The examination of the epithelial barrier has been a primary site of focused research for years. Despite the importance of this site to numerous intestinal diseases, the determination of the integrity of this barrier has been clouded by controversies as to the validity of certain techniques and the ease of use regarding others. To determine the barrier integrity in vivo, we have adapted a simple tracer-based microscopic assay that was initially used in other systems to the in vivo intestinal epithelium. This technique is widely adaptable to other tracer molecules that can be applied to the tissue and consequently generates images depicting barrier maintenance or functional breach.
