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.
Highlights
The epithelial layer lining the intestinal tract represents a barrier that protects the host against harmful substances, prevents microbes from entering the body, and thereby contributes to maintaining host integrity
Our results demonstrate that the uptake of 4-kDa fluorescein isothiocyanate-conjugated (FITC) dextran in C3H/HeOu mice mainly occurred in duodenum and jejunum
To determine the site of 4-kDa FITC dextran uptake in the intestinal tract of C3H/HeOu mice, we monitored its concentration in plasma of one set of mice
Summary
The epithelial layer lining the intestinal tract represents a barrier that protects the host against harmful substances, prevents microbes from entering the body, and thereby contributes to maintaining host integrity. The relationship between gut barrier integrity and metabolic diseases has been investigated comprehensively by measuring gut permeability using different marker molecules such as non-digestible 4-kDa dextran conjugated with fluorescein isothiocyanate (FITC dextran) [2,3] Once orally administered, this fluorescent marker transits the gastrointestinal tract and passively crosses the intestinal epithelium. The time elapsed between oral application and maximal concentration of 4-kDa FITC dextran in plasma as well as gut-transit time of this marker have not experimentally been determined for this mouse model It is not known, where in the gut the 4-kDa FITC dextran is taken up and whether this marker determines small intestinal or rather colonic permeability in C3H/HeOu mice. C3H/HeOu mice measures permeability in these two small intestinal segments
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