EVANS BLUE-DYE MODIFIES THE ULTRASTRUCTURE OF NORMAL AND REGENERATINGARTERIAL ENDOTHELIUM IN RATS

Evans blue dye (EBD) identifies areas of increased vascular permeabili ty, which is usually indicative of endothelial damage, Most studies ex amine EBD-stained areas light-microscopically, but others analyze the cells with the electron microscope. Electron microscopic studies have assumed that EBD itself did not change the ultrastructure of endotheli al cells and this hypothesis was tested in the following study. The le ft iliac arteries of 20 rats were injured with 1-mm vascular clamps fo r 5 minutes, At 7 and 14 days after clamping, 10 rats for each time we re infused intravenously either with normal-saline or EBD, perfused 30 minutes later with fixatives, Then the clamp-injured arteries, contra lateral (unclamped) arteries, aortae, and the aortic bifurcations were removed for EM morphometry. In an additional (control) group of 10 ra ts, with no clamp injuries, 5 were infused with EBD and 5 with normal- saline and all 10 rats were perfused 30 minutes later, as above. EBD c aused a significant simplification of the junctional morphology in bot h normal and regenerating endothelium. It also increased the area frac tions of cytoplasmic vesicles in regenerating endothelium. These data demonstrate that EBD causes measurable ultrastructural changes in norm al and regenerating endothelium. This effect should be taken into acco unt when using EBD to assess various insults to blood vessels. (C) 199 8 Wiley-Liss, Inc.