Endothelial injury and regeneration. IV. Endotoxin: a nondenuding injury to aortic endothelium.

Groups of rats were injected with endotoxin (Escherichia coli, 3 mg. per kg. of body weight) over a 10-minute period and perfusion fixed at 0.5, 1, 2, 4, 8, 18, 20, 24, 48, 72, and 96 hours later. Studies on aortic endothelium of these animals revealed no endothelial cell denudation and no exposure of the subendothelium. By 20 hours a large number of cells was observed attached to the intact endothelial monolayer, and some of these cells could be identified as desquamating endothelial cells. Autoradiographs revealed a marked increase in endothelial cell replication between 24 and 96 hours. Since there was no change in the number of cells per unit area, these data indicate that endotoxin in the rat produces desquamation with simultaneous replacement by cell movement and cell replication.