Polymeric dyes: limitations in their use as reference markers in postcibal studies

Polyporphyre and polycyanine are polymeric dyes which were recently described as useful markers for intestinal perfusion studies. The dyes were examined in this study in regard to their suitability for postcibal studies. In comparison with polyethylene glycol (PEG) 4000, a widely used nonabsorbable marker, both dyes were quantitatively adsorbed to cooked liver particles. This in vitro finding was confirmed in dogs with midgut fistulas. After a meat meal, we observed complete uptake of polycyanine to food particles. Polycyanine furthermore showed color instability below pH 3. These results indicate that the dyes are inferior to PEG 4000 when solid food is present in the intestinal lumen.