BACKGROUND: Intestinal permeability is determined by measuring nonmetabolized sugars. In animals, intestinal permeability is determined in urine, using cumbersome and expensive metabolic cages. We developed an HPLC method for determining concentrations of lactulose (L) and L-rhamnose (R) in blood-drop of rabbits and mice, and we compared these results with the procedure based on sugars excreted in urine. We measured the intestinal permeability induced by a fragment (DeltaG) of the zonula occludens toxin which opens the paracellular pathway. METHODS: The animals received sugar solution and later received the same solution+DeltaG. Five-hour urine collection and timed blood tests were performed after ingestion of sugars. Sugars were measured with HPLC, and the percentage of recovered sugars was expressed as L/R ratio. RESULTS: At 60 min after administration of sugars, the mean L/R ratio for rabbits and mice was 0.026 and 0.052, respectively. At 60 min after administration of sugars+DeltaG, the mean L/R ratio for rabbits and mice was 0.22 and 0.53. The mean L/R ratio in the urine was 0.023 at basal condition and 0.25 after DeltaG ingestion. CONCLUSIONS: Testing small serum samples for sugar permeability is effective for monitoring changes in permeability of the gut in animals. This cheap simple method allows us to measure in vivo the biological activity of other molecules which modulate the paracellular pathway.
