Application of the Miles Assay to Study Microvascular Permeability in Ischemia–Reperfusion Injury of the Small Intestine

Abstract

Abstract—The Miles assay using Evans Blue dye is a conventional method to assess vascular permeability. The penetration Evans dye into intestinal tissue was studied in the early reperfusion phase of ischemia–reperfusion injury to the small intestine. Significant destruction of villus microvessels and an increase in vascular permeability to plasma proteins were observed in the early reperfusion phase, impairing the blood flow at the microvasculature level based on evidence from histology and laser Doppler flowmetry. Evans Blue accumulated to the highest concentration in intestinal tissue after being injected into the bloodstream prior to 60-min ischemia; the lowest level was detected when the dye was injected after 15-min reperfusion. Changes in the dye content in intestinal tissue therefore depended on the number of vessels that remain intact at the time of dye injection at various stages of ischemia–reperfusion. Evans Blue observed in tissue was assumed to reflect the degree of vessel preservation in a study of ischemia–reperfusion injury of the small intestine, rather than reporting the degree of vascular permeability, as commonly believed.