In vivo FiTC-dextran permeability
This assay is an indirect measure of total intestinal permeability.
Permeability assays usually use oligosaccharides of large size. The large size molecule is thought to cross the paracellular intestinal pathway only if the intestinal barrier function is compromised.
In case of barrier function loss such probes cross the intestinal barrier, appear into the circulation and can be detected in urine after renal excretion. The small size molecule is thought to traverse the intestinal barrier freely, independent of barrier function loss, and is affected in the same way as the large molecular probe by the pre- and postmucosal confounders like as gastric dilution, gastrointestinal motility, bacterial degradation, and renal function.