyethylene glycol (PEG), given orally. The PEG solutions contained oligomers with molecular weights from 414 to 1206. The urinary recovery of ingested PEG was determined by high performance liquid chromatography (HPLC). Considerable inter- and intra-individual variations in recovery were found in a reference group of 33 healthy subjects. Intake of food did not change the recovery of PEG, 6.11% (SEM 0.52, n = 13) compared with that for the reference group, 6.45% (SEM 0.39, n = 33). The PEG recovery in a group of ileostomy patients was 5.86% (SEM 0.62, n = 13). No correlation was found between PEG recovery and small bowel transit time. The lipophillic properties of PEG were determined by measuring the partition coefficients in 1-octanol/water and in methylhexanoate/water systems. From these results, correlated with the values for the hydrodynamic volumes of PEG, it was concluded that the intestinal permeation of PEG observed was probably determined by the hydrophillic/hydrophobic properties of the mucosal membrane, rather than by the presence of intercellular junctions or paracellular pores. The PEG molecules with molecular weights from 414 to 1206 were, therefore, not suitable as solitary probes for permeability studies in man.