Measuring Intestinal Permeability with FITC-Dextran

Plasma was diluted 1:5 (v/v) in PBS. Gut contents were diluted 1:10 or 1:100 (v/v) with PBS for the 70-kDa or 4-kDa FITC dextran analyses, respectively. Fluorescence was measured spectrophotometrically (Infinite M200 PRO, Tecan, Crailsheim, Germany) in 96-well plates (excitation: 485 nm, emission: 528 nm). FITC dextran concentrations were calculated with the help of standard concentrations prepared in PBS ranging from 0 to 250 µg/mL 4-kDa FITC dextran or 0 to 1250 µg/mL 70-kDa FITC dextran. Emission signals in plasma and gut contents of the mice receiving PBS were subtracted from those of mice treated with the 4-kDa or the 70-kDa FITC dextran. The fluorescence signal of luminal 70-kDa FITC dextran in each segment was related to the sum of the fluorescence signals in all segments of the gastrointestinal tract.