Small Intestinal Permeability and Gut-Transit Time Determined with Low and High Molecular Weight Fluorescein Isothiocyanate-Dextrans in C3H Mice

Abstract

Protocols for intestinal permeability measurements in mice using 4-kDa fluorescein isothiocyanate-conjugated (FITC) dextran differ considerably among laboratories on the blood-sampling time. To find the optimal point in time for blood sampling, we administered 4-kDa FITC dextran to C3H mice and monitored the marker in plasma over 8 h. We also determined gut-transit time using 70-kDa FITC dextran, which does not cross the intestinal epithelium. The 4-kDa FITC dextran concentration in plasma reached its maximum 45 min after administration. The 70-kDa FITC dextran reached the jejunum after 15 min and passed the entire small intestine within 1 h after its administration, demonstrating that 4-kDa FITC dextran measured in plasma 1 h after its oral application is a marker of small intestinal permeability.

Keywords: FITC dextran; intestinal permeability; transit time.

Figure 1

Concentration of 4-kDa fluorescein isothiocyanate (FITC) dextran in plasma of C3H mice. The fluorescent marker was administered orally and its concentration was monitored over 8 h. Mean ± SEM, n = 3.

Figure 2

Levels of 70-kDa FITC dextran (●) and 4-kDa FITC dextran (×) in luminal contents of stomach (S), five small intestinal segments, caecum (Cc) and two colonic segments measured directly after gavage (0 min) and 15, 30 and 45 min and 1, 1.5, 2, 3 and 8 h after gavage. Each dot represents one mouse.