Arteriolar injury and denudation of endothelium induced by FeCl₃. (a) Progression of FeCl₃-induced injury. Fluorescence intensity of endothelium of mesenteric arterioles (n = 14/group) from GFP-transgenic mice was blindly ranked from 5 to 0. FeCl₃-treated or untreated arterioles were then compared by Mann-Whitney U test. Before FeCl₃ treatment (0 min), all arterioles had a similar intensity (∼5). Significant differences were found after 1 minute of FeCl₃ exposure (P = 0.0006). After 2 minutes (not shown), the intensity in control vessels decreased only slightly (mean = 4.1), whereas in FeCl₃-treated vessels, fluorescence was greatly decreased (mean = 1.4; P = 0.0001). After 4 minutes, the fluorescence intensity in the control group was still high (mean = 3.4), but in the FeCl₃ group was almost undetectable (mean = 0.4; P < 0.0001). Representative photographs of one vessel from each group are shown. (b) Denudation of endothelium by FeCl₃. Control (∼130 μm diameter) and FeCl₃-treated (∼100 μm diameter) sections of mesenteric arterioles from wild-type mice were stained with rabbit anti-human vWF polyclonal Ab, which cross-reacts with mouse vWF. Endothelial cells in the control arteriole were heavily stained, whereas only a few areas were stained with this Ab (arrow) after 5-minute FeCl₃ treatment. These areas may be remaining endothelial cells or small thrombi. The brown ring at the inner side of the injured vessel wall may result from plasma vWF deposition or from subendothelial vWF.